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Hi guys, I'm wondering if I should drop another $300 to get a WC'd 5970, and actually use my rad.
I currently run a rig with the following specs:
2x 5970 (1 Water Cooled with an EK Block)
1x 5870
Gigabyte 990FXA-UD7
AMD Sempron 145
Seasonix X-1250W PSU.

Watercool gear:
HWLabs 480 GTX Rad
4x 5400 Gentle Typhoons
XSPC D5 Pump Res Combo

Electricity ain't a problem, so just ignore that. I know that the WC'd 5970 pulls about 84 Amps. (Yes it's overclocked) I overclock all my GPUs. So I was wondering if my PSU could handle another 5970 overclocked?
I have a huge 480 Rad with 4 5400RPM Gentle Typhoons screaming away in my garage, so I want to kind of use my rad, but I'm not sure if my PSU is up to it.

Also I am running Windows 7 64-bit, so could I run 3 5970s and 1 5870, all overclocked, on my PSU, and be able to mine on THEM ALL. I hear some people say that 5 is basically the highest because after that it gets unstable, but others say up to 8 GPUs are fine. I'm confused. :S

Pictures:
http://i45.tinypic.com/10ehlas.png

I have underclocked my WC'd 5970 to get lower VRM temps. I keep all my VRM temps under 100 now. :)

Any help would be greatly appreciated.
Cheers. (Y)

i have a 1200 watt ocz that powers 3 (water cooled) 5970's.   i don't think it's very efficient though (psu gets a bit hot)

seasonic is a lot better.  i think you'd probably have to take out the 5870 though

IIRC, each 5970 will pull about 400W, but that can be lower if you underclock the mem (closer to 325), and even lower if you undervolt (250).

Like zvs said, you would probably have to undervolt, or take out the 5870. I'd go for the former. I know power cost is not an issue for you, but that would still net you the most MH/s.

this might help
4 air cooled 5970's  at stock volt will pull 1250 watts at the wall.

4x 800/300/1.05v 1245w 2900Mh

what is even better is at 0.95v

4x 675/300/0.95v  835w  2470Mh


do the math, you make more money when you undervolt.

well, it depends on how much your electricity costs

last year mine was around 10c, but this year it's ranged from 7.5c-8c (variable).

i have 5 5970's, i run 7 of the GPUs at 815-150, one at 810-150, one at 780-150 (it blows), and another at 0/0 cause it has something funky going on...

anyway, they're all in that stage between >1v and <1.05v (i set it to 1.01v but i guess it's all the same).     at 1.05v, 2 of the GPUs are stable at 850, one at 845, one at 840 and the rest are all 830 or lower, so not really worth it.    i have to drop a bunch to get them stable at 0.95v.  for >0.95v to <1v  they are stable between 730-740

That's true. At 0.95, my 5870 is only stable at 740. I bump it to 1.000, and it goes up to 925. Even at 14c/KW, it's more profitable to NOT undervolt as low as it can go. I go to 0.95 with my 5970s for heat management/VRM temps/lower fan speed/prolong their life, however.

If ya glue another pcie slot to your motherboard you might be able too =p

My mobo can fit 4 cards.
Straight off the Gigabyte website, on the page of my MOBO.

http://www.gigabyte.us/fileupload/product/2/3880/4378.jpg

Ohh and also, the board layout.
http://www.gigabyte.us/fileupload/product/2/3880/4376.jpg

6 PCI-e slots. I think so.

Great mobo, to bad it's running a cheapo Sempron.

well, i have dual core CPU's in all of my machines, but just because that's what i had leftover from years ago.  

i disable one core, underclock mb, turn off sound and all that junk.

I guess we can close this thread.

Answered my question, just got another WC'd 5970 in my Rig.

2x 5970's WC'd.
1x 5970 on Air.
1x 5870 on Air.

All happy hashing away at 2.9 GHash/s. Could overclock more to get to 3 GHash/s, but I like all my temps below 90, besides the 5970 on air. :S

PSU is Seasonic X-1250

http://i49.tinypic.com/1epbmt.png

Could i fit 3x 5970's back to back in a motherboard on test bench or would this make too much of a heat problem? they pull air from the front and exhaust out the back it looks like