Sometime late next summer or early fall, Rambus will come up with its answer to dual channel DDR: quad channel RDRAM.

Should you care?


Premium RDRAM seems to be running at a 50%+ premium over high-end DDR. A typical quadchannel RDRAM system will probably consist of two 256MB RIMM4800 sticks (RIMM4200 and 4800 means two channels of RDRAM on one memory stick.)

In all likelihood, that will cost $100-125 more than an equivalent high-end DDR system; $300-325 vs. $200.

Significant, but not an automatic killer.

Motherboards will also likely cost somewhat more than current RDRAM designs simply because it will be more complicated to do and may require thicker PCB boards, but we’ll have to see about that.


The theoretical maximum memory bandwidth for quadchannel RDRAM is 9.6Gb/sec. This is 50% more than dual DDR’s theoretical max.

Theory isn’t reality. A quad-channel RDRAM system will probably have more overhead than a dual-channel system.

For right now, a good ballpark figure can be derived from just remembering how much of a performance edge the original dual-channel RDRAM had over single-channel DDR: 5-7%.

So if you need to think about it right now, figure on an extra $100-125 for an extra 5-7% average real performance.

Too Much Of A Good Thing?

We know that increasing memory bandwidth doesn’t automatically improve everything even now. A lot of applications simply don’t need any more than they already have, and they show little to no improvement even you give them more.

There is the possibility that we’ll reach the saturation point for even many or most games as we jump to dual-channel DDR or quad-channel RDRAM. It would be surprising if at least some older games don’t reach their limits.

While it’s pretty safe to assume there is a wall at some point, we just don’t know where that wall is. We may see it with dual DDR400. We may see it with quad RDRAM. We might not see it at all at this point.

In all likelihood, we’ll start seeing it pop up with dual DDR 400, and see more of it with quad RDRAM, but it’s something to look for. Two or six months from now, if certain gaming benchmark scores on these future PIV systems barely budge despite much more bandwidth, that’s likely the reason.


Once the premium price of RDRAM dipped below ludicrous levels, RDRAM-based systems became a nice little niche in the overall PC market.

Substituting SiS for Intel is probably a strike against RDRAM, but presuming SiS can provide good stable chipsets, we’ll probably see much the same with quad-channel RDRAM systems: a premium niche offering a little more performance at a hefty but not huge price.

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