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58-589: Originally referred to as the PC bus (8-bit) or AT bus (16-bit), it was also termed I/O Channel by IBM. The ISA term was coined as a retronym by IBM PC clone manufacturers in the late 1980s or early 1990s as a reaction to IBM attempts to replace the AT bus with its new and incompatible Micro Channel architecture . The 16-bit ISA bus was also used with 32-bit processors for several years. An attempt to extend it to 32 bits, called Extended Industry Standard Architecture (EISA),

116-724: A 16-bit transfer size, signal timing in the PIO modes and the interrupt and DMA mechanisms. The PC/XT-bus is an eight- bit ISA bus used by Intel 8086 and Intel 8088 systems in the IBM PC and IBM PC XT in the 1980s. Among its 62 pins were demultiplexed and electrically buffered versions of the 8 data and 20 address lines of the 8088 processor, along with power lines, clocks, read/write strobes, interrupt lines, etc. Power lines included −5 V and ±12 V in order to directly support pMOS and enhancement mode nMOS circuits such as dynamic RAMs among other things. The XT bus architecture uses

174-593: A VL-Bus slot. In the early 1990s, the I/O bandwidth of the prevailing ISA bus, 8.33 MB/s for standard 16 bit 8.33 MHz slots, had become a critical bottleneck to PC video and graphics performance. The need for faster graphics was driven by increased adoption of graphical user interfaces in PC operating systems. While IBM did produce a viable successor to ISA with the Micro Channel Architecture offering

232-508: A bandwidth of 66 MB/s, it failed in the market because hardware manufacturers did not want to pay steep licensing fees to use it. While an extension of the royalty-free ISA bus in the form of EISA open standard was developed to counter MCA, its bandwidth of 33.32 MB/s was unable to offer enough improvement over ISA to meet the significant increase in bandwidth desired for graphics. It would be superseded by Peripheral Component Interconnect (PCI), starting at speeds of 133 MB/s (32-bit at 33 MHz in

290-420: A card directly to the 486 processor bus with minimal intermediary logic (reducing logic design and component costs), timing and arbitration duties were strongly dependent on the cards and CPU. This simplicity of VLB unfortunately created several factors that served to limit its useful life substantially: As VLB devices have direct high-speed access to system memory at the same level as the main processor, there

348-524: A few unique signal lines specific to ATA/IDE hard disks (such as the Cable Select/Spindle Sync. line.) In addition to the physical interface channel, ATA goes beyond and far outside the scope of ISA by also specifying a set of physical device registers to be implemented on every ATA (IDE) drive and a full set of protocols and device commands for controlling fixed disk drives using these registers. The ATA device registers are accessed using

406-405: A second 8259 PIC (connected to one of the lines of the first) and 4 × 16-bit DMA channels, as well as control lines to select 8- or 16-bit transfers. The 16-bit AT bus slot originally used two standard edge connector sockets in early IBM PC/AT machines. However, with the popularity of the AT architecture and the 16-bit ISA bus, manufacturers introduced specialized 98-pin connectors that integrated

464-578: A separate clock generator, or a clock divider which either fixed the ISA bus frequency at 4, 6, or 8 MHz or allowed the user to adjust the frequency via the BIOS setup. When used at a higher bus frequency, some ISA cards (certain Hercules-compatible video cards, for instance), could show significant performance improvements. Memory address decoding for the selection of 8 or 16-bit transfer mode

522-602: A single Intel 8259 PIC , giving eight vectorized and prioritized interrupt lines. It has four DMA channels originally provided by the Intel 8237 . Three of the DMA channels are brought out to the XT bus expansion slots; of these, 2 are normally already allocated to machine functions (diskette drive and hard disk controller): The PC/AT-bus , a 16- bit (or 80286-) version of the PC/XT bus,

