A friend of a friend would sell me his old GTX 660 for 50 Euros and I wonder if it's worth buying. What RAC can I expect with a card like this?

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I would assume between 10 and 12K.

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With each crime and every kindness we birth our future.

Hm, that's pretty much the same as my GTX750. So not worth it. Thx Mike!

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GTX 660 has 960 cores a GTX 75 has 512 cores. 87% more should crunch a fair amount more. I would guess a RAC of 20k or so.

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Anybody here with an active GTX660 who can say for sure?

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I do know my GTX660 crunchs 5 times more on Einstein than my GT 430 did. The GT 430 produces about 4800 RAC on Seti. I don't run the GTX 660 on Seti.

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the 660 definitely has more theoretical output than a 750 but also uses a lot more power

Anybody here with an active GTX660 who can say for sure?

My xw9400 has two GTX 660s (888Mhz and 1110MHz) and two GTX 750Tis (1084Mhz and 1254MHz). That box has only been run sporadically lately so the current RAC is not particularly meaningful, but comparing run times for comparable tasks with similar Angle Ranges on the different cards should provide some useful information. In general, I've found that the GTX 660s crunch roughly 10% more than the GTX 750Tis but, of course, draw more power to do so.

As an example, tasks 4463316415 and 4463316426 both have an AR of 0.709638. The first one ran on the 888MHz GTX 660 and took 15 min 1 sec. The second ran on the 1254MHz GTX 750Ti and took 17 min 46 sec.

You should be able to go through the pending and validated tasks for that box and find many similar examples. By the way, I run 2 tasks per GPU on all cards, since that's optimal for the GTX 750Ti, but the GTX 660s could be just a slight bit more productive running 3 at a time.

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I can give you some numbers:
I crunch about 7hrs per day with 3 CPU threads and the GTX660 (2xMB or 1xAP ... you may get 2xAP and -use_sleep, but with screen lags), which gives me a RAC between 8k and 10k. So as a rough estimate, I guess you'll get around 16k for the GPU only running 24/7. In the old times without creditnew and 24/7 operation I got around 24k with the whole machine.
Also consider the power use compared to the 750. My model (OEM with GK104) uses about 75% TDP for 1xAP at the moment (no additional command line parameters), which means 0.75*130W ~ 98W.

The GTX 660's in my main rig account for 14K each while doing 3 MB tasks at a time but I do not do AP's on them (I leave those for the CPU cores).

Cheers.

Ok, seems like it is a bit faster then, or maybe even more than a bit, but not enough to justify the significantly higher power consumption compared to the 750. Thx everybody!

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I have 3 rigs with GTX660's.

#1 avg. 22,038 credits/per day with AMD 6 core CPU

#2 avg. 19780 credits/per day with Dual Core Intel Pentium

#3 avg. 17980 credits per day with Dual core AMD

Take a look, my computers are not hidden....

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Seti Classic: 204,777 WU /113.636 Yrs

The GTX 660's in my main rig account for 14K each while doing 3 MB tasks at a time

My GTX 750Tis are good for around 11-12,000 running 2 MB at a time (no AP).

The GTX 660 is rated at 140W (GTX 660Ti 150W).
My 750Tis are rated at 60W.
GPU load isn't 100%, actual power used is less than 50W per card.

If I were to put 140W per card in to crunching, I'd go with a GTX970. Not as efficient as a GTX 750Ti, but still better than a GTX 660.

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Grant
Darwin NT

Folks, please consider there are two models of the GTX 660, one with a GK106 and one with a GK104. The specs are thus different, especially the performance for single precision operation, see https://en.wikipedia.org/wiki/List_of_Nvidia_graphics_processing_units#GeForce_600_Series.

I'm running 347.88 on mine, with about 24k average.

Watch the over clocking for crunching, 750's don't like to be clocked much for reliable results.

EDIT: I should say 24k using 4 i5 cores as well.

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Chris anything below 344 seems to be faster checkout team thread Tbars advise or Mark's

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I went to install the new 750 then realised that the Dell PSU is only 300W. I have already upgraded it to a quad core chip, so that was a bit tight. I've just bought an Antec VPF450 450W 80 Plus Bronze PSU that has 2 x 25A on the rails. and only £42. That should do the job!

With your computers hidden I've no idea what your system is, but even the worst of CPUs are generally no more than 130W. A couple of HDDs (depending on age) & 8GB of RAM, 40W (probably less than 30). System fans, Motherboard & wired mouse & keyboard, say 30w (probably closer to 10...). Add on a GTX 750, 55W (due to lack of optimised application actual power use is closer to 45W).
Roughly 255W. So the 300W PSU probably would have been OK, but 400W as a minimum gives a much better buffer.

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Grant
Darwin NT

Oh well.
My old FX 8150 was in the 200 watt range.
Overclocked of course.

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With each crime and every kindness we birth our future.

I went to install the new 750 then realised that the Dell PSU is only 300W. I have already upgraded it to a quad core chip, so that was a bit tight. I've just bought an Antec VPF450 450W 80 Plus Bronze PSU that has 2 x 25A on the rails. and only £42. That should do the job!

Now if your 750 is one that draws all its power through the PCI-e slot Chris you may find that dual rail PSU wanting as you'll just be loading up 1 of those rails (this has been a problem that I've come across many times over the years and changing to a single 12V rail PSU always cures).

If it's 1 of the rare 1's that has its own power connector then you'll be fine.

Cheers.