HEXUS.reviews :: CrossFire and SLI dongle-less/bridgeless performance analysis

[Steve]

Bridgeless and dongle-less multi-GPU rendering isn't exactly new. We've seen it on lower-end SLI and CrossFire solutions, but now it's starting to rear its head higher up the product ranges, where the lack of a dedicated inter-card link might have a bigger impact. Shall we see if it does? OK then!

http://www.hexus.net/content/item.php?item=6683

[YorkieBen]

a quick comment...

afaik ATI when mentioning dongleless crossfire said that a motherboard with 2 16xspeed pci-e slots would be required (not 2 8xspeed slots like the x975 chipset) as this would give enough pci-e lanes for the bandwidth to not be an issue.

As you tested a board with 2 16xspeed lanes (Nforce590) against one with 2x 8speed lanes surely this test is not totally fair.

Although I realise Core2Duo does not have any crossfire mobos with dual 16xspeed slots until RD600 arrives, you could have used an amd-based system as although it would have been slower overall it would imo show a fairer comparison.

e.g. the Asus ASUS M2R32-MVP vrs the Asus M2N32-SLi?

just my 2 pence, otherwise an interested review

[shaithis]

If anyone thinks that the merger will force people to pair AMD + ATI and Intel + nVidia, I think they are quite short-sighted.

It would be killer for the companies to effectively lock people in more then they are now at the same time as narrowing their potential customer base.

I am sure for now, there are some confused people and that is the reason the RD600 seems up-in-the-air, but give it a couple of months and i think we will be back on track

[Elessar_VPR]

I find it a little odd when looking at the Crossfire Splinter Cell results you suggested the dongle may not be performing as well as it could, despite getting an increase of 97% over the single X1900GT. Seems like it's more a case of the non-dongled version doing well than the dongle doing bad to me.

Still overall was quite interesting.

[Dazz]

I completely agree having 8x8 vx 16x16 is unfair, thry it on a RD580 board you will find crossfire improves around 15+%, or so the case was with dual X1600XT cards in 16x16 board then over a 8x8 which people tested a ASUS MPV Vs and ASUS MPV32 sk939. At the moment this is not apples to apples as nvidia have a 100% bandwith peformance increase.

[Steve]

I find it a little odd when looking at the Crossfire Splinter Cell results you suggested the dongle may not be performing as well as it could, despite getting an increase of 97% over the single X1900GT. Seems like it's more a case of the non-dongled version doing well than the dongle doing bad to me.

That's a very good observation, although it somewhat contradicts the argument that 8x8 is a limitation for CrossFire, doesn't it? Problem is, we can't test 16x16 CrossFire on Core 2 right now.

[Rack]

Why not use AMD then? Sure it's a slightly slower platform, but at least the whole basis of the tests is even.

[Steve]

Would we then run into CPU limitations? I expect we could get around it.

Fact of the matter is we tested on Core 2 because that's the processor around which we base much of our high-end testing now. Our results show you the differences with bridged/dongle-less operation on a Core 2 platform. One of the reasons is, as rightfully stated, the PCIe lane issue.

Perhaps a look into the same scenario, but on an AMD platform, is worth a look, but I don't think our Core 2 results are invalid. Still, I take it people would quite like to see how this technology fares with an FX-60 at the helm?

[kalniel]

Sure - would have to crank up the res I guess to put the bottleneck back on the GPU.

It might also answer a question that's been at the back of my mind for a while - is core2duo actually a more efficient processor in terms of the gpus? IE can it make a difference even when the system is supposedly GPU bottlenecked?

[chuckskull]

Seeing as you already have C2D results you'd know straight away if you hit the CPU's limit. Then again GPU speed hasn't really gone up much since the FX-60/62 was king. We're still using the G71/R580. So I doubt you'll have a problem.

[shaithis]

The difference between a Core 2 Duo and a high-end AM2 chip isn't gigantic.

There MAY be a little bottlenecking.....but I am sure you could get a FX62 and overclock it a bit to get close enough