multi-GPU crunching questions

Sunny129

Diamond Member
Nov 14, 2000
4,823
6
81
although plenty of results came up in my thread search for multi-GPU crunching, i couldn't find definitive answers to my questions:

1) i've seen that folks can run their ATI/AMD cards in Crossfire and their nVidia cards in SLI, but is it possible to run multiple video cards and devote each to their own set of WU's (as opposed to using 2 cards in Xfire or SLI to crunch the same WU or set of WU's)? i figure since neither Xfire nor SLI scales perfectly (for instance, 2 cards in Xfire or SLI do not literally yield twice the performance as a single card), it seems logical that two identical (or very similar) cards, each dedicated to their own sets of WU's, would yield approx. twice the production as a single card, whereas those same 2 cards in Xfire or SLI would yield considerably less than twice the production of a single card.

2) It seems lots of folks have to deal with slow, choppy GUI's when their video cards are hard at work crunching. would it be possible to use my mobo's integrated graphics for display purposes, while using a discrete video card in one of the PCIe slots (though not even hooked up to a monitor) solely for crunching (in an attempt to stave off a slow GUI)?

3) is it possible to have an nVidia card in one PCIe slot (for say crunching E@H or S@H) and an ATI/AMD card in another PCIe slot (for say crunching MW@H)? or am i asking for all sorts of driver issues by attempting this? and for that matter, can i even use two different nVidia cards (for example, a GTX 460 and a GTX 560) or two different ATI/AMD cards (for example, an HD 5870 and an HD 6950)? i don't know if it'll affect the answer to this question, but again i would probably want to run integrated video for display purposes and devote the cards solely to crunching their own projects if possible...

those are all the questions i can think of for now...

TIA,
Eric
 

Rudy Toody

Diamond Member
Sep 30, 2006
4,267
421
126
2) It seems lots of folks have to deal with slow, choppy GUI's when their video cards are hard at work crunching. would it be possible to use my mobo's integrated graphics for display purposes, while using a discrete video card in one of the PCIe slots (though not even hooked up to a monitor) solely for crunching (in an attempt to stave off a slow GUI)?

I am using an ATI onboard video chip for display and NVidia card for crunching.

You need to set your BIOS to point to the onboard display before you install the card.

Some mobos, some GigaByte for example, require the card to also be the display.

Check your mobo documentation for any restrictions about multiple discrete cards in one rig.
 

petrusbroder

Elite Member
Nov 28, 2004
13,343
1,138
126
I have tried different setups for my GPUs and have the following experience:

Q1: I am running - just now on one cruncher only, before on two - two GPUs to one quad core CPU. The GPUs are NVIDIA GTX460 w 1 GByte RAM, both OC'ed. They do not run in SLI. BOINC recognizes both as separate GPUs and I get twice the output compared to one GPU. For some reason i do n ot know some projects are totally OK with this setup (PrimeGrid, DNETC, CollatzC onjecture) and they crunch any combination of WUs. In othjer projects it works well if the GPUs crunch the same project (GPUGRID). But that does not matter, because they switch projects almost simultaneously. So it should work for you.
Q2: Yes, when the monitor is hooked up to the GPU the graphics often get choppier - depends probably on the power of the GPU and CPU. My GTX260s are choppier than my GTX460s, those in my i7-860 CPUs are less choppy than those on my AMD Phenoms
I have set - on a couple of computers - the on-board graphics as the primary one and that works well when both are from NVIDIA or ATI. It does not work well when one of the GPUs from ATI and the other from NVIDIA (no matter which combo: on-board ATI and discrete NVIDIA or on-board NVIDIA and discrete from ATI).
Q3. I have tried that and stopped it. It was a mess with the drivers. I had to uninstall the drivers totally (using driver cleaning software) before I got rid of the problems ...

I did these tests in December 2010 - and the then newest drivers from both GPU-vendors. I have tried it on Win XP Pro SP3 and all tthe updates. BOINC 6.10.58. Projects: Primegrid, Collatz Conjecture, GPUGRID, MilkyWay, DNETC.net, Seti@home (only a few WUs). I had most problems with GigaByte mobos, and none with ASUS and Asrock.
 
