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62-918: CrossBridge uses high-performance memory-access opcodes in the Flash Player (known as "Domain Memory") to work with in-memory data quickly. CrossBridge uses the LLVM and GCC as compiler backends, in order to compile C++ code, optimize it, and transform it to run within AVM2 ( ActionScript Virtual Machine 2 ). Programs built with CrossBridge are up to 10 times faster than normal ActionScript code, but up to 2× to 10× slower than native C++ code. CrossBridge can generate Flash Player movies ( .swf files), or Flash Libraries ( .swc files), which can then be used by larger projects written in ActionScript 3 and compiled using

124-441: A mass storage cache and write buffer to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as it is not needed by running software. If needed, contents of the computer memory can be transferred to storage; a common way of doing this is through a memory management technique called virtual memory . Modern computer memory is implemented as semiconductor memory , where data

186-511: A page mode , where words of a page (256, 512, or 1024 words) can be read sequentially with a significantly shorter access time (typically approximately 30 ns). The page is selected by setting the upper address lines and then words are sequentially read by stepping through the lower address lines. With the introduction of the FinFET transistor implementation of SRAM cells, they started to suffer from increasing inefficiencies in cell sizes. Over

248-423: A DRAM, the bit line is connected to storage capacitors and charge sharing causes the bit line to swing upwards or downwards. The symmetric structure of SRAMs also allows for differential signaling , which makes small voltage swings more easily detectable. Another difference with DRAM that contributes to making SRAM faster is that commercial chips accept all address bits at a time. By comparison, commodity DRAMs have

310-406: A bug) and was based on bipolar junction transistors . It was designed by using rubylith . Though it can be characterized as volatile memory , SRAM exhibits data remanence . SRAM offers a simple data access model and does not require a refresh circuit. Performance and reliability are good and power consumption is low when idle. Since SRAM requires more transistors per bit to implement, it

372-535: A capacity of 2 = 2,048 = 2 k words) and an 8-bit word, so they are referred to as 2k × 8 SRAM . The dimensions of an SRAM cell on an IC is determined by the minimum feature size of the process used to make the IC. ‹The template Manual is being considered for merging .›   An SRAM cell has three states: SRAM operating in read and write modes should have readability and write stability , respectively. The three different states work as follows: If

434-439: A density and cost advantage over true SRAM, and without the access complexity of DRAM. In the 1990s, asynchronous SRAM used to be employed for fast access time. Asynchronous SRAM was used as main memory for small cache-less embedded processors used in everything from industrial electronics and measurement systems to hard disks and networking equipment, among many other applications. Nowadays, synchronous SRAM (e.g. DDR SRAM)

496-453: A more complex process is used in practice: The read cycle is started by precharging both bit lines BL and BL , to high (logic 1 ) voltage. Then asserting the word line WL enables both the access transistors M 5 and M 6 , which causes one bit line BL voltage to slightly drop. Then the BL and BL lines will have a small voltage difference between them. A sense amplifier will sense which line has

558-593: Is semi-volatile . The term is used to describe a memory that has some limited non-volatile duration after power is removed, but then data is ultimately lost. A typical goal when using a semi-volatile memory is to provide the high performance and durability associated with volatile memories while providing some benefits of non-volatile memory. For example, some non-volatile memory types experience wear when written. A worn cell has increased volatility but otherwise continues to work. Data locations which are written frequently can thus be directed to use worn circuits. As long as

620-400: Is volatile memory ; data is lost when power is removed. The static qualifier differentiates SRAM from dynamic random-access memory (DRAM): Semiconductor bipolar SRAM was invented in 1963 by Robert Norman at Fairchild Semiconductor . Metal–oxide–semiconductor SRAM (MOS-SRAM) was invented in 1964 by John Schmidt at Fairchild Semiconductor. It was a 64-bit MOS p-channel SRAM. SRAM

