Hi, will crunching work efficiently with 2 x 295's?

I am planning a new machine, but don't know much about sli/gpugrid/vista/ubuntu.

I am thinking about 2 GTX295's if they can be fully utilsed for gpugrid under ubuntu (I read thats the more efficient OS), but then also want to have it as a dualboot vista for games. Would this work?

Would I need to change SLI connectors? The 4 card machine as an example picture on the Gpugrid site doesn't apppear to have sli connectors between the cards?

Thanks,
Far

2x295's will run 4 GPU workunits at a time. Since these workunits are fed by number of CPUs, you will need a Quad or more to keep them from being idle.

Due to it not being supported (yet) in CUDA by NVIDIA, GPUGRID applications will treat cards in SLI as a single card and only run on one of them.

I would consider running just your Vista OS. Ubuntu is alittle faster than Vista, I run linux for dedicated crunchers, but not for machines I use.

I wouldnt even bother running the cards in SLI, most if not all games right now can barely benefit from SLI, especially with 295's, where games struggle to even use both GPUs on one card.

The second 295 would basically be just for crunching.

I use a 280 in my gaming machine, and I cannot find a game that cripples this card. Most games, incuding Crysis/Far Cry 2 can run at 19x12 & maxed out settings. I can only imagine what a 295 can do.

Switching back and forth from linux to windows for the sole purpose of crunching seems like a waste, you'll end up spending most your time in windows when your on it. I just suspend work when I game, and resume when Im done. It is much easier then dual booting.

Linux was supperior when it could run CPU + GPU tasks without loosing cores, but windows can do that now also. With the update to the app GPU tasks use little CPU power, between 3-5% per task on my machines (with Q6600's)

I have a similar setup (dual 295's, amd9950) running under Fedora 10. The linux drivers don't seem to control the fans properly (or at all). There were numerous client compute errors until I set the card fans to 100% duty cycle with nvclock (this may be overkill). Haven't seen a single client error after this change.

Curt

Another thing about SLI. You do not need to remove the physical connector on the cards. Leave them on. Then you can simply enable SLI in the nVidia control panel when you want to play games (if you even need more graphics power), then disable it in the control panel again when you return to CUDA processing. It's just a simple checkbox in the control panel and a real time change so no booting or anything needed. But, like a previous post said, even hard core games like Crysis with all settings maxed won't phase a single GTX 295, so most likely for now like they said, just leave SLI disabled. I'd go ahead and install the SLI connector anyway just so you don't lose it and have it in place in case you use it down the road.

If you are going to enable and disable SLI though, I would suggest fully exiting BOINC and the science apps before each SLI change, then just start it back up again a few seconds later after you've made the change. That way, BOINC can detect on startup how many CUDA devices you have available. Again, if SLI is enabled when BOINC starts, it will see all the video cards in SLI as one single device, so that's why you need to have it disabled BEFORE you start BOINC. Also, I haven't tested it, so I don't know how BOINC would behave if you have multiple WU's in progress, then you reduce the number of CUDA devices and resume work. Now it sees less GPU's available, so not sure if it would simply suspend it, or abort it, or what.

Like they said, it would probably be easiest to just leave SLI off all the time since you probably don't really notice any significant benefit, even in games, on any of the GTX boards. Sure, a benchmark program may detect a few extra frames or something, but you won't notice that visually. Older boards might make more difference, but all of the GTX 200 series boards are so fast, I've maxed out every setting on every game I run and never noticed an issue with SLI off, and I'm running the GTX 260 boards which are the slowest in this new line, so I wouldn't think games will be an issue.

Now... if I forget to suspend BOINC when I start a game.... lol... that I notice!

Thanks so much for all the information, assistance and suggestions.

The machine will be my first dedicated cruncher, but then I thought it's specs are surely going to be wasted if I don't play a game on it also :-) So I'll make it ubuntu just for the minor increase in points when crunching, and slap vista on it just for a quick runthru on crysis. The monitors 25x16 I'm not sure even this setup will handle full maxxed out settings but it will be fun to see.

I'll put the sli connectors on as suggested, but won't enable sli in the drivers when crunching, and will exit boinc when changing the settings.

It's all coming together planwise - you guys have given me all the info I needed re setup for graphics (will just get the cheap Palin ones), so now waiting on release of:
- the D0 stepping revision for the i7 920
- the asus ROG Gene mobo (so I can fit it all in a mini P180)
- the enermax revolution 1000 or 1250 psu to get to australia (>85% efficiency)

Then onwards. Thanks,
Far

The P180/182's are excellent cases - the easily cleanable dust filters are priceless. But am out of space, so I have to see how much crunching effort can be fitted into a mid-tower area. The case appears great quality however possibly may require some minor case mods to fit power cabling in as well as both GPU's.

Geez this took forever to get the dosh together, the parts to get the australia, and then to get it running! But finally it's stable, and gotta say it looks so neat it's a shame the inside isn't on the outside! The black interior to the case looked so tidy, I couldn't help spending 5 mins spray painting the few things that weren't black to also be black! That's the DVD drive, back panel plus an ice cream container I cut up to help duct the heat out from the GPU's. Shame the fans I replaced with noctua oil/magnetic bearings ones aren't black also.

Fingers crossed it finds some protein designs and failing that I'll have fun playing games on it :-)

Crunch on!