580-495: A slower but more compatible bus speed (33 MHz) and a multiplier (×2) to derive the processor clock speed. Due to the length of a VLB slot and the difficult installation that results from its length, a slang alternative use of the acronym VLB is Very Long Bus . Despite these problems, the VESA Local Bus became very commonplace on later 486 motherboards, with a majority of later (post-1992) 486-based systems featuring

638-603: A time, but this allowed for greater flexibility. The AT Attachment (ATA) hard disk interface is directly descended from the 16-bit ISA of the PC/AT. ATA has its origins in the IBM Personal Computer Fixed Disk and Diskette Adapter, the standard dual-function floppy disk controller and hard disk controller card for the IBM PC AT; the fixed disk controller on this card implemented the register set and

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696-454: Is a derivative of the ISA bus, utilizing the same signal lines with different connectors. The LPC bus has replaced the ISA bus as the connection to the legacy I/O devices on current motherboards; while physically quite different, LPC looks just like ISA to software, so the peculiarities of ISA such as the 16 MiB DMA limit (which corresponds to the full address space of the Intel 80286 CPU used in

754-527: Is equipped with two ISA slots. It was marketed to industrial and military users who had invested in expensive specialized ISA bus adaptors, which were not available in PCI bus versions. Similarly, ADEK Industrial Computers released a modern motherboard in early 2013 for Intel Core i3/i5/i7 processors, which contains one (non-DMA) ISA slot. Also, MSI released a modern motherboard with one ISA slot in 2020. The PC/104 bus, used in industrial and embedded applications,

812-514: Is newer, similar, or seen in everyday life; thus, avoiding confusion between the two. The term retronym , a neologism composed of the combining forms retro- (from Latin retro , "before") + -nym (from Greek ónoma , "name"), was coined by Frank Mankiewicz in 1980 and popularized by William Safire in The New York Times Magazine . In 2000, The American Heritage Dictionary (4th edition) became

870-468: Is no way for the system to intervene if devices were mis-configured or became unstable. If two devices overwrite the same memory location in a conflict, and the hard-disk controller relies on this location (the HDD controller often being the second conflicting device), there is the all-too-common possibility of massive data corruption . The 486DX-50's successor, the 486DX2-66, circumvents this problem by using

928-414: Is now fairly hard to find. Some XT-IDE adapters were available as 8-bit ISA cards, and XTA sockets were also present on the motherboards of Amstrad 's later XT clones as well as a short-lived line of Philips units. The XTA pinout was very similar to ATA, but only eight data lines and two address lines were used, and the physical device registers had completely different meanings. A few hard drives (such as

986-496: The Extended Industry Standard Architecture (EISA) and the later VESA Local Bus (VLB). VLB used some electronic parts originally intended for MCA because component manufacturers already were equipped to manufacture them. Both EISA and VLB were backward-compatible expansions of the AT (ISA) bus. Users of ISA-based machines had to know special information about the hardware they were adding to

1044-467: The Seagate ST351A/X) could support either type of interface, selected with a jumper. Many later AT (and AT successor) motherboards had no integrated hard drive interface but relied on a separate hard drive interface plugged into an ISA/EISA/VLB slot. There were even a few 80486-based units shipped with MFM/RLL interfaces and drives instead of the increasingly common AT-IDE. Commodore built

1102-523: The 8-bit version as a buffered interface to the motherboard buses of the Intel 8088 (16/8 bit) CPU in the IBM PC and PC/XT, augmented with prioritized interrupts and DMA channels. The 16-bit version was an upgrade for the motherboard buses of the Intel 80286 CPU (and expanded interrupt and DMA facilities) used in the IBM AT, with improved support for bus mastering. The ISA bus was therefore synchronous with

1160-575: The AT bus's performance but in 1987, IBM replaced the AT bus with its proprietary Micro Channel Architecture (MCA). MCA overcame many of the limitations then apparent in ISA but was also an effort by IBM to regain control of the PC architecture and the PC market. MCA was far more advanced than ISA and had many features that would later appear in PCI. However, MCA was also a closed standard whereas IBM had released full specifications and circuit schematics for ISA. Computer manufacturers responded to MCA by developing