682-464: Is a system where each program is given an area of memory to use and is prevented from going outside that range. If the operating system detects that a program has tried to alter memory that does not belong to it, the program is terminated (or otherwise restricted or redirected). This way, only the offending program crashes, and other programs are not affected by the misbehavior (whether accidental or intentional). Use of protected memory greatly enhances both

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744-518: Is also embedded in practically all modern appliances, toys, etc. that implement an electronic user interface. SRAM in its dual-ported form is sometimes used for real-time digital signal processing circuits. SRAM is also used in personal computers, workstations, routers and peripheral equipment: CPU register files , internal CPU caches , internal GPU caches and external burst mode SRAM caches, hard disk buffers, router buffers, etc. LCD screens and printers also normally employ SRAM to hold

806-409: Is also used to describe semi-volatile behavior constructed from other memory types, such as nvSRAM , which combines SRAM and a non-volatile memory on the same chip , where an external signal copies data from the volatile memory to the non-volatile memory, but if power is removed before the copy occurs, the data is lost. Another example is battery-backed RAM , which uses an external battery to power

868-470: Is computer memory that requires power to maintain the stored information. Most modern semiconductor volatile memory is either static RAM (SRAM) or dynamic RAM (DRAM). DRAM dominates for desktop system memory. SRAM is used for CPU cache . SRAM is also found in small embedded systems requiring little memory. SRAM retains its contents as long as the power is connected and may use a simpler interface, but commonly uses six transistors per bit . Dynamic RAM

930-401: Is increased static power due to the constant current flow through one of the pull-down transistors (M1 or M2). This is sometimes used to implement more than one (read and/or write) port, which may be useful in certain types of video memory and register files implemented with multi-ported SRAM circuitry. Generally, the fewer transistors needed per cell, the smaller each cell can be. Since

992-469: Is less dense and more expensive than DRAM and also has a higher power consumption during read or write access. The power consumption of SRAM varies widely depending on how frequently it is accessed. Many categories of industrial and scientific subsystems, automotive electronics, and similar embedded systems , contain SRAM which, in this context, may be referred to as ESRAM . Some amount (kilobytes or less)

1054-416: Is mainly used for CPU cache , small on-chip memory, FIFOs or other small buffers. A typical SRAM cell is made up of six MOSFETs , and is often called a 6T SRAM cell . Each bit in the cell is stored on four transistors (M1, M2, M3, M4) that form two cross-coupled inverters. This storage cell has two stable states which are used to denote 0 and 1. Two additional access transistors serve to control

1116-918: Is more complicated for interfacing and control, needing regular refresh cycles to prevent losing its contents, but uses only one transistor and one capacitor per bit, allowing it to reach much higher densities and much cheaper per-bit costs. Non-volatile memory can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory , flash memory , most types of magnetic computer storage devices (e.g. hard disk drives , floppy disks and magnetic tape ), optical discs , and early computer storage methods such as magnetic drum , paper tape and punched cards . Non-volatile memory technologies under development include ferroelectric RAM , programmable metallization cell , Spin-transfer torque magnetic RAM , SONOS , resistive random-access memory , racetrack memory , Nano-RAM , 3D XPoint , and millipede memory . A third category of memory

1178-427: Is only slightly overridden by the write process, the opposite transistors pair (M 1 and M 2 ) gate voltage is also changed. This means that the M 1 and M 2 transistors can be easier overridden, and so on. Thus, cross-coupled inverters magnify the writing process. RAM with an access time of 70 ns will output valid data within 70 ns from the time that the address lines are valid. Some SRAM cells have

1240-411: Is organized into memory cells each storing one bit (0 or 1). Flash memory organization includes both one bit per memory cell and a multi-level cell capable of storing multiple bits per cell. The memory cells are grouped into words of fixed word length , for example, 1, 2, 4, 8, 16, 32, 64 or 128 bits. Each word can be accessed by a binary address of N bits, making it possible to store 2 words in

1302-482: Is physically stored or whether the user's computer will have enough memory. The operating system will place actively used data in RAM, which is much faster than hard disks. When the amount of RAM is not sufficient to run all the current programs, it can result in a situation where the computer spends more time moving data from RAM to disk and back than it does accomplishing tasks; this is known as thrashing . Protected memory

