104-555: The Original Chip Set ( OCS ) is a chipset used in the earliest Commodore Amiga computers and defined the Amiga's graphics and sound capabilities. It was succeeded by the slightly improved Enhanced Chip Set (ECS) and the greatly improved Advanced Graphics Architecture (AGA). The original chipset appeared in Amiga models built between 1985 and 1990: the Amiga 1000 , Amiga 2000 , Amiga CDTV , and Amiga 500 . The chipset which gave
208-413: A 16-bit repeating pattern to the line. The line mode can also be used to draw rotated bobs: each line of bob data is used as line pattern while the line mode draws the tilted bob line by line. The blitter's filling mode is used to fill per-line horizontal spans. On each span, it reads each pixel in turn from right to left. Whenever it reads a set pixel, it toggles filling mode on or off. When filling mode
312-421: A "dual-playfield" mode. Denise also handles mouse and digital joystick input. Paula is primarily the audio chip, with four independent hardware-mixed 8-bit PCM sound channels, each of which supports 65 volume levels (no sound to maximum volume) and waveform output rates from roughly 20 samples per second to almost 29,000 samples per second. Paula also handles interrupts and various I/O functions including
416-442: A chipset; it only continues to be present for interfacing with low speed I/O. AMD server CPUs adopt a self contained system on chip design instead which doesn't require a chipset. The northbridge to southbridge interconnect interfaces used now are DMI ( Intel ) and UMI ( AMD ). These can also be used for connecting from a processor to a chipset. Random-access memory Random-access memory ( RAM ; / r æ m / )
520-535: A dedicated text mode. Finally, Denise next to the CIAs is responsible for handling mouse/joystick X/Y inputs. The notion that Denise fetches bit plane and sprite data is a simplification. It is Agnus who is maintaining horizontal and vertical screen position counters and initiating the DRAM read operations. Denise has a number of bit plane registers which hold 16 bits of data each, enough to draw 16 pixels. When Agnus issues
624-563: A few dozen or few hundred bits of such memory could be provided. The first practical form of random-access memory was the Williams tube . It stored data as electrically charged spots on the face of a cathode-ray tube . Since the electron beam of the CRT could read and write the spots on the tube in any order, memory was random access. The capacity of the Williams tube was a few hundred to around
728-470: A hard drive. This entire pool of memory may be referred to as "RAM" by many developers, even though the various subsystems can have very different access times , violating the original concept behind the random access term in RAM. Even within a hierarchy level such as DRAM, the specific row, column, bank, rank , channel, or interleave organization of the components make the access time variable, although not to
832-424: A memory capacity that is a power of two. Usually several memory cells share the same address. For example, a 4 bit "wide" RAM chip has four memory cells for each address. Often the width of the memory and that of the microprocessor are different, for a 32 bit microprocessor, eight 4 bit RAM chips would be needed. Often more addresses are needed than can be provided by a device. In that case, external multiplexors to
936-404: A portion of a computer's RAM, allowing it to act as a much faster hard drive that is called a RAM disk . A RAM disk loses the stored data when the computer is shut down, unless memory is arranged to have a standby battery source, or changes to the RAM disk are written out to a nonvolatile disk. The RAM disk is reloaded from the physical disk upon RAM disk initialization. Sometimes, the contents of
1040-600: A programmed instruction stream, synchronized with the video hardware. When it is turned on, the Copper has three states; either reading an instruction, executing it, or waiting for a specific video beam position. The Copper runs a program called the Copper list in parallel with the main CPU . The Copper runs in sync with the video beam, and it can be used to perform various operations which require video synchronization. Most commonly it
1144-555: A relatively slow ROM chip are copied to read/write memory to allow for shorter access times. The ROM chip is then disabled while the initialized memory locations are switched in on the same block of addresses (often write-protected). This process, sometimes called shadowing , is fairly common in both computers and embedded systems . As a common example, the BIOS in typical personal computers often has an option called "use shadow BIOS" or similar. When enabled, functions that rely on data from
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#17327917969951248-542: A single MOS transistor per capacitor. The first commercial DRAM IC chip, the 1K Intel 1103 , was introduced in October 1970. Synchronous dynamic random-access memory (SDRAM) was reintroduced with the Samsung KM48SL2000 chip in 1992. Early computers used relays , mechanical counters or delay lines for main memory functions. Ultrasonic delay lines were serial devices which could only reproduce data in
1352-433: A single frame to increase the total sprites per frame. Sprite position registers may also be changed during a scanline, increasing the total number of sprites on a single scanline. However, the sprite data , or shape, is only fetched a single time per scanline and can't change. The first Amiga game to utilize the sprite re-position registers during a scanline was Hybris released in 1988. The Denise chip does not support