1218-451: The ATA standard (up to 133 MB/s for ATA-6, the latest.) In most forms, ATA ran much faster than ISA, provided it was connected directly to a local bus (e.g. southbridge-integrated IDE interfaces) faster than the ISA bus. Before the 16-bit ATA/IDE interface, there was an 8-bit XT-IDE (also known as XTA) interface for hard disks. It was not nearly as popular as ATA has become, and XT-IDE hardware

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1276-516: The CPU clock of the 80286 in IBM PC/AT computers, which was 6 MHz in the first models and 8 MHz in later models. The IBM RT PC also used the 16-bit bus. ISA was also used in some non-IBM compatible machines such as Motorola 68k -based Apollo (68020) and Amiga 3000 (68030) workstations, the short-lived AT&T Hobbit and the later PowerPC -based BeBox . Companies like Dell improved

1334-402: The CPU clock until sophisticated buffering methods were implemented by chipsets to interface ISA to much faster CPUs. ISA was designed to connect peripheral cards to the motherboard and allows for bus mastering . Only the first 16 MB of main memory is addressable. The original 8-bit bus ran from the 4.77 MHz clock of the 8088 CPU in the IBM PC and PC/XT. The original 16-bit bus ran from

1392-533: The CPU's bus speed: It started at 100 MB/s for CPUs with a 25 MHz bus, increased to 133 MB/s at 33 MHz and 160 MB/s at 40 MHz, and reached 200 MB/s at 50 MHz. A "VLB slot" itself is an additional edge connector placed in-line with the traditional ISA or EISA connector, with this extended portion often colored a distinctive brown. The result is a normal ISA or EISA slot being additionally capable of accepting VLB-compatible cards. Traditional ISA cards remain compatible, as they do not have pins past

1450-515: The P996 specification. However, despite books being published on the P996 specification, it never officially progressed past draft status. There still is an existing user base with old computers, so some ISA cards are still manufactured, e.g. with USB ports or complete single-board computers based on modern processors, USB 3.0 , and SATA . Retronym A retronym is a newer name for something that differentiates it from something else that

1508-514: The PC bus—the AT bus connector was a superset of the PC bus connector. In 1988, the 32-bit EISA standard was proposed by the "Gang of Nine" group of PC-compatible manufacturers that included Compaq. Compaq created the term Industry Standard Architecture (ISA) to replace PC compatible . In the process, they retroactively renamed the AT bus to ISA to avoid infringing IBM's trademark on its PC and PC/AT systems (and to avoid giving their major competitor, IBM, free advertisement). IBM designed

1566-476: The PCMCIA interface is much more complex than ATA. Although most modern computers do not have physical ISA buses, almost all PCs — IA-32 , and x86-64 — have ISA buses allocated in physical address space. Some Southbridges and some CPUs themselves provide services such as temperature monitoring and voltage readings through ISA buses as ISA devices. IEEE started a standardization of the ISA bus in 1985, called

1624-460: The VESA Local Bus worked alongside the then-dominant ISA bus to provide a standardized high-speed conduit intended primarily to accelerate video (graphics) operations. VLB provides a standardized fast path that add-in (video) card makers could tap for greatly accelerated memory-mapped I/O and DMA , while still using the familiar ISA bus to handle basic device duties such as interrupts and port-mapped I/O . Some high-end 386DX motherboards also had

1682-578: The XT-IDE-based peripheral hard drive and memory expansion unit A590 for their Amiga 500 and 500+ computers that also supported a SCSI drive. Later models – the A600 , A1200 , and the Amiga 4000 series – use AT-IDE drives. The PCMCIA specification can be seen as a superset of ATA. The standard for PCMCIA hard disk interfaces, which included PCMCIA flash drives, allows for the mutual configuration of

