Om je vraag alvast te beantwoorden (je zocht het nl. niet voor niets op
):
SGRAM = SDRAM maar dan met extra functies. De
G staat voor Graphics om aan te geven dat het om een hiervoor gespecialiseerd type gaat. Om deze reden is het in die specifieke toepassingen iets sneller als normaal SDRAM van dezelfde rating.
Q2 What's the difference between EDODRAM, SDRAM and SGRAM?
A2 Generally, SDRAM and SGRAM have more high bandwidth than EDO because of the difference in structure and access time. And SGRAM has some special command registers and operations to speed up graphics data accessing, and SDRAM has not such function. So SGRAM is used by majority 3D graphics cards.
Bron:
http://www.qdigrp.com/qdisite/eng/support/f_agp1.htm
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SGRAM is a video-specific extension of SDRAM that includes graphics-specific read/write features. SGRAM also allows data to be retrieved and modified in blocks, instead of individually. This reduces the number of reads and writes that memory must perform and increases the performance of the graphics controller by making the process more efficient.
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http://www.kingston.com/tools/umg/umg05a.asp
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http://www.highlandergsa....al/MEMORYtechnologies.pdf
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http://www.kingston.com/t...G%20sections/umg55_60.pdf
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SGRAM: Synchronous Graphics RAM a single-ported RAM type. It speeds performance through a dual-bank feature, in which two memory pages can be opened simultaneously; it therefore approximates dual-porting. SGRAM is proving to be a significant player in 3-D video technology because of a block-write feature that speeds up screen fills and allows fast memory clearing.
Bron:
http://www.epanorama.net/links/memory.html
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Synchronous Graphics RAM (SGRAM) is clock-synchronized random access memory that is used for video memory. It is relatively low-cost video memory. It uses masked write, which enables selected data to be modified in a single operation rather as a sequence of read, update, and write operations. It also uses block write, which allows data for background or foreground image fills to be handled more efficiently. SGRAM is single-ported. Its special features are what make it a moderately fast form of video memory. The Matrox Mystique is an example of a video card that uses SGRAM.
Bron:
http://whatis.techtarget....0,,sid9_gci214202,00.html
GDDR = DDR SGRAM, in principe hetzelfde als hierboven dus, maar dan in Double Data Rate uitvoering.
GDDR2:
Enter GDDR2 SDRAM
Why are graphics heavyweights ATI and Nvidia jumping ahead of everyone else, including JEDEC, with their own proprietary versions of DDRII? Because as the GPU has gained ground in the PC performance hierarchy, so have the requirements of SGRAM memory, or video memory.
Indeed, the graphics processor world has seen many great advances during the past few years -- many a result of the slugfest between ATI and Nvidia to offer the best graphics card capable of matching the best games out there (anyone who has played Halo or Unreal with a Radeon or GeForce video card online late past midnight, only to call in sick at work or skip school the next day, knows this). In many respects, after a certain clock-speed threshold has been reached, the distinguishing factors of the GPU have become more crucial for graphics performance; and, in order to match the GPU's processing capabilities, ultra-high performance memory must be on the menu as well.
Micron is well aware of this, and along with Samsung and Hynix, has begun developing graphics DDRII memory prior to the finalization of a graphics DDRII standard by JEDEC, which is slated for this summer. This memory, now known as GDDR2, will do a lot to accommodate the powers of ATI's latest Radeon and Nvidia's GeForceFX, as well as other vendors' goods, such the latest devices from Trident or S3 with 1-Ghz of bandwidth.
DDR's double-fetch-per-cycle capability for graphics has helped, but in a recent patent filing Micron has indicated that a burst operation is required, which Micron defines as an operation retrieving a given number of data stored at sequential locations within the memory.
Additionally, GDDR2 will include a memory array that is addressable by even and odd word addresses. The logic circuitry with a burst increment mode will access the array starting at an even word address, and a burst decrement mode will access the array starting at an odd word address.
Within the scope of Micron's burst mode, the memory device has a burst increment mode when starting at an even word address, and a burst decrement mode when starting at an odd word address. Data increments are counted, so that the second data word retrieved is still from the same memory location as the first data word as addressed by the logic circuitry. When starting at an odd word address, the device counts down (decrements), so that the second data word retrieved is still from the same memory location as the first data word as addressed by the logic circuitry.
GDDR3:
But, as if GDDR2 were not enough for the GPU when it now looks as if DDRII for CPU chipsets may not see wide-scale application before 2005, Micron, Infineon, Elpida, and Hynix says they will have samples of GDDR3 this year.
If you have not guessed already, Micron has been very forthcoming about the technical details of its future products, including information about its flavor of GDDR3, and says it will have samples before the first half of 2003 has passed. According to Micron, instead of the 2n-prefetch used with DDR, GDDR3 will offer a 4n-prefetch rate that transfers four data bits every two clock cycles at the I/O pins. A single read or write access for GDDR3 will consist of a single, 4n-bit-wide data transfer at the internal DRAM core. The 4n-prefetch will thus enable the internal data bus to be four times the width of the external data bus, and will enable the external data transfer rate to be four times the internal column cycle time.
GDDR3, Micron says, will also employ "pseudo open drain logic," which accounts for the I/O interface and simplifies data clocking by having all tri-stated data strobes "float" to a natural Logic, Micron says. The bus is dual-end terminated using the 40Ω controlled impedance driver at the source and the 60Ω on-die termination to VDD at the destination.
Unlike a pure open drain scheme, source termination is achieved on LOW-to-HIGH transitions by using the PMOS device of the push driver. DC power is also minimized since it is only consumed when a logic LOW is driven onto the bus.
GDDR3 also utilizes an external precision resistor (RQ) tied to VSS to calibrate the driver to a known value. Micron says that this eliminates most of the process variation that can be introduced during manufacturing. Initially, the driver functions as a standard push-pull driver with multiple legs to tune the impedance and adjust the on-die termination resistor (RQ) to be six times the desired driver impedance. The PMOS device is first calibrated to the resistor tied to ground. This calibrates one PMOS leg to 240Ω. The pull-up stage for this output buffer consists of six legs, which is the nominal 40Ω equivalent pull-up driver. After the PMOS leg is calibrated to the external resistor, the NMOS leg is calibrated to the PMOS leg in a similar fashion.
After the process variations have been eliminated, the only other factors that need to be addressed are voltage and temperature variations that occur over time in the system. To address these two issues, the GDDR3 driver provides periodic updates to recalibrate, which minimizes the variation in the pull-up and pull-down drive current due to voltage and temperature. Updates currently take place at a minimum of every 70µs during AUTO REFRESH commands, but this can be adjusted to as small of an interval as needed. The initial calibration takes approximately 350 clock cycles, but the recalibration and updates take less than one clock cycle. The only time the output driver cannot be recalibrated is when there is read data on the bus.
Laatste quotes:
http://students.ceid.upat...n/Articles/RAM%20Wars.htm (
google cache)
Wat betreft plaatsing van dergelijke gegevens in een Faq: als het niet veel gevraagd is, is het geen Faq meer
Bovenstaande heb ik bijvoorbeeld gevonden met Google. Een Faq is natuurlijk niet het enigste naslagwerk voor info
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Voor 90% gewijzigd door
Verwijderd op 19-10-2003 21:59
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