I know some info on this has been in the threads here, but I just can't find it.

I'm thinking of buying a 2GB GTX 680 (God bless Craigslist!) and I'd like to know what is the max number of WUs one can run at the same time. Or, to put it another way, at what point does the card max out in terms of GPU usage?

More precisely, I'm thinking (for energy saving reasons) replacing a pair of GTX 460s (not OC) running 2 WUs at a time each. So what I really want to know is: can the GTX 680 outwork the pair of GTX 460s? Or at least, be their equal in terms of RAC?

Thanks all for your help!

---

I know some info on this has been in the threads here, but I just can't find it.

I'm thinking of buying a 2GB GTX 680 (God bless Craigslist!) and I'd like to know what is the max number of WUs one can run at the same time. Or, to put it another way, at what point does the card max out in terms of GPU usage?

More precisely, I'm thinking (for energy saving reasons) replacing a pair of GTX 460s (not OC) running 2 WUs at a time each. So what I really want to know is: can the GTX 680 outwork the pair of GTX 460s? Or at least, be their equal in terms of RAC?

Thanks all for your help!

Looking at your machines, could not see which one you are talking about, but if it is the Intel machine, you might be able to increase the count to 3 tasks (<count>.33</count>) w/o any problems. I have been running a GTX460SE/1Gb with 3 tasks for the last several days. Was running with 2 until I installed a GTX660SC/2Gb and experimented with running 3. Tasks might take a little longer to run, but I've found that mine are runnning about 9-15 min with 99% usage. depending on the size of the task. I'm also running BOINC 7.0.42/_x41zb(Cuda 4.2). Some people seem to have a problem with heat, but I've found that not to be an issue as the card runs between 50-60c depending on room temps. If you should decide to get the GTX680s you could run with 3 maybe 4 at a time.

---

I don't buy computers, I build them!!

@Cliff - Thanks for the response.

The Intel machine has only 1 GTX 460 with 1GB, the other is 768MB, so less room, if only because BOINC can't tune itself and uses an all-cards-are-the-same philosophy ((yeah, I know it would be difficult, if not impossible, to do)).

Even so, 3 will fit on the 460s, but when I tried it awhile ago, it seemed that 2 -> 3 gained negligible RAC because the card was at 95+% usage with 2, so no gain with 3. The WUs just took 50% longer than with 2.

You nailed it - I am hoping to run 4 on a 680; that's what I was asking about. No answer so far, though.

---

3 WU are optimal for GTX 680.

---

for what it is worth, I run 2 at a time on my 680. It could handle 3 but the improvement is surprisingly small if any, and the utility of the computer declines badly.

As always your mileage may vary.

---

Janice

Actually, what I am trying to find out is if, for crunching purposes, 1 x GTX 680 >= 2 x GTX 460. Considering the 680 running flat out will draw around 100 watts less than the 2 x 460, and my electric rates in Boston (~ 15cts/kwh) I figure that should save me $100/year, conservatively calculated. That's my goal here.

---

I dont have a precise answer, but I can give you some data...

My GTX680 set at maximun TDP without OC gives me around 25K RAC on SETI, but Im pretty sure the RAC its beeing limited by the recent issues of the project...

On tests Ive made on Einstein, the gtx680 = 1.5 560Ti, Im not sure how much slower is a 460, but it should be a 25% slower than the 560TI to get the same performace of 2 460s with just 1 680...
(NOTE: your mileage may vary, my guesses can be wrong, and my GPUs seem to be always slower than anybody else's GPUs no matter what :S )

---

I have the same experience as Horacio.

The 560Ti does roughly 25k as well as the 680.
The 580 is a bit faster but not much.

---