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1364-494: Is rather employed similarly to synchronous DRAM – DDR SDRAM memory is rather used than asynchronous DRAM . Synchronous memory interface is much faster as access time can be significantly reduced by employing pipeline architecture. Furthermore, as DRAM is much cheaper than SRAM, SRAM is often replaced by DRAM, especially in the case when a large volume of data is required. SRAM memory is, however, much faster for random (not block / burst) access. Therefore, SRAM memory

1426-488: Is stored within memory cells built from MOS transistors and other components on an integrated circuit . There are two main kinds of semiconductor memory: volatile and non-volatile . Examples of non-volatile memory are flash memory and ROM , PROM , EPROM , and EEPROM memory. Examples of volatile memory are dynamic random-access memory (DRAM) used for primary storage and static random-access memory (SRAM) used mainly for CPU cache . Most semiconductor memory

1488-501: The Electrotechnical Laboratory in 1972. Flash memory was invented by Fujio Masuoka at Toshiba in the early 1980s. Masuoka and colleagues presented the invention of NOR flash in 1984, and then NAND flash in 1987. Toshiba commercialized NAND flash memory in 1987. Developments in technology and economies of scale have made possible so-called very large memory (VLM) computers. Volatile memory

1550-499: The Royal Radar Establishment proposed digital storage systems that use CMOS (complementary MOS) memory cells, in addition to MOSFET power devices for the power supply , switched cross-coupling, switches and delay-line storage . 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 . NMOS memory

1612-558: The System/360 Model 95 . Toshiba introduced bipolar DRAM memory cells for its Toscal BC-1411 electronic calculator in 1965. While it offered improved performance, bipolar DRAM could not compete with the lower price of the then dominant magnetic-core memory. MOS technology is the basis for modern DRAM. In 1966, Robert H. Dennard at the IBM Thomas J. Watson Research Center was working on MOS memory. While examining

1674-550: The Whirlwind I computer in 1953. Magnetic-core memory was the dominant form of memory until the development of MOS semiconductor memory in the 1960s. The first semiconductor memory was implemented as a flip-flop circuit in the early 1960s using bipolar transistors . Semiconductor memory made from discrete devices was first shipped by Texas Instruments to the United States Air Force in 1961. In

1736-434: The computer . The term memory is often synonymous with the terms RAM , main memory , or primary storage . Archaic synonyms for main memory include core (for magnetic core memory) and store . Main memory operates at a high speed compared to mass storage which is slower but less expensive per bit and higher in capacity. Besides storing opened programs and data being actively processed, computer memory serves as

1798-561: The Arma Division of the American Bosch Arma Corporation. In 1967, Dawon Kahng and Simon Sze of Bell Labs proposed that the floating gate of a MOS semiconductor device could be used for the cell of a reprogrammable ROM, which led to Dov Frohman of Intel inventing EPROM (erasable PROM) in 1971. EEPROM (electrically erasable PROM) was developed by Yasuo Tarui, Yutaka Hayashi and Kiyoko Naga at

1860-508: The access to a storage cell during read and write operations. 6T SRAM is the most common kind of SRAM. In addition to 6T SRAM, other kinds of SRAM use 4, 5, 7, 8, 9, 10 (4T, 5T, 7T 8T, 9T, 10T SRAM), or more transistors per bit. Four-transistor SRAM is quite common in stand-alone SRAM devices (as opposed to SRAM used for CPU caches), implemented in special processes with an extra layer of polysilicon , allowing for very high-resistance pull-up resistors. The principal drawback of using 4T SRAM

1922-450: The address multiplexed in two halves, i.e. higher bits followed by lower bits, over the same package pins in order to keep their size and cost down. The size of an SRAM with m address lines and n data lines is 2 words, or 2  × n bits. The most common word size is 8 bits, meaning that a single byte can be read or written to each of 2 different words within the SRAM chip. Several common SRAM chips have 11 address lines (thus

