I am about to sell my mining gear, which means I have 4 video cards for sale. 1 x HIS R9-280X
HIS iPower IceQ X² Boost Clock Image: http://i.gyazo.com/2cfedd74454174146836d19154218e1d.png Newegg Link
Reference design. 1 x HIS R9-270X
HIS IceQ X² Boost Image: http://i.gyazo.com/4a8d27da4aeb4e784f12c57252ed51d2.png Newegg Link
Reference design. 2 x PowerColor R9-270X
PowerColor PCS+ AXR9 Image: http://i.gyazo.com/3904ee573f7628cc8e7a07c953da8419.png Newegg Link
Used for mining on a low-power algorithm (x11). Card temps never exceeded 75C during scrypt mining and have been much, much lower most of the time. I ran them in a closed case with dust filters over 4 high-rpm high static pressure radiator fans blowing in from the side panel at full speed, so the video card fans themselves never had to work very hard.
In fact, they're mining x11 right now at full throttle, and here are the temps and fan information: Image: http://i.gyazo.com/d58ff1c2515627c3022dc3f7d12b4d6d.png Image: http://i.gyazo.com/db465627e750aaa258a5fc476be65ff7.png
One of the PowerColors is not mining at the moment because I needed to make room for the 280x.
The PowerColors are voltage-locked but already have a boost clock of 1100Mhz. Memory base clock is 1425MHz.
The HIS 270x voltage is unlocked and has a boost clock of 1050mhz. Memory base clock is 1400Mhz.
The HIS 280x voltage is unlocked and has a boost clock of 1000MHz. memory base clock is 1500.
My overclocking on these cards is limited only to a mining environment and may not have the same capabilities under load from a game, but all three of the 270x cards did 1160/1500 mining, without any voltage changes. I never tried pushing it higher than that, except for the memory. It started to present problems mining scrypt at a mem clock of 1525, but mining on this algo is extremely memory-intensive.
The HIS 280x will overclock well. Did some gaming on it when I had my 7970s. Ran them with the 280x in 3-way crossfire. Ran all three cards at matching specs of 1100/1650 and the 280x did well.
All 4 cards come with original boxes, which will likely cost more to ship. Please keep that in mind when making offers.
I'll entertain serious offers here, and then I'll probably put them on hwswap.