Advice from someone who isn't a moron

[FatMagic]

What I mean is that undervolting increase efficiency, but (past a certain value) not necessarily increase profit.
You should try undervolting, but use something like http://dev.bitcoinx.com/profit or http://dustcoin.com/mining to calculate the actual profit.
A Killawat shoud help you very well.

Just purchased a Kill-a-Watt today with the two 7950's I purchased
So yes, I will be trying this for sure.

[Dargo]

If 7950s are already undervolted to 1.09 VDC, and you undervolt the 5950s to similar or lower, the PC P&C will handle that no prob. But trying to optimize given your electricity costs probably a good idea. Going by hazy memory, I think my 5850s only got about 325 Mh/s mining BTC @1.05 VDC, as opposed to around 310 Mh/s @ 0.95 VDC, and the % diff in power draw was significantly more, so the extra 0.1 VDC wasn't worth it in my case.  

Edit: BTW, you sure you can run 79xx and 59xx together? I seem to recall people having a problem with this.

[crazyates]

Undervolting will undoubtedly help your PSU handle all those GPUs, but it might not increase profitability. Remember, efficiency and profitability are NOT the same. Here's a quick chart that I keep up to date with my 7970. It's not exact, but I adjust the PPS rates and the USD/BTC whenever I want to look at what setting is most profitable. I used to make more money undervolting, but with the massive increase in price, it's better to just flat out overclock and mine as many BTC as I can.

[crazyates]

Undervolting will undoubtedly help your PSU handle all those GPUs, but it might not increase profitability. Remember, efficiency and profitability are NOT the same. Here's a quick chart that I keep up to date with my 7970. It's not exact, but I adjust the PPS rates and the USD/BTC whenever I want to look at what setting is most profitable. I used to make more money undervolting, but with the massive increase in price, it's better to just flat out overclock and mine as many BTC as I can.

Woops forgot to include the chart. Click for bigger version.

[FatMagic]

Edit: BTW, you sure you can run 79xx and 59xx together? I seem to recall people having a problem with this.

Well we are surely going to find out - hah! If not, oh well. I have a 2nd rig I could fire up and run the other two. Or, sell the 5850's and invest in another 7950. If you find any additional information about the potential incompatibility, let me know. Thanks

Woops forgot to include the chart. Click for bigger version.

Yes, good idea. It may be more profitable to run them at full power, or overclocked and make more BTC/LTC. Your chart is phenomenal! Any chance I could get a copy of this spreadsheet? I'd like to use it for BTC, and then modify it for LTC. I love having all the numbers at my fingertips... (and I like to have provable numbers I can show my "accountant").

[philips]

The recent BTC price surely is helping, but not by much, at least is not helping me (with a mix of 7xxx + 5xxx cards @ 0.16 power cost).

Normal volting: 5290 Mh/s @ 2174W = 28.18 USD/day  (E = 2.43 MH/s/W,  Temps @ 67, Fans @ 80%) (7xxx@1.17V, 5xxx@1.2V)
Undervolting   : 4930 Mh/s @ 1700W = 27.51 USD/day  (E = 2.90 MH/s/W,  Temps @ 59, Fans @ 50%) (7xxx@1.09V, 5xxx@1.062V)

For 7xxx cards only (specifically 4 x 7970):

Normal volting (1.17V): 2800 Mh/s @ 1170W = 14.84 USD/day (E = 2.39 MH/s/W)
Undervolting    (1.09V): 2545 Mh/s @   788W = 14.55 USD/day (E = 3.23 MH/s/W)


Pros and cons

[FatMagic]

The recent BTC price surely is helping, but not by much, at least is not helping me (with a mix of 7xxx + 5xxx cards @ 0.16 power cost).