Last edited:

Sunny129

Diamond Member
Nov 14, 2000
4,823
6
81
I am using an ATI onboard video chip for display and NVidia card for crunching.

You need to set your BIOS to point to the onboard display before you install the card.

Some mobos, some GigaByte for example, require the card to also be the display.

Check your mobo documentation for any restrictions about multiple discrete cards in one rig.
thank you for the information. at home i've got an ASUS M4A89GTD PRO/USB3 (AMD 890GX chipset) in one rig and an ASUS M4A78T-E (AMD 790GX chipset) in another rig, and both are currently utilizing the integrated video (BIOS is set to use integrated video first). so i just gotta see whether either of these mobos can handle a discrete video card without having to run the display from that card. and i'll check the mobo documentation regarding the use of multiple discrete video cards.

its interesting that you were able to use the ATI onboard video along with a discrete nVidia card without issue, unlike Petrus below, who had issues running either ATI integrated video w/ a discrete nVidia card or nVidia integrated video w/ a discrete ATI/AMD card. i'm assuming that, with the entire crunching load on the discrete GPU and CPU, and all of the integrated video's resources devoted to the display, your GUI isn't choppy at all...is that the case?
 

Sunny129

Diamond Member
Nov 14, 2000
4,823
6
81
I have tried different setups for my GPUs and have the following experience:

Q1: I am running - just now on one cruncher only, before on two - two GPUs to one quad core CPU. The GPUs are NVIDIA GTX460 w 1 GByte RAM, both OC'ed. They do not run in SLI. BOINC recognizes both as separate GPUs and I get twice the output compared to one GPU. For some reason i do n ot know some projects are totally OK with this setup (PrimeGrid, DNETC, CollatzC onjecture) and they crunch any combination of WUs. In othjer projects it works well if the GPUs crunch the same project (GPUGRID). But that does not matter, because they switch projects almost simultaneously. So it should work for you.
Q2: Yes, when the monitor is hooked up to the GPU the graphics often get choppier - depends probably on the power of the GPU and CPU. My GTX260s are choppier than my GTX460s, those in my i7-860 CPUs are less choppy than those on my AMD Phenoms
I have set - on a couple of computers - the on-board graphics as the primary one and that works well when both are from NVIDIA or ATI. It does not work well when one of the GPUs from ATI and the other from NVIDIA (no matter which combo: on-board ATI and discrete NVIDIA or on-board NVIDIA and discrete from ATI).
Q3. I have tried that and stopped it. It was a mess with the drivers. I had to uninstall the drivers totally (using driver cleaning software) before I got rid of the problems ...

I did these tests in December 2010 - and the then newest drivers from both GPU-vendors. I have tried it on Win XP Pro SP3 and all tthe updates. BOINC 6.10.58. Projects: Primegrid, Collatz Conjecture, GPUGRID, MilkyWay, DNETC.net, Seti@home (only a few WUs). I had most problems with GigaByte mobos, and none with ASUS and Asrock.
thank you for the detailed response...you and Rudy are giving me exactly the kind of information i'm looking for. its good to know that, although you had issues mixing ATI/AMD integrated video w/ discrete nVidia cards (and vice versa), you were able to mix ATI/AMd integrated video w/ discrete ATI/AMD cards (and vice versa) without issue. its interesting that Rudy didn't run into problems with this for whatever reasons.

also, could you clarify or be more specific with your response to my 3rd question? in other words, did you try using a discrete nVidia card AND a discrete ATI/AMD card at the same time? or did you try 2 discrete cards of the same make but different models (say a GTX 460 and a GTX 560 together, or an HD5870 and an HD6950 together) at the same time?
 

petrusbroder

Elite Member
Nov 28, 2004
13,343
1,138
126
I tried a Radeon 5850 with a NVIDIA GTX460 - did not work very well - driver issues.
Also the combo of ATI 5830 with GTX285 did not work well - driver issues.
But that was with Win XP. I think that Win 7 would handle this better ...
 

