Stop mining and undervolt your cards with VBE7 http://www.techpowerup.com/forums/threads/vbe7-vbios-editor-for-radeon-hd-7000-series-cards.189089/

Also, increase the fan speed.

"gpu-fan" : "70-100",
"temp-target" : "70",
"temp-overheat" : "75",
"temp-cutoff" : "80",

If you feel like it, maybe replace the thermal paste on that card.

Are those cards too close and you aren't using a riser? You need a large fan, then.

You can't mine like that, way too hot. See if Gpu-Z or HwInfo64 sensors show the other temperatures.

Instead of flashing a 6950 to 6970, use the original 6950 BIOS and use RBE to unlock the shaders.
http://www.techpowerup.com/downloads/1962/techpowerup-radeon-bios-editor-v1-28/

This allows you to increase hashrate but at the lower voltage that the 6950 can withstand. Otherwise funny things can happen like overheating, throttling and killing the card soon. Also, perhaps your riser isn't that good.

After flashing the unlocked 1.1V BIOS, put the 6950 on the PCI-e 16x slot and see if it hashes fine.

You shouldn't use -g 1 with my config. Either use -g 2 or use
vertminer.exe  -g 1 --failover-only
on the command line

and
"gpu-threads" : "2",
in the config

Gigabyte R9-270 OC: 230 Kh/s

"intensity" : "13",
"gpu-threads" : "2",
"worksize" : "256",
"lookup-gap" : "2",
"thread-concurrency" : "6720",
"shaders" : "1280",
"gpu-engine" : "1080",
"gpu-memclock" : "1500",

I've seen people reporting good results with ASUS and Gigabyte 280x.

I have VTX3D 7970 and 280x (managed to get them at 235 and 218€). They are decent for a budget brand, even if the voltage oscillates and don't allow for very agressive undervolting and power savings. IIRC I get 760 Kh/s at 1060 Mhz core, 1600 Mhz vram and 1.081V after BIOS mod and sgminer, but I'm not mining scrypt atm

The XFX are shunned by coin miners for giving low hash rate and using low quality components. Not sure how this particular model will behave.

I've read some MSI are voltage locked.

You have to undervolt and otherwise tweak your cards with custom bios, bin files and miner software, for most hash rate OR best efficiency (depending on how much you pay for power in your region), so perhaps those 2 cards are bad options. But then, I'm talking a bit out of my ass because I don't have them.  

You are the dude that wants to get 18 cards, right? Perhaps you should order 1 XFX and 1 MSI upfront to test, and then grab the one that gives best results.


Check these 2 important threads:
Speed:
https://litecointalk.org/index.php?topic=15902 (locked now)
https://litecointalk.org/index.php?topic=14996

Power efficiency:
https://bitcointalk.org/index.php?topic=395004.0

Excellent pool operator! 

I'm waiting for those 860 and 870's too, but nobody forces me to max out my ATI cards hashrate, supply whatever voltage that speed requires, and then complain it is not power efficient.

Someone managed to pull  3.8 Kh /W at 0.9V out of a XFX 7970, I'm following his progress.

Maybe because either "gpu-memclock" is too high or the VRMs are at absurd temperatures.

Use gpu-z "sensors" to check the latter, while mining.

"intensity" : "19",
"lookup-gap" : "2",
"thread-concurrency" : "21712",
"gpu-threads" : "1",
"gpu-engine" : "1000",
"gpu-fan" : "60-90",
"gpu-memclock" : "1500",
"temp-cutoff" : "80",
"temp-overheat" : "75",
"temp-target" : "68",

Perhaps the massive # of calls per second to the driver trigger an internal bug, if you use high intensity with so many cards. Nice that you solved it with -I 19. Keep it, you will probably get higher Work Utility and less stales anyway.

IDIOT, NOBODY CARES. GET LOST!

Edit: Oops, Saturday night, a few drinks, hehehe  

You can always parse http://poolpicker.eu/text.php, but that does not mean it works well in practice. There's a cost from switching, you need to consider unexchanged balance, your ping to those pools is certainly different, past performance doesn't guarantee the future, etc...

r0ach is a concern troll, also a dev of other coin. Nothing new here

That does not mean one should blindly follow this journal. I don't want to buy an over-valued coin based on the hype, that others will dump on me for the quick buck. But this thread is by far one of the best I can find here at btctalk, regarding learning and investment tips.

Oh, good point! How much power is it then with -H 2, with the card overclocked and not?

These 2 reviews contradict themselves:

http://www.pcper.com/news/General-Tech/NVIDIA-Coin-Mining-Performance-Increases-Maxwell-and-GTX-750-Ti

http://www.extremetech.com/gaming/176785-nvidias-new-maxwell-powered-gtx-750-ti-is-hyper-efficient-quiet-a-serious-threat-to-amd/3


Also, look at https://bitcointalk.org/index.php?topic=395004

I'm yet to see evidence of this

Maybe, but you will be pushing it. Seasonic X are very good, so there is hope.

Make sure you seriously undervolt your 280x, also your CPU on the BIOS and use power save settings on the GTX670. See drakoin's thread on undervolting and power saving.

If you have a watt meter, see how much you pull from the wall while mining and gaming. Up to 650W and occasionally a bit more is fine.

So we're talking about 100+W at hashing?

Please post your config and a screenshot of Gpu-z "Sensors" tab of that card, while mining.

After you buy a new graphics card, you only need to download and install suitable drivers for it. For ATI/AMD, those are the Catalyst 13.12.