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1984-463: The cell should be connected to the bit lines: BL and BL. They are used to transfer data for both read and write operations. Although it is not strictly necessary to have two bit lines, both the signal and its inverse are typically provided in order to improve noise margins and speed. During read accesses, the bit lines are actively driven high and low by the inverters in the SRAM cell. This improves SRAM bandwidth compared to DRAMs – in

2046-653: The cell's temperature rises. The cell power drain occurs in both active and idle states, thus wasting useful energy without any useful work done. Even though in the last 20 years the issue was partially addressed by the Data Retention Voltage technique (DRV) with reduction rates ranging from 5 to 10, the decrease in node size caused reduction rates to fall to about 2. With these two issues it became more challenging to develop energy-efficient and dense SRAM memories, prompting semiconductor industry to look for alternatives such as STT-MRAM and F-RAM . In 2019

2108-490: The characteristics of MOS technology, he found it was possible to build capacitors , and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while 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 for a single-transistor DRAM memory cell based on MOS technology. This led to

2170-459: The cost of processing a silicon wafer is relatively fixed, using smaller cells and so packing more bits on one wafer reduces the cost per bit of memory. Memory cells that use fewer than four transistors are possible; however, such 3T or 1T cells are DRAM, not SRAM (even the so-called 1T-SRAM ). Access to the cell is enabled by the word line (WL in figure) which controls the two access transistors M 5 and M 6 which, in turn, control whether

2232-428: The data when the power supply is lost, ensuring preservation of critical information. nvSRAMs are used in a wide range of situations – networking, aerospace, and medical, among many others  – where the preservation of data is critical and where batteries are impractical. Pseudostatic RAM (PSRAM) is DRAM combined with a self-refresh circuit. It appears externally as slower SRAM, albeit with

2294-597: The delay line, the Williams tube and Selectron tube , originated in 1946, both using electron beams in glass tubes as means of storage. Using cathode-ray tubes , Fred Williams invented the Williams tube, which was the first random-access computer memory . The Williams tube was able to store more information than the Selectron tube (the Selectron was limited to 256 bits, while the Williams tube could store thousands) and

2356-401: The early 1940s. Through the construction of a glass tube filled with mercury and plugged at each end with a quartz crystal, delay lines could store bits of information in the form of sound waves propagating through the mercury, with the quartz crystals acting as transducers to read and write bits. Delay-line memory was limited to a capacity of up to a few thousand bits. Two alternatives to

2418-436: The ease of interfacing. It is much easier to work with than DRAM as there are no refresh cycles and the address and data buses are often directly accessible. In addition to buses and power connections, SRAM usually requires only three controls: Chip Enable (CE), Write Enable (WE) and Output Enable (OE). In synchronous SRAM, Clock (CLK) is also included. Non-volatile SRAM (nvSRAM) has standard SRAM functionality, but they save

2480-594: The first commercial DRAM IC chip, the Intel 1103 in October 1970. Synchronous dynamic random-access memory (SDRAM) later debuted with the Samsung KM48SL2000 chip in 1992. The term memory is also often used to refer to non-volatile memory including read-only memory (ROM) through modern flash memory . Programmable read-only memory (PROM) was invented by Wen Tsing Chow in 1956, while working for

2542-518: The following types: Virtual memory is a system where physical memory is managed by the operating system typically with assistance from a memory management unit , which is part of many modern CPUs . It allows multiple types of memory to be used. For example, some data can be stored in RAM while other data is stored on a hard drive (e.g. in a swapfile ), functioning as an extension of the cache hierarchy . This offers several advantages. Computer programmers no longer need to worry about where their data

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2604-818: The free Apache Flex SDK (formerly the Adobe Flex SDK). CrossBridge also uses the GPU -based 3D rendering acceleration present in Flash Player 11 (known as Stage3D ). Using CrossBridge, Adobe ported OpenGL for use within Flash Player Stage3D and released it as an open-source project in 2012. The Lua programming language (version 5.1) was also ported to run in Flash Player using CrossBridge, and released on Google Code. CrossBridge-compiled projects also enabled running client-side digital signal processing in real-time, including fast Fourier transform and Mexican hat wavelet transform . In 2008, CrossBridge