1456-491: A switch that lets the control circuitry on the chip read the capacitor's state of charge or change it. As this form of memory is less expensive to produce than static RAM, it is the predominant form of computer memory used in modern computers. Both static and dynamic RAM are considered volatile , as their state is lost or reset when power is removed from the system. By contrast, read-only memory (ROM) stores data by permanently enabling or disabling selected transistors, such that
1560-611: A thousand bits, but it was much smaller, faster, and more power-efficient than using individual vacuum tube latches. Developed at the University of Manchester in England, the Williams tube provided the medium on which the first electronically stored program was implemented in the Manchester Baby computer, which first successfully ran a program on 21 June, 1948. In fact, rather than the Williams tube memory being designed for
1664-498: A traditional northbridge to do so. Intel followed suit in 2008 with the release of its Core i series CPUs and the X58 platform. In newer processors integration has further increased, primarily through the inclusion of the system's primary PCIe controller and integrated graphics directly on the CPU itself. As fewer functions are left un-handled by the processor, chipset vendors have condensed
1768-444: A video mode with higher horizontal scan rate . Alternately, Paula may signal the CPU to load a new sample into any of the four audio output buffers by generating an interrupt when a new sample is needed. This allows for output rates that exceed 57 kHz per channel and increases the number of possible voices (simultaneous sounds) through software mixing. The Amiga contains an analog low-pass filter ( reconstruction filter ) which
1872-643: A write to register 1, all registers are then transferred into separate shift registers from which pixels are generated (at the same time new values are loaded from DRAM). Denise is not aware of any memory addresses either. The Paula chip, designed by Glenn Keller, from MOS Technology , is the interrupt controller , but also includes logic for audio playback, floppy disk drive control, serial port input/output and mouse/joystick buttons two and three signals. The logic remained functionally identical across all Amiga models from Commodore. Paula has four DMA -driven 8-bit PCM sound channels. Two sound channels are mixed into
1976-469: Is Direct Memory Access (DMA), where Agnus is the DMA Controller (DMAC). Agnus has a complex and priority-based memory access policy that attempts to best coordinate requests for memory access among competing resources. For example, bitplane data fetches are prioritized over blitter transfers as the immediate display of frame buffer data is considered more important than the processing of memory by
2080-424: Is a form of electronic computer memory that can be read and changed in any order, typically used to store working data and machine code . A random-access memory device allows data items to be read or written in almost the same amount of time irrespective of the physical location of data inside the memory, in contrast with other direct-access data storage media (such as hard disks and magnetic tape ), where
2184-615: Is a type of flip-flop circuit, usually implemented using FETs . This means that SRAM requires very low power when not being accessed, but it is expensive and has low storage density. A second type, DRAM, is based around a capacitor. Charging and discharging this capacitor can store a "1" or a "0" in the cell. However, the charge in this capacitor slowly leaks away, and must be refreshed periodically. Because of this refresh process, DRAM uses more power, but it can achieve greater storage densities and lower unit costs compared to SRAM. To be useful, memory cells must be readable and writable. Within
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#17327917969952288-493: Is achieved by playing the high byte of a 16-bit sample at maximum volume, and the low byte at minimum volume (both ranges overlap, so the low byte needs to be shifted right two bits). The bit shift operation requires a small amount of CPU or blitter overhead, whereas conventional 8-bit playback is almost entirely DMA driven. This technique was incorporated into the retargetable audio subsystem AHI , allowing compatible applications to use this mode transparently. The floppy controller
2392-419: Is arbitrary, thus if 32 colors are not needed, 2, 4, 8 or 16 can be used instead. The number of bitplanes (and resolution) can be changed on the fly, usually by the Copper. This allows for very economical use of RAM, and balancing of CPU processing speed vs graphical sophistication when executing from Chip RAM (as modes beyond 4bpp in lores, or 2bpp in hires, use extra DMA channels that can slow or temporarily halt
2496-530: Is based directly on the NTSC colorburst clock, these sizes very nearly fill the width of a standard television with only a thin "underscan" border between the graphics and the screen border when compared to many other contemporary home computers, for an appearance closer to a games console but with finer detail. On top of this, Denise supports reasonably extensive overscan; technically modes with enough data for up to 400 or 800 pixels (+25%) may be specified, although this
2600-463: Is commonly designated the front-side bus (FSB). Requests to resources not directly controlled by the northbridge were offloaded to the southbridge, with the northbridge being an intermediary between the processor and the southbridge. The southbridge handled "everything else", generally lower-speed peripherals and board functions (the largest being hard disk and storage connectivity) such as USB, parallel and serial communications. In 1990s and early 2000s,
