Rambus = PC1600 DDR?

[Guest]

According to what I've been reading Rambus RDRAM has a bandwidth of 3.2 GB/sec when running dual channel on a P4 setup, but if it were running single channel it would equal out to 1.6 GB/sec, the same as PC1600 DDR. But from what I understand RDRAM is also cursed with a higher latency.

If this formula is correct, doesn't this make RDRAM essentially inferior to DDR? So it only would make sense that even a dual-channel PC1600 DDR chipset would equal the same performance as RDRAM, but a dual-channel PC2100 (or even PC2400 or PC2700) would be superior to the more expensive RDRAM.

Is this close to accurate or am I way off target?

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[FatBurger]

I believe that is basically correct. However, saying RDRAM has higher latency is not strictly true. It has higher latency fo the first read, but as it accesses memory in order, the latency goes down very far.

Block 1........block 2.....block 3...block 4..block 5..block 6.........block 8

DDR, on the other hand, is a constant latency.

Block 1....block 2....block 3....block 4....block 8....block 9....block 5....block 6....block 118

Make sense?
It's a give and take.

Anyhow, you're correct. DDR is actually better than RDRAM, but there is no dual-channel DDR, so an RDRAM platform has better bandwidth than a DDR platform. If SiS releases a dual-channel DDR chipset for the P4, it will be a thing of beauty. I'd probably go with P4 at that point. Assuming that I have the money to do it at the time. I'd also want to go with SCSI, though. The hard drives would become a real bottlenck. Anyhow, I'm off the topic...



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[Guest]

That's probably what I'm most curious to see is how well the nForce chipset performs, which is supposed to use dual-channel DDR. If it does well I can't imagine Intel being too persistent on staying with RDRAM. In fact right now I've been looking at the VIA chipset for the P4 to match it up with DDR, if they were able to utilize a dual-channel memory controller and make it work that would be awesome.

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[FatBurger]

The nForce is looking worse every day to me. The only thing left that I like is the good onboard sound and he onboard networking. But since I own what I need of that in the form of cards inhabiting my PCI slots...

The AMD Athlon/Duron/Tbird/Palamino/Morgan/whatever cannot at this time utilize the increased memory bandwidth that dual-channel DDR has to offer. It would help some, since it would finally achieve the full potential of single-channel DDR, but current AMDs are only able to use 2.1GB/s of memory bandwidth.

A P4 with dual-channel DDR, on the other hand...



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[rcf84]

SiS isn't releasing Dual Channel DDR but DDR333 support giving it 2.7gb's of bandwith.

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[rcf84]

DDR333 = PC2700

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[FatBurger]

Oh? I heard they were, I'll try to remember where I saw that.

Does anyone know the memory bandwidth limitation of a P4? Someone told me it was 1.4GB/s, or something ridiculous like that.

Edit:
Nope, found it <A HREF="http://channel.intel.com/business/ibp/processor/pentium4.htm" target="_new">here</A>.

The massive 3.2-gigabytes-per-second bus on the Pentium 4 processor is balanced by 3.2-gigabytes-per-second of memory bandwidth.

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[juin]

To what i have read P4 FSB can go at """any time""" at 533 mghz 4*133 for the use of pc 1066.It just Non official support.

 

[FatBurger]

Could very well be. That wouldn't help much though, since the P4 is already pretty much at the same limit as RDRAM.
It'd help, of course. Just wouldn't get the full effect for memory bandwidth reasons.



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[Raystonn]

You would in essence be overclocking the CPU by upping it to an equivolent of a 533MHz system bus. If your CPU and memory can both handle it, it would increase your system's memory bandwidth and your CPU's clockspeed. This seems to be the holy grail of P4 overclocking at the moment. You just need to find the higher speed memory and get decent cooling for the CPU. Any word on PC1066 RDRAM? I haven't seen any new information on this for a while at my end. Maybe we should push Samsung to move more quickly on it.

-Raystonn


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[FatBurger]

<A HREF="http://www.pcworld.com/resource/printable/article/0,aid,52884,00.asp" target="_new">Here</A> is a little over month old article saying to expect it sometime 2002.



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