2666-469: The higher voltage and thus determine whether there was 1 or 0 stored. The higher the sensitivity of the sense amplifier, the faster the read operation. As the NMOS is more powerful, the pull-down is easier. Therefore, bit lines are traditionally precharged to high voltage. Many researchers are also trying to precharge at a slightly low voltage to reduce the power consumption. The write cycle begins by applying

2728-540: The image displayed (or to be printed). LCDs can have SRAM in their LCD controllers. SRAM was used for the main memory of many early personal computers such as the ZX80 , TRS-80 Model 100 , and VIC-20 . Some early memory cards in the late 1980s to early 1990s used SRAM as a storage medium, which required a lithium battery to keep the contents of the SRAM. SRAM may be integrated on chip for: Hobbyists, specifically home-built processor enthusiasts, often prefer SRAM due to

2790-437: The last 30 years (from 1987 to 2017) with a steadily decreasing transistor size (node size) the footprint-shrinking of the SRAM cell topology itself slowed down, making it harder to pack the cells more densely. Besides issues with size a significant challenge of modern SRAM cells is a static current leakage. The current, that flows from positive supply (V dd ), through the cell, and to the ground, increases exponentially when

2852-449: The late 1960s. The invention of the metal–oxide–semiconductor field-effect transistor ( MOSFET ) enabled the practical use of metal–oxide–semiconductor (MOS) transistors as memory cell storage elements. MOS memory was developed by John Schmidt at Fairchild Semiconductor in 1964. In addition to higher performance, MOS semiconductor memory was cheaper and consumed less power than magnetic core memory. In 1965, J. Wood and R. Ball of

2914-447: The location is updated within some known retention time, the data stays valid. After a period of time without update, the value is copied to a less-worn circuit with longer retention. Writing first to the worn area allows a high write rate while avoiding wear on the not-worn circuits. As a second example, an STT-RAM can be made non-volatile by building large cells, but doing so raises the cost per bit and power requirements and reduces

2976-457: The memory device in case of external power loss. If power is off for an extended period of time, the battery may run out, resulting in data loss. Proper management of memory is vital for a computer system to operate properly. Modern operating systems have complex systems to properly manage memory. Failure to do so can lead to bugs or slow performance. Improper management of memory is a common cause of bugs and security vulnerabilities, including

3038-451: The memory used by other programs. This is done by viruses and malware to take over computers. It may also be used benignly by desirable programs which are intended to modify other programs, debuggers , for example, to insert breakpoints or hooks. Static random-access memory Static random-access memory ( static RAM or SRAM ) is a type of random-access memory (RAM) that uses latching circuitry (flip-flop) to store each bit. SRAM

3100-478: The memory. In the early 1940s, memory technology often permitted a capacity of a few bytes. The first electronic programmable digital computer , the ENIAC , using thousands of vacuum tubes , could perform simple calculations involving 20 numbers of ten decimal digits stored in the vacuum tubes. The next significant advance in computer memory came with acoustic delay-line memory , developed by J. Presper Eckert in

3162-439: The relatively weak transistors in the cell itself so they can easily override the previous state of the cross-coupled inverters. In practice, access NMOS transistors M 5 and M 6 have to be stronger than either bottom NMOS (M 1 , M 3 ) or top PMOS (M 2 , M 4 ) transistors. This is easily obtained as PMOS transistors are much weaker than NMOS when same sized. Consequently, when one transistor pair (e.g. M 3 and M 4 )

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3224-409: The reliability and security of a computer system. Without protected memory, it is possible that a bug in one program will alter the memory used by another program. This will cause that other program to run off of corrupted memory with unpredictable results. If the operating system's memory is corrupted, the entire computer system may crash and need to be rebooted . At times programs intentionally alter