2704-591: Is equivalent to two low resolution (140 ns) pixels or four high resolution (70 ns) pixels. Like Denise, these timings were designed for display on household TVs , and can be synchronized to an external clock source. The blitter is a sub-component of Agnus. "Blit" is shorthand for "block image transfer" or bit blit . The blitter is a highly parallel memory transfer and logic operation unit. It has three modes of operation: copying blocks of memory, filling blocks (e.g. polygon filling) and line drawing. The blitter allows rapid copying of video memory, meaning that
2808-575: Is external to Paula. The filter is a 12 dB/oct Butterworth low-pass filter at approximately 3.3 kHz. The filter can only be applied globally to all four channels. In models after the Amiga ;1000 (excluding the very first revision of the Amiga 500), the brightness of the power LED is used to indicate the status of the filter. The filter is active when the LED is at normal brightness, and deactivated when dimmed (on early Amiga 500 models
2912-403: Is far more expensive than the dynamic RAM used for larger memories. Static RAM also consumes far more power. CPU speed improvements slowed significantly partly due to major physical barriers and partly because current CPU designs have already hit the memory wall in some sense. Intel summarized these causes in a 2005 document. First of all, as chip geometries shrink and clock frequencies rise,
3016-513: Is lost if power is removed. The two main types of volatile random-access semiconductor memory are static random-access memory (SRAM) and dynamic random-access memory (DRAM). Non-volatile RAM has also been developed and other types of non-volatile memories allow random access for read operations, but either do not allow write operations or have other kinds of limitations. These include most types of ROM and NOR flash memory . The use of semiconductor RAM dates back to 1965 when IBM introduced
3120-419: Is more expensive to produce, but is generally faster and requires less dynamic power than DRAM. In modern computers, SRAM is often used as cache memory for the CPU . DRAM stores a bit of data using a transistor and capacitor pair (typically a MOSFET and MOS capacitor , respectively), which together comprise a DRAM cell. The capacitor holds a high or low charge (1 or 0, respectively), and the transistor acts as
3224-606: Is most commonly used to do direct copies (D = A), or apply a pixel mask around blitted objects (D = (C AND B) OR A). The copy can also barrel shift each line by 0 to 15 pixels. This allows the blitter to draw at pixel offsets that are not exactly multiples of 16. These functions allow the Amiga to move GUI windows around the screen rapidly as each is represented in graphical memory space as a rectangular block of memory which may be shifted to any required screen memory location at will. The blitter's line mode draws single-pixel thick lines using Bresenham's line algorithm . It can also apply
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3328-453: Is no explicit "end" instruction; instead, the WAIT instruction is used to wait for a location which is never reached. Under normal circumstances, the Amiga generates its own video timings, but Agnus also supports synchronising the system to an external signal so as to achieve genlocking with external video hardware. There is also a 1-bit output on this connector that indicates whether the Amiga
3432-402: Is on, it sets every pixel until filling mode is turned off or the line ends. Together, these modes allow the blitter to draw individual flat-shaded polygons. Later Amigas tended to use a combination of a faster CPU and blitter for many operations. The Copper is another sub-component of Agnus; The name is short for "co-processor". The Copper is a programmable finite-state machine that executes
3536-440: Is only actually useful for scrolling and special effects that involve partial display of large graphics, as a separate hardware limit is met at 368 (or 736) pixels, which is the maximum that will fit between the end of one blanking period and the start of the next - although it is unlikely that even this many pixels will be visible on any display other than a dedicated monitor that allows adjustment of horizontal scan width, as much of
3640-402: Is outputting background color or not, permitting easy overlaying of Amiga video onto external video. This made the Amiga particularly attractive as a character generator for titling videos and broadcast work, as it avoided the use and expense of A/B roll and chroma key units that would be required without the genlock support. The support of overscan, interlacing and genlocking capabilities, and
3744-489: Is reduced by the size of the shadowed ROMs. The ' memory wall is the growing disparity of speed between CPU and the response time of memory (known as memory latency ) outside the CPU chip. An important reason for this disparity is the limited communication bandwidth beyond chip boundaries, which is also referred to as bandwidth wall . From 1986 to 2000, CPU speed improved at an annual rate of 55% while off-chip memory response time only improved at 10%. Given these trends, it
3848-434: Is rudimentary, using programmed input/output only and lacking a FIFO buffer. However, virtually any bit rate can be selected, including all standard rates, MIDI rate, as well as extremely high custom rates. Chipset In a computer system, a chipset is a set of electronic components on one or more integrated circuits that manages the data flow between the processor , memory and peripherals . The chipset
3952-495: Is the central chip in the design. It controls all access to chip RAM from both the central 68000 processor and the other custom chips, using a complicated priority system. Agnus includes sub-components known as the blitter (fast transfer of data in memory without the intervention of the processor) and the Copper (video-synchronized co-processor). The original Agnus can address 512 KB of chip RAM. Later revisions, dubbed 'Fat Agnus', added 512 KB pseudo-fast RAM, which for ECS
