Re: Official R9 Graphics Card Voltage Locked/Unlocked list
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.
Gigabyte R9 270: Modable with VBE7 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.I'm running 2 at 1.043V and hashing at 475 Kh/s and 445 Kh/s on W7 and Catalyst 13.12 without any issues. Hanging on boot on your rig or OS installation is no evidence whatsoever that they are voltage locked. Perhaps you forgot to set also a lower clock speed on VBE7