3286-479: The same year, the concept of solid-state memory on an integrated circuit (IC) chip was proposed by applications engineer Bob Norman at Fairchild Semiconductor . The first bipolar semiconductor memory IC chip was the SP95 introduced by IBM in 1965. While semiconductor memory offered improved performance over magnetic-core memory, it remained larger and more expensive and did not displace magnetic-core memory until

3348-565: The same. Project Alchemy was commercially released as the Flash Runtime C++ Compiler. In 2013, Adobe open-sourced the Flash Runtime C++ Compiler as CrossBridge, and released it on the GitHub code hosting website. The "Premium Features" were also made free for use, and no longer required licensing or royalties. Computer memory Computer memory stores information, such as data and programs, for immediate use in

3410-444: The value to be written to the bit lines. To write a 0, a 0 is applied to the bit lines, such as setting BL to 1 and BL to 0. This is similar to applying a reset pulse to an SR-latch , which causes the flip flop to change state. A 1 is written by inverting the values of the bit lines. WL is then asserted and the value that is to be stored is latched in. This works because the bit line input-drivers are designed to be much stronger than

3472-524: The word line is not asserted, the access transistors M 5 and M 6 disconnect the cell from the bit lines. The two cross-coupled inverters formed by M 1  – M 4 will continue to reinforce each other as long as they are connected to the supply. In theory, reading only requires asserting the word line WL and reading the SRAM cell state by a single access transistor and bit line, e.g. M 6 , BL. However, bit lines are relatively long and have large parasitic capacitance . To speed up reading,

3534-434: The write speed. Using small cells improves cost, power, and speed, but leads to semi-volatile behavior. In some applications, the increased volatility can be managed to provide many benefits of a non-volatile memory, for example by removing power but forcing a wake-up before data is lost; or by caching read-only data and discarding the cached data if the power-off time exceeds the non-volatile threshold. The term semi-volatile

3596-638: Was commercialized by IBM in the early 1970s. MOS memory overtook magnetic core memory as the dominant memory technology in the early 1970s. The two main types of volatile random-access memory (RAM) are static random-access memory (SRAM) and dynamic random-access memory (DRAM). Bipolar SRAM was invented by Robert Norman at Fairchild Semiconductor in 1963, followed by the development of MOS SRAM by John Schmidt at Fairchild in 1964. SRAM became an alternative to magnetic-core memory, but requires six transistors for each bit of data. Commercial use of SRAM began in 1965, when IBM introduced their SP95 SRAM chip for

3658-533: Was initially rejected. In 1965, Benjamin Agusta and his team at IBM created a 16-bit silicon memory chip based on the Farber-Schlig cell, with 84 transistors, 64 resistors, and 4 diodes. In April 1969, Intel Inc. introduced its first product, Intel 3101, a SRAM memory chip intended to replace bulky magnetic-core memory modules; Its capacity was 64 bits (In the first versions, only 63 bits were usable due to

3720-421: Was less expensive. The Williams tube was nevertheless frustratingly sensitive to environmental disturbances. Efforts began in the late 1940s to find non-volatile memory . Magnetic-core memory allowed for memory recall after power loss. It was developed by Frederick W. Viehe and An Wang in the late 1940s, and improved by Jay Forrester and Jan A. Rajchman in the early 1950s, before being commercialized with

3782-604: Was released by Adobe as "Project Alchemy", on the Adobe Labs website. It enabled compilation of specially modified C++ projects to SWF, using the LLVM and GCC compilers. In 2012, in an attempt to monetize Flash Player, Adobe restricted use of the Stage3D and Domain Memory features of Flash Player under the "Premium Features" brand. The "Premium Features" were licensed for use and publishers were to pay royalties to Adobe for use of

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3844-453: Was the main driver behind any new CMOS -based technology fabrication process since the 1960s, when CMOS was invented. In 1964, Arnold Farber and Eugene Schlig, working for IBM, created a hard-wired memory cell, using a transistor gate and tunnel diode latch . They replaced the latch with two transistors and two resistors , a configuration that became known as the Farber-Schlig cell. That year they submitted an invention disclosure, but it

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