4056-423: Is the processor-memory performance gap, which can be addressed by 3D integrated circuits that reduce the distance between the logic and memory aspects that are further apart in a 2D chip. Memory subsystem design requires a focus on the gap, which is widening over time. The main method of bridging the gap is the use of caches ; small amounts of high-speed memory that houses recent operations and instructions nearby
4160-449: Is unusually flexible. It can read and write raw bit sequences directly from and to the disk via DMA or programmed I/O at 500 ( double density ) or 250 kbit/s ( single density or GCR). MFM or GCR were the two most commonly used formats though in theory any run-length limited code could be used. It also provides a number of convenient features, such as sync-on-word (in MFM coding, $ 4489
4264-433: Is used to control video output, but it can write to most of the chipset registers and thus can be used to initiate blits, set audio registers, or interrupt the CPU. The Copper list has three kinds of instructions, each one being a pair of two bytes, four bytes in total: The length of the Copper list program is limited by execution time. The Copper restarts executing the Copper list at the start of each new video frame. There
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4368-401: Is usually found on the motherboard of computers. Chipsets are usually designed to work with a specific family of microprocessors . Because it controls communications between the processor and external devices, the chipset plays a crucial role in determining system performance . Sometimes the term "chipset" is used to describe a system on chip (SoC) used in a mobile phone. In computing ,
4472-420: Is usually used as the sync word ). MFM encoding/decoding is usually done with the blitter — one pass for decode, three passes for encode. Normally the entire track is read or written in one shot, rather than sector-by-sector; this made it possible to get rid of most of the inter-sector gaps that most floppy disk formats need to safely prevent the "bleeding" of a written sector into the previously-existing header of
4576-578: The Atanasoff–Berry Computer , the Williams tube and the Selectron tube . In 1966, Robert Dennard invented modern DRAM architecture for which there is a single MOS transistor per capacitor. While examining the characteristics of MOS technology, he found it was capable of building capacitors , and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while
4680-504: The Original Amiga chipset and Sega 's System 16 chipset. In x86 -based personal computers, the term chipset often refers to a specific pair of chips on the motherboard: the northbridge and the southbridge . The northbridge links the CPU to very high-speed devices, especially RAM and graphics controllers , and the southbridge connects to lower-speed peripheral buses (such as PCI or ISA ). In many modern chipsets,
4784-604: The floppy disk drive , the serial port , and analog joysticks . There are many similarities – both in overall functionality and in the division of functionality into the three component chips – between the OCS chipset and the much earlier and simpler chipset of the Atari 8-bit computers , consisting of the ANTIC , GTIA and POKEY chips; both chipsets were conceptually designed by Jay Miner , which explains
4888-432: The 1960s with bipolar memory, which used bipolar transistors . Although it was faster, it could not compete with the lower price of magnetic core memory. In 1957, Frosch and Derick manufactured the first silicon dioxide field-effect transistors at Bell Labs, the first transistors in which drain and source were adjacent at the surface. Subsequently, in 1960, a team demonstrated a working MOSFET at Bell Labs. This led to
4992-624: The 1980s, Chips and Technologies pioneered the manufacturing of chipsets for PC-compatible computers. Computer systems produced since then often share commonly used chipsets, even across widely disparate computing specialties. For example, the NCR 53C9x , a low-cost chipset implementing a SCSI interface to storage devices, could be found in Unix machines such as the MIPS Magnum , embedded devices, and personal computers. Traditionally in x86 computers,
5096-680: The Amiga its unique graphics features consists of three main "custom" chips: Agnus , Denise , and Paula . Both the original chipset and the enhanced chipset were manufactured using NMOS logic technology by Commodore 's chip manufacturing subsidiary, MOS Technology . According to Jay Miner , the OCS chipset was fabricated in 5 μm manufacturing process while AGA Lisa was implemented in 1.5 μm process. All three custom chips were originally packaged in 48-pin DIPs ; later versions of Agnus, known as Fat Agnus, were packaged in an 84-pin PLCC . Agnus
5200-505: The BIOS's ROM instead use DRAM locations (most can also toggle shadowing of video card ROM or other ROM sections). Depending on the system, this may not result in increased performance, and may cause incompatibilities. For example, some hardware may be inaccessible to the operating system if shadow RAM is used. On some systems the benefit may be hypothetical because the BIOS is not used after booting in favor of direct hardware access. Free memory
5304-544: The Baby, the Baby was a testbed to demonstrate the reliability of the memory. Magnetic-core memory was invented in 1947 and developed up until the mid-1970s. It became a widespread form of random-access memory, relying on an array of magnetized rings. By changing the sense of each ring's magnetization, data could be stored with one bit stored per ring. Since every ring had a combination of address wires to select and read or write it, access to any memory location in any sequence
