Everything You Need to Know About GDDR MemoryWritten by Michael Brown | 09/16/08 at 01:11:36 AM
We invariably refer to the video memory in modern videocards as GDDR, differentiating it only by version (GDDR2, GDDR3, GDDR4, and now GDDR5), but the technology’s full acronym is actually GDDR SDRAM, which stands for Graphics Double Data Rate Synchronous Dynamic Random Access Memory.
“Double data rate” describes the memory’s capacity for double-pumping data: Transfers occur on both the rising and falling edges of the clock signal. This endows memory clocked at 800MHz with an effective data-transfer rate of 1.6GHz. “Synchronous” refers to the memory’s ability to operate in time with the computer’s system bus. This allows the memory to accept a new instruction without having to wait for a previous instruction to be processed, a practice known as instruction pipelining.
GDDR2 memory was never a very popular solution among GPU manufacturers: The technology required 2.5 volts to power its input buffers and core logic (i.e., VDD voltage), which is the same as GDDR. GDDR2 operated at much higher clock speeds than its predecessor, however, which produced a tremendous amount of heat. The fact that GDDR2’s VDDQ voltage requirement (the electricity needed to power the memory’s output buffers) was only 1.8 volts didn’t compensate for this problem.
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