DDR vs. GDDR Memories
By Gabriel Torres on July 20, 2005


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 cards 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.”

In our DDR2 Memory Tutorial we explained the differences between DDR and DDR2 memories. As we mentioned there, one of the main differences is the voltage. While DDR works at 2.5 V, DDR2 works at 1.8 V. This leads to 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 – only GeForce FX 5700 Ultra and GeForce FX 5800 Ultra used this kind of memory. Shortly after GeForce FX 5700 Ultra was released, many video card manufacturers released a GeForce FX 5700 Ultra using GDDR3 memories, maybe to lower the heat and power consumption effects.

GDDR2
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Figure 1: GDDR2 memory

GDDR3
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Figure 2: GDDR3 memory

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

DDR3 memories have not been released for PCs yet, but they will probably work at 1.5 V, which is different from GDDR3 memories.

Physically speaking, both GDDR2 and GDDR3 use BGA (Ball Grid Array) packaging, the same used by DDR2 memories, as you can see in the figures. It is impossible to visually detect whether a memory chip is GDDR2 or GDDR3. The solution is to search on Google or on the manufacturer’s website for its part number (K4N26323AE in Figure 1 and K4J55323QF in Figure 2, for example).

Originally at http://www.hardwaresecrets.com/article/DDR-vs-GDDR-Memories/168


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