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#17327917969955408-444: The CPU can be freed for other tasks. The blitter was primarily used for drawing and redrawing graphics images on the screen, called "bobs", short for "blitter objects". The blitter's block copying mode takes zero to three data sources in memory, called A, B and C, performs a programmable Boolean function on the data sources and writes the result to a destination area, D. Any of these four areas can overlap. The blitter runs either from
5512-584: The CPU die itself (the chipset often contains secondary PCIe connections though). However, the Platform Controller Hub was also integrated into the processor package as a second die for mobile variants of the Skylake processors. AMD's FCH has been discontinued since the release of the Carrizo series of CPUs as it has been integrated into the same die as the rest of the CPU. However, since
5616-410: The CPU does not generally get locked out of memory access and does not appear to slow down. However, non-time-critical custom chip access, such as blitter transfers, can use up any spare odd or even cycles and, if the "BLITHOG" (blitter hog) flag is set, Agnus can lock out the even cycles from the CPU in deference to the blitter . Agnus's timings are measured in "color clocks" of 280 ns . This
5720-405: The CPU in addition to the usual non-conflicting channels). There can also be a sixth bitplane, which can be used in three special graphics modes: There are two horizontal graphics resolutions, "lowres" with 140 ns pixels and "hires" with 70 ns pixels, with a default of 320 or 640 horizontal pixels wide without using overscan. As the pixel output is regulated by the main system clock, which
5824-506: The DMA slots dedicated to playfield video ends up stealing some (from 1 to 7 of the total 8) the sprite engine. [1] . Vertical resolution, without overscan, is 200 pixels for a 60 Hz NTSC Amiga or 256 for a 50 Hz PAL Amiga. This can be doubled using an interlaced display, and, as with horizontal resolution, increased using overscan, to a maximum of 241 (or 483) for NTSC, and 283 (or 567) for PAL (interlaced modes gaining one extra line as
5928-464: The LED went completely off). Models released before Amiga 1200 also have a static "tone knob" type low-pass filter that is enabled regardless of the optional "LED filter". This filter is a 6 dB/oct low-pass filter with cutoff frequency at 4.5 or 5 kHz. A software technique was later developed which can play back 14-bit audio by combining two channels set at different volumes. This results in two 14-bit channels instead of four 8-bit channels. This
6032-453: The MOS transistor could control writing the charge to the capacitor. This led to his development of a single-transistor DRAM memory cell. In 1967, Dennard filed a patent under IBM for a single-transistor DRAM memory cell, based on MOS technology. The first commercial DRAM IC chip was the Intel 1103 , which was manufactured on an 8 μm MOS process with a capacity of 1 kbit , and
6136-441: The RAM comes in an easily upgraded form of modules called memory modules or DRAM modules about the size of a few sticks of chewing gum. These can be quickly replaced should they become damaged or when changing needs demand more storage capacity. As suggested above, smaller amounts of RAM (mostly SRAM) are also integrated in the CPU and other ICs on the motherboard , as well as in hard-drives, CD-ROMs , and several other parts of
6240-444: The RAM device, multiplexing and demultiplexing circuitry is used to select memory cells. Typically, a RAM device has a set of address lines A 0 , A 1 , . . . A n {\displaystyle A_{0},A_{1},...A_{n}} , and for each combination of bits that may be applied to these lines, a set of memory cells are activated. Due to this addressing, RAM devices virtually always have
6344-587: The SP95 memory chip for the System/360 Model 95 . Dynamic random-access memory (DRAM) allowed replacement of a 4 or 6-transistor latch circuit by a single transistor for each memory bit, greatly increasing memory density at the cost of volatility. Data was stored in the tiny capacitance of each transistor, and had to be periodically refreshed every few milliseconds before the charge could leak away. Toshiba 's Toscal BC-1411 electronic calculator , which
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#17327917969956448-459: The blitter. Agnus also attempts to order accesses in such a way so as to overlap CPU bus cycles with DMA cycles. As the original 68000 processor in Amigas tended only to access memory on every second available memory cycle, Agnus operates a system where "odd" memory access cycles are allocated first and as needed to time-critical custom chip DMA while any remaining cycles are available to the CPU, thus
6552-405: The computer system. In addition to serving as temporary storage and working space for the operating system and applications, RAM is used in numerous other ways. Most modern operating systems employ a method of extending RAM capacity, known as "virtual memory". A portion of the computer's hard drive is set aside for a paging file or a scratch partition , and the combination of physical RAM and
6656-448: The development of metal–oxide–semiconductor (MOS) memory by John Schmidt at Fairchild Semiconductor in 1964. In addition to higher speeds, MOS semiconductor memory was cheaper and consumed less power than magnetic core memory. The development of silicon-gate MOS integrated circuit (MOS IC) technology by Federico Faggin at Fairchild in 1968 enabled the production of MOS memory chips . MOS memory overtook magnetic core memory as
6760-408: The device are used to activate the correct device that is being accessed. RAM is often byte addressable, although it is also possible to make RAM that is word-addressable. One can read and over-write data in RAM. Many computer systems have a memory hierarchy consisting of processor registers , on- die SRAM caches, external caches , DRAM , paging systems and virtual memory or swap space on
