The last couple of posts in this thread have been talking about mining with efficiency (ie. You pay ~10c/kwh).
5970, linux amd64, cat 11.12, sdk2.5
cgminer @ 0.95V/600/150, 273W, 542Mh/s
7970, windows 7, cat 11.12 7970 edition, sdk 2.6
phoenix @ 0.92V/925/150, 217W, 535Mh/s
1) It doesn't make economical sense to undervolt (at this time) given the price of Bitcoins. I make more at full clock full voltage than I do undervolting.
2) 5970 can go much higher than 600 Mhz @ 0.95V. I have test 680 Mhz @ 0.95V and 750 Mhz @ 1.0v. But as I said above it actuall results in LESS net revenue (after electrical cost) to undervolt.
4x5970 rig
820/300 @ 1.05V
3.2 GH/s
1050 W (at the wall)
Daily revenue gross = $10.50 (current price/difficulty)
Electrical cost = -$2.50 (@ $0.10 per kWh)
Net Revenue = ~$8.00
4x5970 rig
680/300 @ 0.95V
2.6 GH/s
840W (at the wall)
Daily revenue gross = $8.50 (current price/difficulty)
Electrical cost = -$2.00 (@ $0.10 per kWh)
Net Revenue = ~$6.50
So yes undervolting does reduce electrical costs but it loses more in gross revenue.
Save $0.50 in electrical card per rig per day but lose $2.00 in gross revenue per rig per day.
Even if we assume 30% overhead due to AC cost it is still less profitable to undervolt.