1740-734: The address bits and address select signals in the ATA physical interface channel, and all operations of ATA hard disks are performed using the ATA-specified protocols through the ATA command set. The earliest versions of the ATA standard featured a few simple protocols and a basic command set comparable to the command sets of MFM and RLL controllers (which preceded ATA controllers), but the latest ATA standards have much more complex protocols and instruction sets that include optional commands and protocols providing such advanced optional-use features as sizable hidden system storage areas, password security locking, and programmable geometry translation. In

1798-504: The attention of the VESA consortium and resulted in a proposal for a voluntary and royalty-free local bus standard in 1992. An additional benefit from this standardization (beyond the primary goal of greater graphics card performance) was that other devices could also be designed to utilize the performance offered from VLB; notably, mass-storage controllers were offered for VLB, providing increased hard-disk performance. VLB bandwidth depended on

Industry Standard Architecture - Misplaced Pages Continue

1856-575: The basic command set which became the basis of the ATA interface (and which differed greatly from the interface of IBM's fixed disk controller card for the PC XT). Direct precursors to ATA were third-party ISA hardcards that integrated a hard disk drive (HDD) and a hard disk controller (HDC) onto one card. This was at best awkward and at worst damaging to the motherboard, as ISA slots were not designed to support such heavy devices as HDDs. The next generation of Integrated Drive Electronics drives moved both

1914-443: The coinage of retronyms. For example, the term acoustic guitar was coined with the advent of the electric guitar , analog watch was introduced to distinguish from the digital watch , push bike was created to distinguish from the motorized bicycle , and feature phone was coined to distinguish from the smartphone . Likewise, visible light refers to electromagnetic radiation on the narrow visible spectrum , and water ice

1972-438: The creation of ISA PnP , a plug-n-play system that used a combination of modifications to hardware, the system BIOS , and operating system software to automatically manage resource allocations. In reality, ISA PnP could be troublesome and did not become well-supported until the architecture was in its final days. A PnP ISA, EISA or VLB device may have a 5-byte EISA ID (3-byte manufacturer ID + 2-byte hex number) to identify

2030-479: The device. For example, CTL0044 corresponds to Creative Sound Blaster 16 / 32 PnP . PCI slots were the first physically incompatible expansion ports to directly squeeze ISA off the motherboard. At first, motherboards were largely ISA, including a few PCI slots. By the mid-1990s, the two slot types were roughly balanced, and ISA slots soon were in the minority of consumer systems. Microsoft 's PC-99 specification recommended that ISA slots be removed entirely, though

2088-574: The drive and controller to a drive bay and used a ribbon cable and a very simple interface board to connect it to an ISA slot. ATA is basically a standardization of this arrangement plus a uniform command structure for software to interface with the HDC within the drive. ATA has since been separated from the ISA bus and connected directly to the local bus, usually by integration into the chipset, for much higher clock rates and data throughput than ISA could support. ATA has clear characteristics of 16-bit ISA, such as

2146-468: The end. In late 2008, even floppy disk drives and serial ports were disappearing, and the extinction of vestigial ISA (by then the LPC bus) from chipsets was on the horizon. PCI slots are rotated compared to their ISA counterparts—PCI cards were essentially inserted upside-down, allowing ISA and PCI connectors to squeeze together on the motherboard. Only one of the two connectors can be used in each slot at

2204-510: The first major dictionary to include the word retronym . The global war from 1914 to 1918 was referred to at the time as the Great War . However, after the subsequent global war erupted in 1939, the phrase Great War was gradually deprecated. The first came to be known as World War I and the second as World War II . The first bicycles with two wheels of equal size were called " safety bicycles " because they were easier to handle than

2262-632: The launch of its successor, the Atari 5200 , and all hardware and software related to the platform were released under this new branding from that point on. Prior to that time, Atari often used the initialism "VCS" in official literature and other media, but colloquially the Video Computer System was often simply called "the Atari." The first film in the Star Wars franchise released in 1977