6864-460: The discussion of Agnus, memory access is prioritized and one DMA slot per scan line is available for each of the four sound channels. On a regular NTSC or PAL display, DMA audio playback is limited to a maximum output rate of 28,867 values per channel (PAL: 28837) per second totaling 57674 (PAL: 57734) values per second on each stereo output. This rate can be increased with the ECS and AGA chipsets by using
6968-437: The dominant memory technology in the early 1970s. Integrated bipolar static random-access memory (SRAM) was invented by Robert H. Norman at Fairchild Semiconductor in 1963. It was followed by the development of MOS SRAM by John Schmidt at Fairchild in 1964. SRAM became an alternative to magnetic-core memory, but required six MOS transistors for each bit of data. Commercial use of SRAM began in 1965, when IBM introduced
7072-410: The extent that access time to rotating storage media or a tape is variable. The overall goal of using a memory hierarchy is to obtain the fastest possible average access time while minimizing the total cost of the entire memory system (generally, the memory hierarchy follows the access time with the fast CPU registers at the top and the slow hard drive at the bottom). In many modern personal computers,
7176-430: The fact that the display timing was very close to broadcast standards (NTSC or PAL), made the Amiga the first ideal computer for video purposes, and indeed, it was used in many studios for digitizing video data (sometimes called frame-grabbing), subtitling and interactive video news. Denise is programmed to fetch planar video data from one to five bitplanes and translate that into a color lookup . The number of bitplanes
7280-412: The fundamental building block of computer memory . The memory cell is an electronic circuit that stores one bit of binary information and it must be set to store a logic 1 (high voltage level) and reset to store a logic 0 (low voltage level). Its value is maintained/stored until it is changed by the set/reset process. The value in the memory cell can be accessed by reading it. In SRAM, the memory cell
7384-414: The hardware allows one channel in a channel pair to modulate the other channel's period or amplitude. It is rarely used on the Amiga due to both frequency and volume being controllable in better ways, but could be used to achieve different kinds of tremolo and vibrato , and even rudimentary FM synthesis effects. Audio may be output using two methods. Most often, DMA-driven audio is used. As explained in
7488-434: The image will, by design, disappear seamlessly behind the screen bezel (or, on LCDs, be cropped off at the edge of the panel). Because of the highly regular structure of the Amiga's timing in relation to scanlines and allocation of DMA resources to various uses besides normal "playfield" graphics, increased horizontal resolution is also a tradeoff between number of pixels and how many hardware sprites are available, as increasing
7592-446: The individual bits per pixel into separate areas of memory, called bitplanes . In normal operation, Denise allows between one and five bitplanes, giving two to 32 unique colors. These colors are selected from a palette of 4096 colors (four bits per RGB component). A 6th bitplane is available for two special video modes: Halfbrite mode and Hold-And-Modify (HAM) mode. Denise also supports eight sprites , single pixel scrolling, and
7696-696: The integration of PCI bridge logic, the GraphiCore 2D graphics accelerator and direct support for synchronous DRAM, the forerunner of DDR SDRAM memory. The Apple Macintosh SE , Macintosh II and later the Quadras series used chipsets from VLSI Technology , even though they were ASICs designed by Apple. After the switch to PowerPC , Apple used various ASIC suppliers for their chipsets such as VLSI technology, Texas Instruments , LSI Logic or Lucent Technologies (later known as Agere Systems ). When Apple switched to Intel they used traditional PC chipsets. In
7800-454: The interface between a northbridge and southbridge was the PCI bus. Before 2003, any interaction between a CPU and main memory or an expansion device such as a graphics card(s) — whether AGP , PCI or integrated into the motherboard — was directly controlled by the northbridge IC on behalf of the processor. This made processor performance highly dependent on the system chipset, especially
7904-400: The left audio output, and the other two are mixed into the right output, producing stereo audio output. The only supported hardware sample format is signed linear 8-bit two's complement . Each sound channel has an independent frequency and a 6-bit volume control (64 levels). Internally, the audio hardware is implemented by four state machines, each having eight different states. Additionally
8008-449: The less-than-ideal file system of the earlier Amiga models reduced this again to approximately 830 KB of actual payload data. In addition to the native 880 KB 3.5-inch disk format, the controller can handle many foreign formats, such as: The Amiga 3000 introduced a special, dual-speed floppy drive that also allowed use of high density disks with double capacity without any change to Paula's floppy controller. The serial port
8112-552: The maximum is determined by how many lines are taken from the available total by blanking and sync, and the total scanlines in non-interlaced modes are half the original, broadcast-spec odd-numbered interlaced counts, rounded down). Starting with ECS, Denise was upgraded to support "Productivity" mode which allowed for 640x400 non-interlaced albeit with only 4 colors. Denise can composite up to eight 16-pixel-wide sprites per scan line (in automatic mode) on top, underneath, or between playfields, and detect collisions between sprites and
