Computer memory and data storage types |
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Volatile |
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Embedded DRAM (eDRAM) is dynamic random-access memory (DRAM) integrated on the same die or multi-chip module (MCM) [1] of an application-specific integrated circuit (ASIC) or microprocessor. eDRAM's cost-per-bit is higher when compared to equivalent standalone DRAM chips used as external memory, but the performance advantages of placing eDRAM onto the same chip as the processor outweigh the cost disadvantages in many applications. In performance and size, eDRAM is positioned between level 3 cache and conventional DRAM on the memory bus, and effectively functions as a level 4 cache, though architectural descriptions may not explicitly refer to it in those terms.
Embedding memory on the ASIC or processor allows for much wider buses and higher operation speeds, and due to much higher density of DRAM in comparison to SRAM,[ citation needed ] larger amounts of memory can be installed on smaller chips if eDRAM is used instead of eSRAM. eDRAM requires additional fab process steps compared with embedded SRAM, which raises cost, but the 3× area savings of eDRAM memory offsets the process cost when a significant amount of memory is used in the design.
eDRAM memories, like all DRAM memories, require periodic refreshing of the memory cells, which adds complexity. However, if the memory refresh controller is embedded along with the eDRAM memory, the remainder of the ASIC can treat the memory like a simple SRAM type such as in 1T-SRAM.
eDRAM is used in various products, including IBM's POWER7 processor, [2] and IBM's z15 mainframe processor (mainframes built which use up to 4.69 GB of eDRAM when 5 such add-on chips/drawers are used but all other levels from L1 up also use eDRAM, for a total of 6.4 GB of eDRAM). Intel's Haswell CPUs with GT3e integrated graphics, [3] many game consoles and other devices, such as Sony's PlayStation 2, Sony's PlayStation Portable, Nintendo's GameCube, Nintendo's Wii, Nintendo's Wii U, and Microsoft's Xbox 360 also use eDRAM.[ citation needed ]
Product name | Amount of eDRAM |
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IBM z15 | MB | 256+
IBM's System Controller (SC) SCM, with L4 cache for the z15 | MB | 960
Intel Haswell, Iris Pro Graphics 5200 (GT3e) | MB | 128
Intel Broadwell, Iris Pro Graphics 6200 (GT3e) | MB | 128
Intel Skylake, Iris Graphics 540 and 550 (GT3e) | MB | 64
Intel Skylake, Iris Pro Graphics 580 (GT4e) | MB | 64 or 128
Intel Coffee Lake, Iris Plus Graphics 655 (GT3e) | MB | 128
PlayStation 2 | MB | 4
PlayStation Portable | MB | 4
Xbox 360 | MB | 10
Wii U | MB | 32
Computer memory stores information, such as data and programs, for immediate use in the computer. The term memory is often synonymous with the terms RAM,main memory, or primary storage. Archaic synonyms for main memory include core and store.
Static random-access memory is a type of random-access memory (RAM) that uses latching circuitry (flip-flop) to store each bit. SRAM is volatile memory; data is lost when power is removed.
Dynamic random-access memory is a type of random-access semiconductor memory that stores each bit of data in a memory cell, usually consisting of a tiny capacitor and a transistor, both typically based on metal–oxide–semiconductor (MOS) technology. While most DRAM memory cell designs use a capacitor and transistor, some only use two transistors. In the designs where a capacitor is used, the capacitor can either be charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1. The electric charge on the capacitors gradually leaks away; without intervention the data on the capacitor would soon be lost. To prevent this, DRAM requires an external memory refresh circuit which periodically rewrites the data in the capacitors, restoring them to their original charge. This refresh process is the defining characteristic of dynamic random-access memory, in contrast to static random-access memory (SRAM) which does not require data to be refreshed. Unlike flash memory, DRAM is volatile memory, since it loses its data quickly when power is removed. However, DRAM does exhibit limited data remanence.
