VIA Roadmap: Interesting P4X333 info

[Athlon4all]

I came across this VIA roadmap from none other than VIA Hardware. It had some very interesting info on P4X333. Apparantley it's not just a DDR333 version of P4X266. Let me quote them:

<< The P4X333 will be VIA?s next P4 chipset with support for the new DDR333 standard. The P4X333 is more then just a P4X266 with support for DDR333. It also adds support for AGP8x, V-Link 533mb/s, and an accompanying VPX-II PCI-X bridge. It also features support for QDR, which doubles the bandwidth of DDR333 modules to 4.2GB without utilizing Dual Channel memory architecture. >>

Sounds good, Better V-Link, AGP 8X, PCI-X Support, but what really caught my eye was use of QDR, but still using PC2700 w/o dual channels. What do you think that's about? That's big because at the end of the year while Tulloch/PC1066/533MHz fsb P4's aren't out yet, VIA if they get past the lawsuits will have the highest max theoretical bandwidth chipset for P4. But there's something odd, if it doubled wouldn't that translate to 5.4GB/ps, maybe they're talking about when using PC2100. Just thought I'd pass this on.

 

[Rand]

<< but what really caught my eye was use of QDR, but still using PC2700 w/o dual channels. What do you think that's about? >>



Their getting 5.4GB/s with PC2700 modules. They don't need a dual channel configuartion in order to do this as all their doing is basically switching the DRAM banks within a cycle to double effective bandwidth.
If anyone has anymore information regarding how their accomplishing this please post.

 

[majewski9]

I thought PC2700 was being developed for use with Hammer and not p4? I think that Intel is going to be releasing a new RDRAM chipset next year.

 

[pm]

Interesting stuff, Athlon4all. Thanks for the link and the post. Pretty exciting stuff.

<< If anyone has anymore information regarding how their accomplishing this please post. >>

Rand, are you look for details of how QDR works or are you looking for how Via implemented it? The former I can find (with a bit of searching... there's a couple of good articles on QDR at EETimes, and there's one official site that has a couple of details), the latter I have no idea.

 

[Rand]

<< Rand, are you look for details of how QDR works or are you looking for how Via implemented it? The former I can find (with a bit of searching... there's a couple of good articles on QDR at EETimes, and there's one official site that has a couple of details), the latter I have no idea. >>



I already have a fairly good grasp of QDR, so I'm trying to get a better understand of how VIA has implemented this.
Unfortunately I don't think anybody besides VIA really knows much in the way of details on their implementation thus far.

Might you have any idea whether this would require any kinds of changes to the existing specification for DDR SDRAM in order to work effectively with the P4X333?

BTW, nice to see you outside of the HT forum for once PM

 

[pm]

<< Might you have any idea whether this would require any kinds of changes to the existing specification for DDR SDRAM in order to work effectively with the P4X333? >>

It's my understanding that they are very few. Since this is more of an implementation issue, most of the changes are required by the chipset and the motherboard routing. IIRC, some setup timings are tighter, but you could relax these by increasing the latency and then program these into the SPD. But it's my understanding that current DDR SDRAM can work in a QDR board with little change besides being characterized for it on a tester (ie. the memory manufacturer: "This memory is tested to work in a QDR board").

 

[Rand]

Thanks for the info PM.

 

[Sohcan]

I heard rumors about this at Ace's a while back...it's kind of like "interleaving" with multiplexing. The memory bus is QDR, and half the signal is multiplexed to DIMM bank A, the other half to DIMM bank B. Pretty cool stuff....it just requires signalling and memory controller changes on the motherboard, but it most likely can use existing DDR SDRAM DIMMs and the same number of motherboard traces.



<< I thought PC2700 was being developed for use with Hammer and not p4? >>

The PC2700 spec has been in development for general use for some time, it wasn't specifically developed for Hammer.

edit: There's some more info about this at Ace's.

 

[Athlon4all]

Good stuff guys thanks. Looks like it could be the highest performing P4/Northwood solution.