8216-545: The means of producing inductance within solid state devices, resistance-capacitance (RC) delays in signal transmission are growing as feature sizes shrink, imposing an additional bottleneck that frequency increases don't address. The RC delays in signal transmission were also noted in "Clock Rate versus IPC: The End of the Road for Conventional Microarchitectures" which projected a maximum of 12.5% average annual CPU performance improvement between 2000 and 2014. A different concept
8320-436: The memory cannot be altered. Writable variants of ROM (such as EEPROM and NOR flash ) share properties of both ROM and RAM, enabling data to persist without power and to be updated without requiring special equipment. ECC memory (which can be either SRAM or DRAM) includes special circuitry to detect and/or correct random faults (memory errors) in the stored data, using parity bits or error correction codes . In general,
8424-467: The monolithic (single-chip) 16-bit SP95 SRAM chip for their System/360 Model 95 computer, and Toshiba used bipolar DRAM memory cells for its 180-bit Toscal BC-1411 electronic calculator , both based on bipolar transistors . While it offered higher speeds than magnetic-core memory , bipolar DRAM could not compete with the lower price of the then-dominant magnetic-core memory. In 1966, Dr. Robert Dennard invented modern DRAM architecture in which there's
8528-430: The next sector due to speed variations of the drive. If all sectors and their headers are always written in one go, such bleeding is only an issue at the end of the track (which still must not bleed back into its beginning), so that only one gap per track is needed. This way, for the native Amiga disk format, the raw storage capacity of 3.5 inch DD disks was increased from the typical 720 KB to 880 KB, although
8632-454: The northbridge's memory performance and ability to shuttle this information back to the processor. In 2003, however, AMD's introduction of the Athlon 64 series of processors changed this. The Athlon 64 marked the introduction of an integrated memory controller being incorporated into the processor itself thus allowing the processor to directly access and handle memory, negating the need for
8736-443: The order it was written. Drum memory could be expanded at relatively low cost but efficient retrieval of memory items requires knowledge of the physical layout of the drum to optimize speed. Latches built out of triode vacuum tubes , and later, out of discrete transistors , were used for smaller and faster memories such as registers . Such registers were relatively large and too costly to use for large amounts of data; generally only
8840-571: The paging file form the system's total memory. (For example, if a computer has 2 GB (1024 B) of RAM and a 1 GB page file, the operating system has 3 GB total memory available to it.) When the system runs low on physical memory, it can " swap " portions of RAM to the paging file to make room for new data, as well as to read previously swapped information back into RAM. Excessive use of this mechanism results in thrashing and generally hampers overall system performance, mainly because hard drives are far slower than RAM. Software can "partition"
8944-521: The playfields or between sprites. These sprites have three visible colors and one transparent color. Optionally, adjacent pairs of sprites can be "attached" to make a single 15-color sprite. The Sprite DMA reads data to form a sprite channel as controlled by its registers, enabling the vertical reuse of sprites. There has to be one empty scanline in between two successive list entries to allow for updating sprite data. Using Copper or CPU register manipulations, each sprite channel can be reused multiple times in
9048-414: The processor's primary connection to the rest of the machine was through the motherboard chipset's northbridge. The northbridge was directly responsible for communications with high-speed devices (system memory and primary expansion buses, such as PCIe, AGP, and PCI cards, being common examples) and conversely any system communication back to the processor. This connection between the processor and northbridge
9152-577: The processor, speeding up the execution of those operations or instructions in cases where they are called upon frequently. Multiple levels of caching have been developed to deal with the widening gap, and the performance of high-speed modern computers relies on evolving caching techniques. There can be up to a 53% difference between the growth in speed of processor and the lagging speed of main memory access. Solid-state hard drives have continued to increase in speed, from ~400 Mbit/s via SATA3 in 2012 up to ~7 GB/s via NVMe / PCIe in 2024, closing
9256-521: The release of the Zen architecture, there's still a component called a chipset which only handles relatively low speed I/O such as USB and SATA ports and connects to the CPU with a PCIe connection. In these systems all PCIe connections are routed directly to the CPU. The UMI interface previously used by AMD for communicating with the FCH is replaced with a PCIe connection. Technically the processor can operate without
9360-445: The remaining northbridge and southbridge functions into a single chip. Intel's version of this is the " Platform Controller Hub " (PCH) while AMD's version was called Fusion Controller Hub (FCH). The PCH is still called a chipset. This is an enhanced southbridge for the remaining peripherals—as traditional northbridge duties, such as memory controller, expansion bus (PCIe) interface and even on-board video controller, are integrated into
9464-435: The same type, simply because it takes longer for signals to traverse a larger circuit. Constructing a memory unit of many gibibytes with a response time of one clock cycle is difficult or impossible. Today's CPUs often still have a mebibyte of 0 wait state cache memory, but it resides on the same chip as the CPU cores due to the bandwidth limitations of chip-to-chip communication. It must also be constructed from static RAM, which
