Video memory
Memory that stores datas which are shown and which will be presented on screen are called video memory and it is usualy implemented on graphics card itself. First graphics cards used standard dynamic memory, but that requested constant refresh of memory content. Consequences were reducition of performances, which could be seen with slight increase of frequencies of GPU and GPU.Advantage of video memory implementation is very high possibility of adjusment for specific purpuses, which resulted with creation of new memory technologies. Video RAM is special type of dynamic memory that allowed momental reading and writing of datas. It also doesn't demand big refresh rate, like standard dynamic memory, which gives much better work performanses like standard dynamic memory, which can give better performances.
EDO RAM is like ordinary DRAM, with exception that it gives better throughput and can work on higher frequencies. It also accelerates read/write cycle, which execute more efficient then standard dynamic memory.
SDRAM/SGRAM memory is also used on graphics cards. SDRAM allows that memory and graphics processor work on their own frequencies and it is used for efficient gathering and data process, that allows more efficient work then EDO memories. SGRAM is just variation of SDRAM, but is used only as video memory, and it supports read/write blocks and data processing on bit level, which resulted with higher performances. Graphics cards use this memory, but haven't registered significant use.
Today, DDR memory is mostly used in this purpose, aldo there exist modules that use GDDR3 memory which we can find on high end graphics cards where work frequences are higher, so is bigger bandwith for aproximatting of high performanses.
DDR memory for graphics cards we can find in 2 different packages:
-TSOP-II, 66-pin (with 33 pin with both sides), this package is relatively cheap, easy to embedd and manufacture process is fast, thanks to technology improvements.
-FBGA, 144 pin. These memories usualy can have speeds from DDR350 MHz or 400 MHz (effective 700 MHz and 800 MHz). Memories with this package are also embadded on high end graphics cards. It is familiar that DDR memory can work up to maximum frequency of 500 MHz (effective 1 GHz), but those models is very difficult to produce so price of these memories is pretty big.
Because of these reasons, graphics cards that use DDR memory, working frequences memory is set up at 350 MHz, or max 400 MHz as upper limit.
Example of GDDR3 memories on newest graphics cards is pretty universal. GDDR3 technology is equal to DDR2 technology of system memories, and it uses 4-bit preprocessing of datas, which cause for effective frequency to be 4 times bigger then real work frequency, and that is twice as double then equalent DDR memory, and it makes data transmition easier.
Starting work frequencies GDDR3 memory is 500 MHz, and theortethicaly in this moment it is able to reach working frequencies up to 800 MHz. Using only FBGA package, and modules are phisicaly small and don't get heated to much, which allows them to work on bigger frequencies without need for coolers
Therefore, strongest graphics memories today are separated to DDR and GDDR3. Though, future could be XDR and GDDR4 memories that sould offer not just bigger working frequencies, but also bigger memories bandwith that would go up to 100GB/s.
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