Asus 4870 X2

[THERESONATOR]

Hi

I like to buy the best of the best of the best when I buy a computer (within reason), which is why I want to shell out and buy a Asus 4870X2 for the Rampage Extreme II w/ the Core i7 920 I'm gonna get. I believe this motherboard features PCI Ex lane output for Crossfire of 16x/16x/8x. Which I would be fine with if I was buying just ordinary single GPU solutions. But seeing as there are two GPUs on each of these 4870X2's I buy, I am left wondering: does having one 4870X2 on a single slot reduce its output to each GPU to 8x?

The net effect of that scenario is of course me buying two 4870X2's only to find that I would've got the exact same output if I bought instead two single GPU 4870's. In terms of numbers I would be getting 8x/8x/8x/8x - but on two PCI Express slots. Its kinda like that for my current setup.

I only managed to get SLI last month on my 2 year old computer (DFI Skt 939 SLI-DR Expert w/ two BFG 7800GTXs) only to find that the board only supported an output of 8x/8x for both, net effect = same as having one card on a single x16 slot. I was really pi$$ed off with that. OK so it only cost me £40 (and far too much time to find a EXACT same card that is now way after-market and discontinued so that it would be compatible.. thanks eBay) but I don't want to go through that kind of pain again! So I'm doing my homework here.

What else really got my back up was when I bought Vista 64 the other day, only to find that it doesn't support my DX9 SLI cards! GRR!

OK so back to the question.

I want quad Crossfire with 16x to each GPU. Would I be able to get that with two 4870X2's in a Asus Rampage Extreme II, or is this not yet supported on any motherboard to date?

TIA.

 

[masteryoda34]

The bandwidth difference between 16x and 8x on PCI-E 2.0 makes no difference in real world applications. And secondly, the 4870 X2 uses an internal bridge chip for the PCI-E connection. See the chip between the two GPU's on this picture 4870 X2 PCB

So your question doesn't really have an answer and furthermore, it is irrelavent.

 

[betasub]

Originally posted by: THERESONATOR
I only managed to get SLI last month on my 2 year old computer (DFI Skt 939 SLI-DR Expert w/ two BFG 7800GTXs) only to find that the board only supported an output of 8x/8x for both, net effect = same as having one card on a single x16 slot. I was really pi$$ed off with that. OK so it only cost me £40 (and far too much time to find a EXACT same card that is now way after-market and discontinued so that it would be compatible.. thanks eBay) but I don't want to go through that kind of pain again! So I'm doing my homework here.

You really think PCIe lane bandwidth was limiting your 7800GTX SLI? Even for PCIe v1 @8x, there's far more bandwidth than the 7800GTX would ever need. (With faster cards, FSX can provide an exception).

As for your single 4870X2 question, masteryoda is correct that inter-GPU traffic is handled over an internal bridge (AFAIK ATI haven't implemented the sideport yet). GPU-system communication is over the motherboard's PCIe2 @16x.

The quadfire question depends entirely on how Asus have configured the PCIe2 lanes on the Rampage II Extreme. Because it has the X58 chipset with 36 PCIe2 lanes, 16/16/8x isn't going to happen: 16/16/disabled? for dual cards, 16/8/8 for triple set-ups. For more on X58 and the Asus Rampage II Extreme, see Anand's motherboard reviews, such as here.