9568-466: The similarity. The Agnus chip is in overall control of the entire chipset's operation. All operations are synchronised to the position of the video beam. This includes access to the built-in RAM , known as chip RAM because the chipset has access to it. Both the central 68000 processor and other members of the chipset have to arbitrate for access to chip RAM via Agnus . In computing architecture terms, this
9672-496: The southbridge contains some on-chip integrated peripherals , such as Ethernet , USB , and audio devices. Motherboards and their chipsets often come from different manufacturers. As of 2021 , manufacturers of chipsets for x86 motherboards include AMD , Intel , VIA Technologies and Zhaoxin . In the 1990s, a major designer and manufacturer of chipsets was VLSI Technology in Tempe, Arizona. Some of their innovations included
9776-482: The start of the block to the end, known as "ascending" mode, or in reverse, "descending" mode. Blocks are "rectangular"; they have a "width" in multiples of 16 bits, a height measured in "lines", and a "stride" distance to move from the end of one line to the next. This allows the blitter to operate on any video resolution up to 1,024×1,024 pixels. The copy automatically performs a per-pixel logical operation. These operations are described generically using minterms . This
9880-400: The term RAM refers solely to solid-state memory devices (either DRAM or SRAM), and more specifically the main memory in most computers. In optical storage, the term DVD-RAM is somewhat of a misnomer since, it is not random access; it behaves much like a hard disc drive if somewhat slower. Aside, unlike CD-RW or DVD-RW , DVD-RAM does not need to be erased before reuse. The memory cell is
9984-559: The term chipset commonly refers to a set of specialized chips on a computer 's motherboard or an expansion card . In personal computers , the first chipset for the IBM PC AT of 1984 was the NEAT chipset developed by Chips and Technologies for the Intel 80286 CPU. In home computers , game consoles, and arcade hardware of the 1980s and 1990s, the term chipset was used for the custom audio and graphics chips. Examples include
10088-443: The time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement. In today's technology, random-access memory takes the form of integrated circuit (IC) chips with MOS (metal–oxide–semiconductor) memory cells . RAM is normally associated with volatile types of memory where stored information
10192-558: The transistor leakage current increases, leading to excess power consumption and heat... Secondly, the advantages of higher clock speeds are in part negated by memory latency, since memory access times have not been able to keep pace with increasing clock frequencies. Third, for certain applications, traditional serial architectures are becoming less efficient as processors get faster (due to the so-called von Neumann bottleneck ), further undercutting any gains that frequency increases might otherwise buy. In addition, partly due to limitations in
10296-498: Was Samsung's 64 Mbit DDR SDRAM chip, released in June 1998. GDDR (graphics DDR) is a form of DDR SGRAM (synchronous graphics RAM), which was first released by Samsung as a 16 Mbit memory chip in 1998. The two widely used forms of modern RAM are static RAM (SRAM) and dynamic RAM (DRAM). In SRAM, a bit of data is stored using the state of a six- transistor memory cell , typically using six MOSFETs. This form of RAM
10400-459: Was changed to 1 MB (sometimes called 'Fatter Agnus') and subsequently to 2 MB chip RAM. Denise is the main video processor. Without using overscan , the Amiga's graphics display is 320 or 640 pixels wide by 200 ( NTSC ) or 256 ( PAL ) pixels tall. Denise also supports interlacing , which doubles the vertical resolution, at the cost of intrusive flickering on typical monitors of that era. Planar bitmap graphics are used, which splits
10504-493: Was expected that memory latency would become an overwhelming bottleneck in computer performance. Another reason for the disparity is the enormous increase in the size of memory since the start of the PC revolution in the 1980s. Originally, PCs contained less than 1 mebibyte of RAM, which often had a response time of 1 CPU clock cycle, meaning that it required 0 wait states. Larger memory units are inherently slower than smaller ones of
10608-410: Was introduced in 1965, used a form of capacitor-bipolar DRAM, storing 180-bit data on discrete memory cells , consisting of germanium bipolar transistors and capacitors. While it offered higher speeds than magnetic-core memory, bipolar DRAM could not compete with the lower price of the then dominant magnetic-core memory. Capacitors had also been used for earlier memory schemes, such as the drum of
10712-460: Was possible. Magnetic core memory was the standard form of computer memory until displaced by semiconductor memory in integrated circuits (ICs) during the early 1970s. Prior to the development of integrated read-only memory (ROM) circuits, permanent (or read-only ) random-access memory was often constructed using diode matrices driven by address decoders , or specially wound core rope memory planes. Semiconductor memory appeared in
10816-433: Was released in 1970. The earliest DRAMs were often synchronized with the CPU clock (clocked) and were used with early microprocessors. In the mid-1970s, DRAMs moved to the asynchronous design, but in the 1990s returned to synchronous operation. In 1992 Samsung released KM48SL2000, which had a capacity of 16 Mbit . and mass-produced in 1993. The first commercial DDR SDRAM ( double data rate SDRAM) memory chip
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