CrossFireX Arrives: First Look at 3 and 4 GPUs in 2 Card Setups
by Derek Wilson on March 7, 2008 12:05 PM EST- Posted in
- GPUs
… and Tearing it Down
Whether the problems we saw end up being very isolated problems or not, it's always good to be cautious. Now, let's move on to the part that will absolutely affect everyone who runs CrossFireX at some point: uninstalling the hardware. Until now, if we needed to step down to one card all we needed to do was remove the hardware and everything would be fine. AMD tells us that because CrossFireX uses Windows Vista's Linked Display Adapter (LDA) technique for combining multiple physical graphics cards into one virtual device, this is no longer as simple.
Before removing a card from the system, you MUST disable CrossFireX or uninstall the driver. If you do not disable CrossFireX, the driver will fail to load the next time the system boots. There will be no way (from what we can tell) to disable CrossFireX if the driver doesn't load. Thus, the driver will need to be uninstalled anyway. If you want to keep one card in the system, be sure to disable CrossFireX first or you will have to uninstall and reinstall your driver.
We've asked for more details about why this isn't something AMD can handle in the driver, and this is what we understand so far. After LDA mode is set up, a specific number of physical devices are expected when the driver tries to load. If there is only one card present, this looks the same as if the link failed and thus the driver won't load. AMD has said that this is the expected behavior based on how Vista handles LDA. Our position is that if this is the case, it is a design flaw in Vista that Microsoft needs to address.
After speaking with AMD on this, they have said they would try to make the documentation about how to handle uninstalling hardware properly as prominent as possible. While it's not ideal, thorough documentation of the issues is definitely a good thing to have when potential issues are very likely to arise.
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mmntech - Saturday, March 8, 2008 - link
I'm running an HD 3850 256mb and I get 40fps average in low density areas, 12.4fps in London. Ultra quality of course with no AA and in game AF at 1440x900. That's DirectX 9.0 performance, which is all I could test since I don't run Vista. Flight Simulator has always been very CPU dependent, particularly concerning autogen scenery, and AI traffic along with the complex physics engine. Since FSX with SP1 can take advantage of up to four CPU cores, it might be worth starting off there. I did my tests using an Athlon 64 X2 3800+, everything at stock speeds with 2gb PC3200. If I were you, I'd go with the single 3870 X2 card. Cheaper than buying two separate 3870s. For nVidia, maybe two 8800GTS 640mb cards in SLI or better if you want the best performance. I'd wait for nVidia to release the 9800GX2 first though to see what cards offer the best performance per dollar.As for the article, I really wonder if using more than two cards is really practical. You can get almost the same performance with two 9600GTs as with three or four HD 3750s but the two 9600GTs are far cheaper. This begs the question, is spending the extra $400 really worth it for such minimal gains? I know for some it is but then why buy mid-range cards when a couple 8800GTXs will cost the same in the end. Plus there's also the increased heat and power consumption from using four cards instead of two. I'd like to see more info on that.
Incisal flyer - Monday, March 10, 2008 - link
Thanks for the replies derek anm mmntech. Mmntech, yes my feelings exactly about quad (basically) crossfire. I'm no computer geek (more like a newbie really - I don't understand understand most of what I read in the forums and couldn't overclock a toaster if you held my mother hostage). Multiple crossfire sounds just too exotic at this point and would be more headache than it is worth. Thanks for your feedback and happy flying.The Flyer
DerekWilson - Saturday, March 8, 2008 - link
i'm looking at fsx acceleration for future graphics articles ...no promises, but i've been testing it internally.
Sundox - Saturday, March 8, 2008 - link
isn't multi GPU the cheap way to go?I'm asking this because I can't figure a car race won by two slower cars, against the faster car, or two knifes cutting my steak smoother.
to me, it looks like the problem is,... coping with the problem, the companies just want to have the most powerful GPU, not the most efficiant.
I might be totaly wrong.
coldpower27 - Saturday, March 8, 2008 - link
It's more like a delivery race rather then a car race, who can deliver the total shipment fastest?Two smaller trucks pulling half the load each, or a single truck pulling a larger load, the larger truck's engine is more complex, and hence more difficult to build, vs the smaller trucks which have smaller engines which are easier.
Griswold - Saturday, March 8, 2008 - link
Analogies like that do not always work just like that.Besides that, the car race example isnt that simple anyhow. Imagine a 24h race which could easily be won by even one slower car, as long as it is more reliable than the faster one. Remember, in order to finish first, one must first finish. This, of course, has little to nothing to do with video cards, hence, analogies dont always work.
legoman666 - Saturday, March 8, 2008 - link
analogies almost never work.DerekWilson - Saturday, March 8, 2008 - link
"Like a balloon, and... something bad happens!"Simon128D - Saturday, March 8, 2008 - link
I love the reviews and benchmarks here, I really do but I'm getting sick and tired of seeing the test system being only a super high end machine with hardware that the average person can't afford and I think benchmarking with skull trail on its own is silly. Tis applies to other site as well.Don't get me wrong, I enjoy seeing benchmarks from a high end system like skull trail but how many people actually have or can afford a system like that. I'd like to see more of a mid range setup inculded in graphics benchmarks - that will give a more realistic view point. A system say with a 780i or X38 chipset with a Q6600 and 4GB DDR2 800Mhz etc.
Just my thoughts.
DigitalFreak - Saturday, March 8, 2008 - link
It's really the only way to make sure the games they're testing with aren't CPU limited.