No one has mentioned the 270's yet. Here's my experience:
Asus R9 270 : Unlocked. 1.100/1030/1400 = 440 kh 7 days stable. 120 W draw per card
Gigabyte R9 270: VOLTAGE LOCKED!
Tried 1.100v and 1.150v in VBE7, flashed BIOS, no errors, but the cards hang on boot when X starts. Running stock, these cards draw 30w more per card than the Asus 270's, for a just a slight 10 kh improvement.
On top of that the Asus cards are quieter and cooler.
Asus R9 270 : Unlocked. 1.100/1030/1400 = 440 kh 7 days stable. 120 W draw per card
Gigabyte R9 270: VOLTAGE LOCKED!
Tried 1.100v and 1.150v in VBE7, flashed BIOS, no errors, but the cards hang on boot when X starts. Running stock, these cards draw 30w more per card than the Asus 270's, for a just a slight 10 kh improvement.On top of that the Asus cards are quieter and cooler.
that's odd. my gigabyte 270's undervolt just fine. i went down to 1.131 using VBE7. They now run 10-15c cooler than stock.
no hanging, no errors. same 480-485KH hashrate, as they did with stock voltage. 1130/1500 tc-15232 -I 19 -g 1 -w 128
btw... someone needs to update VBE7 to run on Win8.1. sucks having to have a win7 VM just to play with GPU BIOS.