Magnetoresistive random-access memory (MRAM) is a type of non-volatile random-access memory which stores data in magnetic domains. Developed in the mid-1980s, proponents have argued that magnetoresistive RAM will eventually surpass competing technologies to become a dominant or even universal memory. Currently, memory technologies in use such as flash RAM and DRAM have practical advantages that have so far kept MRAM in a niche role in the market.
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Semiconductor memory is a digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to devices in which data is stored within metal–oxide–semiconductor (MOS) memory cells on a silicon integrated circuit memory chip. There are numerous different types using different semiconductor technologies. The two main types of random-access memory (RAM) are static RAM (SRAM), which uses several transistors per memory cell, and dynamic RAM (DRAM), which uses a transistor and a MOS capacitor per cell. Non-volatile memory uses floating-gate memory cells, which consist of a single floating-gate transistor per cell.
VLSI Technology, Inc., was an American company that designed and manufactured custom and semi-custom integrated circuits (ICs). The company was based in Silicon Valley, with headquarters at 1109 McKay Drive in San Jose. Along with LSI Logic, VLSI Technology defined the leading edge of the application-specific integrated circuit (ASIC) business, which accelerated the push of powerful embedded systems into affordable products.
POWER7 is a family of superscalar multi-core microprocessors based on the Power ISA 2.06 instruction set architecture released in 2010 that succeeded the POWER6 and POWER6+. POWER7 was developed by IBM at several sites including IBM's Rochester, MN; Austin, TX; Essex Junction, VT; T. J. Watson Research Center, NY; Bromont, QC and IBM Deutschland Research & Development GmbH, Böblingen, Germany laboratories. IBM announced servers based on POWER7 on 8 February 2010.
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1T-SRAM is a pseudo-static random-access memory (PSRAM) technology introduced by MoSys, Inc. in September 1998, which offers a high-density alternative to traditional static random-access memory (SRAM) in embedded memory applications. Mosys uses a single-transistor storage cell like dynamic random-access memory (DRAM), but surrounds the bit cell with control circuitry that makes the memory functionally equivalent to SRAM. 1T-SRAM has a standard single-cycle SRAM interface and appears to the surrounding logic just as an SRAM would.
A multi-chip module (MCM) is generically an electronic assembly where multiple integrated circuits, semiconductor dies and/or other discrete components are integrated, usually onto a unifying substrate, so that in use it can be treated as if it were a larger IC. Other terms for MCM packaging include "heterogeneous integration" or "hybrid integrated circuit". The advantage of using MCM packaging is it allows a manufacturer to use multiple components for modularity and/or to improve yields over a conventional monolithic IC approach.
Microsoft XCPU, codenamed Xenon, is a CPU used in the Xbox 360 game console, to be used with ATI's Xenos graphics chip.
The transistor count is the number of transistors in an electronic device. It is the most common measure of integrated circuit complexity. The rate at which MOS transistor counts have increased generally follows Moore's law, which observes that transistor count doubles approximately every two years. However, being directly proportional to the area of a die, transistor count does not represent how advanced the corresponding manufacturing technology is. A better indication of this is transistor density which is the ratio of a semiconductor's transistor count to its die area.
The Hollywood chipset, a key component of Nintendo's Wii video game console, is a system on a chip (SoC) that integrates a graphics processing unit (GPU), I/O interfaces, and audio capabilities. Designed by ATI, it was manufactured using a 90 nm or 65 nm CMOS process, similar to the Wii's central processing unit, Broadway.
Haswell is the codename for a processor microarchitecture developed by Intel as the "fourth-generation core" successor to the Ivy Bridge. Intel officially announced CPUs based on this microarchitecture on June 4, 2013, at Computex Taipei 2013, while a working Haswell chip was demonstrated at the 2011 Intel Developer Forum. Haswell was the last generation of Intel processor to have socketed processors on mobile. With Haswell, which uses a 22 nm process, Intel also introduced low-power processors designed for convertible or "hybrid" ultrabooks, designated by the "U" suffix. Haswell began shipping to manufacturers and OEMs in mid-2013, with its desktop chips officially launched in September 2013.
Random-access memory 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, where 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.
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