2320-448: The mid-1990s, the ATA host controller (usually integrated into the chipset) was moved to PCI form. A further deviation between ISA and ATA is that while the ISA bus remained locked into a single standard clock rate (for backward hardware compatibility), the ATA interface offered many different speed modes, could select among them to match the maximum speed supported by the attached drives, and kept adding faster speeds with later versions of

2378-526: The normal ISA or EISA portion of the slot. The reverse was also true – VLB cards are by necessity quite long in order to reach the VLB connector and were reminiscent of older full-length expansion cards from the earlier IBM XT era. The VLB portion of a slot looks similar to an IBM MCA slot, as indeed it is the same physical 116-pin connector used by MCA cards, rotated by 180 degrees. The IBM MCA standard had not been as popular as IBM expected, and there

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2436-583: The original IBM AT) are likely to stick around for a while. As explained in the History section, ISA was the basis for development of the ATA interface, used for ATA (a.k.a. IDE) hard disks. Physically, ATA is essentially a simple subset of ISA, with 16 data bits, support for exactly one IRQ and one DMA channel, and 3 address bits. To this ISA subset, ATA adds two IDE address select ("chip select") lines (i.e. address decodes, effectively equivalent to address bits) and

2494-496: The port and the drive in an ATA mode. As a de facto extension, most PCMCIA flash drives additionally allow for a simple ATA mode that is enabled by pulling a single pin low, so that PCMCIA hardware and firmware are unnecessary to use them as an ATA drive connected to an ATA port. PCMCIA flash drive to ATA adapters are thus simple and inexpensive but are not guaranteed to work with any and every standard PCMCIA flash drive. Further, such adapters cannot be used as generic PCMCIA ports, as

2552-487: The same time, up to 4 devices may use one 8-bit DMA channel each, while up to 3 devices can use one 16-bit DMA channel each. Originally, the bus clock was synchronous with the CPU clock, resulting in varying bus clock frequencies among the many different IBM clones on the market (sometimes as high as 16 or 20 MHz), leading to software or electrical timing problems for certain ISA cards at bus speeds they were not designed for. Later motherboards or integrated chipsets used

2610-466: The standard configuration) Thus for a short time, a market opening occurred where video card manufacturers and motherboard chipset makers created their own proprietary implementations of local buses to provide graphics cards direct access to the processor and system memory. This avoided the limitations of the ISA bus while being less costly than a "licensed IBM MCA machine". At the time, the cost to migrate to an MCA architecture machine from an ISA machine

2668-447: The system architecture still required ISA to be present in some vestigial way internally to handle the floppy drive , serial ports , etc., which was why the software compatible LPC bus was created. ISA slots remained for a few more years, and towards the turn of the century it was common to see systems with an Accelerated Graphics Port (AGP) sitting near the central processing unit , an array of PCI slots, and one or two ISA slots near

2726-478: The system. While a handful of devices were essentially plug-n-play , this was rare. Users frequently had to configure parameters when adding a new device, such as the IRQ line, I/O address , or DMA channel. MCA had done away with this complication and PCI actually incorporated many of the ideas first explored with MCA, though it was more directly descended from EISA. This trouble with configuration eventually led to

2784-431: The then-dominant style that had one large wheel and one small wheel, which then became known as an "ordinary" bicycle. Since the end of the 19th century, most bicycles have been expected to have two equal-sized wheels, and the other type has been renamed " penny-farthing " or "high-wheeler" bicycle. The Atari Video Computer System platform was rebranded the "Atari 2600" (after its product code, CX-2600) in 1982 following

2842-490: The two sockets into one unit. These can be found in almost every AT-class PC manufactured after the mid-1980s. The ISA slot connector is typically black (distinguishing it from the brown EISA connectors and white PCI connectors). Motherboard devices have dedicated IRQs (not present in the slots). 16-bit devices can use either PC-bus or PC/AT-bus IRQs. It is therefore possible to connect up to 6 devices that use one 8-bit IRQ each and up to 5 devices that use one 16-bit IRQ each. At

