*New SIS P4 Chipet to support PC2700 DDR SDRAM -shipped B4 end of year

[damocles]

Xbit

Almost all the Taiwanese chipset makers are planning to release their DDR solutions for Pentium 4 CPU by the end of the year. However, the most successful product showing the best performance is very likely to be SiS645. Why? Well, as to the info we found here, SiS645 will be the only Pentium 4 core logic supporting PC2100 DDR SDRAM but also faster PC2700 DDR SDRAM working at 333MHz and featuring 2.7GB/sec bandwidth. This memory bandwidth is very close to that of Pentium 4 Quad Pumped processor bus working at 400MHz. This facts as well as low memory latency give SiS645 every chance to become an indisputable performance leader among Pentium 4 DDR chipsets.

SiS is gaining some momentum with an intergrated P4 chipset due in the first Quarter of next year

 

[Scouzer]

WOOT! It'd be perfect if it was dual channel, but eh its good enough I think!

 

[shathal]

Hmm - interesting.

But dual-channel (hyophetical, I know - going dual channel DDR/SDRAM is just too expensive to implement) wouldn't really benefit things.

You'd have a CPU bus bandwidth of 3.2 GB/s and a Memory bandwidth of 5.4 GB/s.

By the time the P4 gets 133 MHz FSB, I would expect the RIMMs to be there as well - 1066 MHz, if I am not mistaken.

So - nice thought, but not really feasable.

 

[MadRat]

I'm guessing that the P4 isn't bound to running synchronous with the memory anyhow, so why not a 133fsb with the PC800? The Intel 850 chipsets will be limited to synchronous transfers, but VIA and SiS are not. Its likely the Intel 845 chipset is not synchronous, too.

Sure 100fsb x 4-channels = 400fsb, but we know also that the channels don't necessarily have to run in step with the FSB. The Apollo 133 showed that it was possible to run FSB and memory in an asynchronous environment with minimal impact to performance. In some ways the performance was better, being that the CPU was able to run much harder than the limited memory at that time.

It would be interesting to see the difference in PC800/1066, FSB's at 100/133fsb, and a 4:3/3:4 ratio of memory to processor speed, vice versa.

• 400fsb memory and 533fsb CPU
• 533fsb memory and 400fsb CPU

One could really learn alot about the P4's architecture in this way. Once and for all we could put to rest that the "future P4 needs the increased bandwidth" argument.

 

[shathal]

400 MHz FSB CPU will not gain anything by moving from PC800 to PC1066 RIMMs. It's bus bandwidth still tops at 3.2 GB/s.

It would be "wasted" - the same as PC800 ... unless you want to upgrade to a 533 MHz FSB CPU eventually...

My guess at any rate - doubt I am wrong on that one. Will see for definite once we get there, I guess .

 

[MadRat]

shathal-

It will lend us the knowledge whether a P4 realy uses all of its bandwidth. Most likely it does not. I'm guessing the 845 chipset runs its 15-20% slower due to some sort of asynchronous transfer issue, not because of the bandwidth it serves up.