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DDR vs. GDDR’s


RAM memory is also used on video cards to make the video memory circuit. Until recently the video memory used the exact same technology as the system RAM memory that is installed on the motherboard. High-end video cards, however, needed memory chips faster than the ones used on the PC. So the manufacturers decided to go for DDR2 and DDR3 technologies.

DDR2 and DDR3 memories used on video card have different characteristics than the DDR2 and DDR3 memories used on the PC – especially the voltage. That’s the reason they are called GDDR2 and GDDR3 (the “G” comes from “Graphics”). While DDR works at 2.5 V, DDR2 works at 1.8 V. This leads to a lower power consumption and less heat.

GDDR2 memories continue to work at 2.5 V. Since they run at higher clock rates compared to DDR memories, they generate more heat. This is the reason why only a few video cards used GDDR2 memories.

GDDR3 memories can work at 2.0 V (Samsung chips) or at 1.8 V (chips from other manufacturers), solving the heat problem. This is the reason why this kind of memory is used by high-end video cards.

Physically speaking, both GDDR2 and GDDR3 use BGA (Ball Grid Array) packaging, the same used by DDR2 memories, as you can see on the figures.

It is a rival medium to Rambus’s XDR DRAM. GDDR4 is based on DDR3 SDRAM technology and was intended to replace the DDR2-based GDDR3, a goal it could not achieve.

GDDR4 SDRAM introduced DBI (Data Bus Inversion) and Multi-Preamble to reduce data transmission delay. Prefetch was increased from 4 to 8 bits. The maximum number of memory banks for GDDR4 has been increased to 8. To achieve the same bandwidth as GDDR3 SDRAM, the GDDR4 core runs at half the performance of a GDDR3 core of the same raw bandwidth. Core voltage was decreased to 1.5 V.

GDDR5 (Graphics Double Data Rate, version 5) SGRAM is a type of high performance dynamic random-access graphics card memory designed for applications requiring high bandwidth. Unlike its predecessor, GDDR4, GDDR5 is based on DDR3 memory which has double the data lines (“DQ” lines) compared to DDR2 but GDDR5 also has 8 bit wide prefetch buffers like GDDR4

GDDR5 (Graphics Double Data Rate, version 5) SGRAM is a type of high performance dynamic random-access graphics card memory designed for applications requiring high bandwidth. Unlike its predecessor, GDDR4, GDDR5 is based on DDR3 memory which has double the data lines (“DQ” lines) compared to DDR2 but GDDR5 also has 8 bit wide prefetch buffers like GDDR4
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