2900-504: Was an ample surplus of the connector, making it inexpensive and readily available. The VESA Local Bus was designed as a stopgap solution to the problem of the ISA bus's limited bandwidth . As such, one requirement for VLB to gain industry adoption was that it had to be a minimal burden for manufacturers to implement, in terms of board re-design and component costs; otherwise, manufacturers would not have been convinced to change from their own proprietary solutions. As VLB fundamentally ties

2958-423: Was coined to distinguish the solid state of water (including exotic forms) from the solid state of other volatiles such as carbon dioxide and argon. VESA Local Bus The VESA Local Bus (usually abbreviated to VL-Bus or VLB ) is a short-lived expansion bus introduced during the i486 generation of x86 IBM-compatible personal computers . Created by VESA (Video Electronics Standards Association),

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3016-581: Was developed by a team led by Mark Dean at IBM as part of the IBM PC project in 1981. It was an 8-bit bus based on the I/O bus of the IBM System/23 Datamaster system - it used the same physical connector, and a similar signal protocol and pinout. A 16-bit version, the IBM AT bus, was introduced with the release of the IBM PC/AT in 1984. The AT bus was a mostly backward-compatible extension of

3074-544: Was introduced with the IBM PC/AT . This bus was officially termed I/O Channel by IBM. It extends the XT-bus by adding a second shorter edge connector in-line with the eight-bit XT-bus connector, which is unchanged, retaining compatibility with most 8-bit cards. The second connector adds four additional address lines for a total of 24, and 8 additional data lines for a total of 16. It also adds new interrupt lines connected to

3132-494: Was limited to 128 KiB sections, leading to problems when mixing 8- and 16-bit cards as they could not co-exist in the same 128 KiB area. This is because the MEMCS16 line is required to be set based on the value of LA17-23 only. ISA is still used today for specialized industrial purposes. In 2008, IEI Technologies released a modern motherboard for Intel Core 2 Duo processors which, in addition to other special I/O features,

3190-558: Was not until their 2004 DVD releases that the titles of the individual three films were changed to follow the same titling pattern as the Star Wars prequel trilogy (e.g. Star Wars Episode IV - A New Hope ). In the 1990s, when the Internet became widely popular and email accounts' instant delivery common, mail carried by the postal service came to be called "snail mail" for its slower delivery and email sometimes just "mail." Advances in technology and science are often responsible for

3248-765: Was not very successful, however. Later buses such as VESA Local Bus and PCI were used instead, often along with ISA slots on the same mainboard . Derivatives of the AT bus structure were and still are used in ATA/IDE , the PCMCIA standard, CompactFlash , the PC/104 bus, and internally within Super I/O chips. Even though ISA disappeared from consumer desktops many years ago, it is still used in industrial PCs , where certain specialized expansion cards that never transitioned to PCI and PCI Express are used. The original PC bus

3306-545: Was simply titled Star Wars . It was given the subtitle "Episode IV: A New Hope" for its 1981 theatrical re-release, shortly after the release of its sequel The Empire Strikes Back in 1980. Initially, this subtitle was limited to the opening text crawl, as all three films in the original Star Wars trilogy ( Star Wars , The Empire Strikes Back , and Return of the Jedi ) were still sold under their original theatrical titles on home media formats (such as VHS and Laserdisc). It

3364-626: Was substantial. MCA machines generally did not offer ISA slots, thus a migration to MCA architecture meant that any prior investment in ISA cards was made unusable. Additionally, makers of MCA-compatible cards were subject to IBM's licensing fees, which combined with MCA's greater technical requirements and expense to implement. It did have the effect of making an MCA version of a peripheral card significantly more expensive than its ISA counterpart. So while these ad-hoc manufacturer-specific solutions were effective, they were not standardized, and there were no provisions for providing interoperability. This drew

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