Rudy Toody

Diamond Member
Sep 30, 2006
4,267
421
126
I could not get the NVidia running in a gigabyte mobo and still use the ATI chip for display.

My BioStar mobo handled the same setup without problem. However, the mobo manual said that two NVidia cards could not be done. I don't know about an ATI card in that slot.
 

Sunny129

Diamond Member
Nov 14, 2000
4,823
6
81
I tried a Radeon 5850 with a NVIDIA GTX460 - did not work very well - driver issues.
Also the combo of ATI 5830 with GTX285 did not work well - driver issues.
But that was with Win XP. I think that Win 7 would handle this better ...
got it. so i'd have to test myself to see whether or not 2 different ATI/AMD cards (or 2 different nVidia cards) will work simultaneously. but there's a good possibility that an ATI/AMD video card AND an nVidia video card won't both work in the same machine without driver issues based on your results. although i'm nowhere near ready to jump in and try it, i'm optimistic about running two cards of the same make but different model (for instance a GTX 460 and a GTX 560) since they both run off the same set of unified nVidia drivers...and the same goes for ATI/AMD video cards.


I could not get the NVidia running in a gigabyte mobo and still use the ATI chip for display.

My BioStar mobo handled the same setup without problem. However, the mobo manual said that two NVidia cards could not be done. I don't know about an ATI card in that slot.
Rudy, do you think this was this a result of driver conflicts? or was it due to the limitation of certain mobos only allowing display through a discrete card if one is plugged into a PCIe slot (regardless of the presence of integrated graphics) as you mentioned in your first post?
 

Rudy Toody

Diamond Member
Sep 30, 2006
4,267
421
126
It was the mobo. I gave the card to rabrittain and he put it into the same model gigabyte mobo and had to set it to be the display. No driver conflicts at his end or mine.
 

dajeepster

Golden Member
Apr 15, 2001
1,974
16
81
got it. so i'd have to test myself to see whether or not 2 different ATI/AMD cards (or 2 different nVidia cards) will work simultaneously. but there's a good possibility that an ATI/AMD video card AND an nVidia video card won't both work in the same machine without driver issues based on your results. although i'm nowhere near ready to jump in and try it, i'm optimistic about running two cards of the same make but different model (for instance a GTX 460 and a GTX 560) since they both run off the same set of unified nVidia drivers...and the same goes for ATI/AMD video cards.

Two different ATI/AMD cards will work simultaneously... and 2 different nVidia cards will work also.

I've been doing it all the time.

had gtx280 and gtx 260 working fine together,
gtx 275 and gtx 280 worked fine together

had gtx 480 and gtx 260 work fine, but it depends on the project you are running and if the wu is targeted to a specific card.. i think in gpu grid this matters, but in primegrid and f@h it doesn't matter.

the GTX 460 and GTX560 will work fine together. since they are basically the same.. one is just a "fixed" version of the other.

The thing you need to keep in mind is whether the project you are running is single precision or double precision... at that point it's important that both cards have the same capability.... ie... you can't put a 5770 and a 5870 in a machine and expect it to run milkyway@h flawlessly since the 5770 is only single precision whereas mw@h require double precision... but a 5850 and 5870 works fine together on milkyway@h since both are double precision.
 

Sunny129

Diamond Member
Nov 14, 2000
4,823
6
81
good to know...i think i can manage to keep ATI/AMD cards in one rig and nVidia cards in another (whenever i finally acquire them that is). i'm going to be crunching MW@H for sure, and know to steer clear of the HD 57xx cards haha. in fact, i posted a list of double-precision capable ATI/AMD and nVidia discrete cards HERE in another thread. i'll also be crunching E@H and S@H, and i'll need an nVidia CUDA card for those...though i don't know if they need to be double-precision capable. i'm sure there's a list of compatible cards somewhere to be found. S@H Astropulse i believe has an app now for ATI/AMD cards that i'll also be looking into. i'm not sure if this one will require double precision calculations or not either. but suffice it to say that whatever ATI/AMD card(s) i get, they'll all be double-precision capable.