Normal volting: 5290 Mh/s @ 2174W = 28.18 USD/day  (E = 2.43 MH/s/W,  Temps @ 67, Fans @ 80%) (7xxx@1.17V, 5xxx@1.2V)
Undervolting   : 4930 Mh/s @ 1700W = 27.51 USD/day  (E = 2.90 MH/s/W,  Temps @ 59, Fans @ 50%) (7xxx@1.09V, 5xxx@1.062V)

For 7xxx cards only (specifically 4 x 7970):

Normal volting (1.17V): 2800 Mh/s @ 1170W = 14.84 USD/day (E = 2.39 MH/s/W)
Undervolting    (1.09V): 2545 Mh/s @   788W = 14.55 USD/day (E = 3.23 MH/s/W)


Pros and cons

Good information. Is that just a single rig? How many cards total on that?

[philips]

Two rigs.

6 x 5870 > first rig,
4 x 7970 > second one.

[crazyates]

Woops forgot to include the chart. Click for bigger version.

Your chart is phenomenal! Any chance I could get a copy of this spreadsheet? I'd like to use it for BTC, and then modify it for LTC. I love having all the numbers at my fingertips... (and I like to have provable numbers I can show my "accountant").

Ya I included all of my maths in the bottom row so anyone can replicate it. Just do some testing with you hashrate and power draw, and plug them into excel.

[FatMagic]

Woops forgot to include the chart. Click for bigger version.

Your chart is phenomenal! Any chance I could get a copy of this spreadsheet? I'd like to use it for BTC, and then modify it for LTC. I love having all the numbers at my fingertips... (and I like to have provable numbers I can show my "accountant").

Ya I included all of my maths in the bottom row so anyone can replicate it. Just do some testing with you hashrate and power draw, and plug them into excel.

Derp derp I didn't see that - thank you

[zenid]

You can obviously modify this design with whatever GPU's you want. The 7950's are particularly good at hashing for LTC, I'm not sure about their ability to hash BTC.

This chart offers benchmarks, though I can't vouch for them:

http://media.bestofmicro.com/G/Y/355714/original/0101%20Bitmining.png

[alexeft]

Edit: BTW, you sure you can run 79xx and 59xx together? I seem to recall people having a problem with this.

That's what I'm doing. It works just fine with cgminer.

[FatMagic]

Edit: BTW, you sure you can run 79xx and 59xx together? I seem to recall people having a problem with this.

That's what I'm doing. It works just fine with cgminer.

Cool! Thanks for this

[drewz]

Hello all,

I want to place an order on this setup what do you think ? no open case available in my are.

..and i plan o mining litecoin

CPU: AMD - Procesor AMD Athlon II X2 Dual Core 250 (C3) (BOX)
MotherBoard: GIGABYTE 990FXA-UD5, AMD 990FX + SB950, AM3+, DDR III, USB 3.0, PCI-E 16x, SATA III
PSU: Antec HCP-850, 850W, Modulara, Vent. 135mm, Efficiency 92% (80 PLUS GOLD)
Ram: Corsair Vengeance DDR3, 2x4GB, 1600Mhz (Dual Channel)
Case: CoolerMaster - Carcasa CoolerMaster HAF 932 Advanced
Hdd: some old suff i found at home
Video Card:3 x Sapphire Radeon HD 7950 Boost, 3GB, GDDR5, 384bit, DVI, HDMI, Mini-DisplayPort, PCI-E 3.0

[shep80]

Hello all,

I want to place an order on this setup what do you think ? no open case available in my are.

..and i plan o mining litecoin

CPU: AMD - Procesor AMD Athlon II X2 Dual Core 250 (C3) (BOX)
MotherBoard: GIGABYTE 990FXA-UD5, AMD 990FX + SB950, AM3+, DDR III, USB 3.0, PCI-E 16x, SATA III
PSU: Antec HCP-850, 850W, Modulara, Vent. 135mm, Efficiency 92% (80 PLUS GOLD)
Ram: Corsair Vengeance DDR3, 2x4GB, 1600Mhz (Dual Channel)
Case: CoolerMaster - Carcasa CoolerMaster HAF 932 Advanced
Hdd: some old suff i found at home
Video Card:3 x Sapphire Radeon HD 7950 Boost, 3GB, GDDR5, 384bit, DVI, HDMI, Mini-DisplayPort, PCI-E 3.0

I would recommend a larger power supply for 3x7950's... Would suggest a 1000 - 1250 w of a good brand.