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Old 2015-12-05, 08:26   #1
dbaugh
 
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I have a computer with a GTX980. Can I just add another GTX980 and get twice as much TF done on that box? I am not talking about SLI or Crossfire for faster game graphics. Just another honking GPU in an existing box. I know the motherboard and PSU would have to handle it physically and power wise. I have a 580 and use -d 0 and -d 1 to max the card. Will it be something like that to use an additional compute engine? I hope it is easy. Sometimes boxes die but the GPU is still good. I am using Windows.

Last fiddled with by dbaugh on 2015-12-05 at 08:27 Reason: more info
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Old 2015-12-05, 11:04   #2
blip
 
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Just add as many cards as you wish, and your infrastructure permits (slots, PSU, cooling)
Bitcoin miners do this all the time (an arbitrary example here).

Last fiddled with by blip on 2015-12-05 at 11:09
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Old 2015-12-05, 12:24   #3
kladner
 
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Your situation should not be that difficult with 980s. I manage to keep 2 580s relatively happy in one box.

Quote:
I have a 580 and use -d 0 and -d 1 to max the card.
Out of curiosity, what are you running on the 580? It is early for me, and I may not have had enough coffee, yet, but I am confused by the '-d 0 ad -d 1'. In the long past I ran two instances of mfaktc on a single card, but that was with CPU sieving, with a CPU that couldn't keep the card busy with one instance.
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Old 2015-12-05, 19:02   #4
dbaugh
 
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Pleased to hear it is that easy. I run mfaktc on the 580 (two instances).
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Old 2015-12-05, 19:13   #5
blip
 
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Quote:
Originally Posted by dbaugh View Post
Pleased to hear it is that easy. I run mfaktc on the 580 (two instances).
Why do you run two instances of mfaktc on one GPU?
I would understand if you had a 590, since that one has two GPUs...
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Old 2015-12-05, 19:27   #6
dbaugh
 
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Misspoke. It is a 590.
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Old 2015-12-06, 00:58   #7
kladner
 
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Quote:
Originally Posted by dbaugh View Post
Misspoke. It is a 590.
Ah! Thanks! Makes total sense, now.

EDIT: Oooh! Are you talking about putting two 590s in one case? Air cooled? Better look at your case ventilation.

I probably should have mentioned that running two overclocked 580s is with a liquid cooled CPU, and some very noisy case and GPU fans. The GPUs are the "dump heat inside the case" type, not the 'howl while shooting it out the back" type.

Last fiddled with by kladner on 2015-12-06 at 01:03
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Old 2015-12-06, 01:30   #8
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I tried the same with my cards, but always ended up with the PSUs giving up.
Thats why I gave the link in my first post here, where someone tinkered with some cheap Dell server PSUs.
I might do something similar, as it seems to be cheap enough.

But when factoring in (cost of) power usage, it makes much more sense to replace these beasts with e.g. R9 Fury Nano. More GHz/d for less than half the energy. If you buy that card now and calculate 25c per KWh, you will hit break-even after 2 years. (In fact, if you do the calculation more accurately, it will be closer to 1 year, but you get the point).

Last fiddled with by blip on 2015-12-06 at 01:33
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Old 2015-12-07, 11:34   #9
fivemack
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I would be readier to replace my GTX580 with a GTX970 if the GTX970 ran cudalucas at all - all the intermediate residues come out as zeroes when I run cudalucas -d 1.
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Old 2015-12-08, 00:00   #10
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Quote:
Originally Posted by fivemack View Post
I would be readier to replace my GTX580 with a GTX970 if the GTX970 ran cudalucas at all - all the intermediate residues come out as zeroes when I run cudalucas -d 1.
Maybe, but it's superb at factoring - 420 Ghz days/day
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Old 2015-12-08, 00:11   #11
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Quote:
Originally Posted by Gordon View Post
Maybe, but it's superb at factoring - 420 Ghz days/day
Unlike one of my 580s which is currently factoring at a pathetic 505 Ghz days/day, running at 76 C, ATM.
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