Saphire Dual-X R9 280x, getting different results from different cards

[MrGod2U]

About 6 weeks ago I purchased a R9 280x. I spent hours trying to tweak it, and the most I could get out of it was around 550 kh/s. I couldn't remember which make it was exactly, and was too lazy to pull the computer apart to find out. So anyways, went and bought 3x Sapphire Dual-X R9-280x's yesterday. While installing them I noticed that they were the exact same as the card I already had in. When I got it up and running and started mining I was instantly getting around 725 kh/s on two card, the third is only getting 640 kh/s, and the old one is still at 550 kh/s. I'm guessing my first card was defective, and that one of my new ones might be as well. Has anybody else experienced this? Does Anybody know if this is a legitimate reason for an exchange?

[Blowmybarrel]

I would expect to get at least 700 Kh/s per card.

Are they overheating and then throttling?

[MrGod2U]

Well, I wasn't really using my brain too well. The reason the one card is getting around 640kh/s is because it is the card used by the PC for graphics. The other two are dedicated miners. Now, for the first card I had, the original one that was getting 540kh/s, that still seems low, even though it was my only GPU on my desktop. This weekend I plan on mounting all the guts onto a platform and running all 4 of them, see how it performs when it's dedicated.

[Jex_TWO]

Interesting.

I have been mining with my gtx 670 for a while getting about 150 - 180 kh/s , and only recently with the new version on cudaminer i have gotten up to over 250.

I have thought about getting a R9 280X to get better hashing power to increase the gainz
But I'm wondering if this problem that OP has often occurs? Does it happen often that you can get a card that has lower performance than normal?

This weekend I plan on mounting all the guts onto a platform and running all 4 of them, see how it performs when it's dedicated.

I'd really like to get an update to this^, as it would kinda answer my question