AMD's CrossFireX: Tri & Quad GPU Preview
by Anand Lal Shimpi on February 21, 2008 3:00 AM EST- Posted in
- GPUs
The Drivers
Make no mistake, we are dealing with the earliest drivers AMD was willing to let out of its control - in other words we should expect bugs.
Much like our Radeon HD 3870 X2 experience, CrossFireX just worked. Switching between 2, 3 and 4 GPUs did require a driver reinstall for things to work perfectly but once we ticked that little CrossFire checkbox everything worked as it should.
CrossFireX: Don't Feed After Midnight
The rules for CrossFireX are simple: you can make any combination of up to 4 RV670 based GPUs, using either Radeon HD 3850s, 3870s or 3870 X2s. Note that the upper limit is two Radeon HD 3870 X2 cards (4 GPUs).
While the clock speeds aren't normalized to the slowest card in the arrangement, the faster cards will have to wait on slower cards so ideally you'd want to pair similarly clocked GPUs.
Two Radeon HD 3870 X2s in action
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PhantomKnight - Thursday, February 21, 2008 - link
Sorry getting used to the comment posting.This would have helped.
3 x Radeon HD 3870 (2 X2 + 1)
NicePants42 - Thursday, February 21, 2008 - link
I was also wondering what that meant. Looks like two 3870x2s plus one 3870.I was also a little confused about the system setup - looks like they were using nVidia hardware and drivers...
tynopik - Thursday, February 21, 2008 - link
obviously it's a typo and they meant 1 X2 + 1PhantomKnight - Thursday, February 21, 2008 - link
Am I alone in being confused, i thought that 2 times 2 plus 1 is equal to 5.Anonymous Freak - Thursday, February 21, 2008 - link
Previous 3870 CrossFire vs. 3870X2 reviews have shown that the X2 performs better than two standalone 3870s in CrossFire. So using "2 GPUs" as the X2 only might be deceptive. I want to see:One 3870
Two 3870s
Three 3870s
One 3870X2
One 3870X2 + one 3870
Two 3870X2s
(I don't think there is any board that could take four plain 3870s.)
Simply because from previous reviews, the "one to two" delta is much higher for X2 than for two plain 3870s. Another question is if the delta from one to two 3870s is the same as one to two 3870X2s. Based on previous X2 reviews, it looks like by all rights, the system really sees the X2 as a single double-fast GPU.
Goty - Thursday, February 21, 2008 - link
The MSI K9A2 Platinum can. =)Actually, I think that's the same motherboard used in this review.
Anonymous Freak - Tuesday, February 26, 2008 - link
Except when you use all four slots, they all drop to x8. And, yes, you would need a case with 8 back-panel slots, including one beyond the 'bottom' of the card. (Or you'd need to hack your cards to be single-slot.)strikeback03 - Friday, February 22, 2008 - link
How many cases have the openings on the back for 4 dual-slot cards?yyrkoon - Thursday, February 21, 2008 - link
"From AMD's explanation it sounds like there's still a lot of work to be done on the CrossFireX driver. While we can expect to see its public debut in March, it seems like it'll be a while before we're anywhere close to ideal scaling. We've found ourselves in this position with many-GPU designs in the past, at least the players are taking things a bit more seriously this time around."You guys, and many others have been talking about how well quad core CPUs scale(or dont) in a none server, are you really all that surprised to find that quad GPUs would be similar ?
I have been long suspecting that while the PCIe specification is absolute in how much bandwidth a number of PCIe lanes are supposed to have total, that motherboard manufacturers have been skimping as to how much they are allowing those lanes use. Maybe this is just now biting them in the behind ? Or maybe I am just being silly . . . ; ) Either way, system details are not exactly forthcoming here.
skiboysteve - Thursday, February 21, 2008 - link
... What?