Sapphire 7950 2 of 4 have low hashrate

[mrbrdo]

Hey guys, I have a weird issue with my 7950s.

They worked fine at 620 KH/s, but they hanged twice during last 2 days (it seems like machine kept mining actually, but I could not ssh into it anymore or access the web interface).

After today's hang 2 cards did not work (cgminer showed 511 C temp, 0 fan, no hashrate but no dead/sick either). I tried rebooting a few times but same story (cgminer works, but 2 cards showing that weird details).
I disconnected 2 cards but cgminer wouldn't start then, it seems the driver did not detect any cards or there was some error. After that I disconnected one more, that worked, then I connected back 1, it worked now (wtf?), then I connected all 4 cards and they all work now.

I was mining Vertcoin (using vertminer) while this happened, but I don't think it could have anything to do with it. I was on BAMT 1.3.

However now 2 cards have a hashrate of 775 KH/s, while the other two have same as before (620 KH/s).

Card: Sapphire 7950 with Boost
Mem clock: 1250
Engine clock: 1010
Undervolted @ 1.081 V

[how-high]

I have 2 7950 cards, actually3 but only 2 in this rig while waiting for an extra riser
anyway 1 got 630kh/s
while the other start also at 630kh/s
but then quickly goes down to 550KH/s or something

to 1 I have a monitor connected, to the other nothing
maybe because there is no monitor attached speed goes down?

I am waiting for some dummy plugs to arrive to test it

any way to see which gpu0 and gpu1 is which card?

[mrbrdo]

Not easily, but you can put fan speed to 100% for one card and see which one it is.

It is not related to plugs, I never needed plugs on these cards before.

[how-high]

yes I can now confirm
with dummy plug still 1 card lower then other
so what else could be our problem?

ps I changed the cards and its still gpu1 that's slower

[mrbrdo]

I don't think it's the same issue that we have.. How much lower is your hash on the other card?

I have to say Sapphire 7950 seem to be the worst cards that money can buy :-/ Just so unreliable!

[how-high]

good one is 630 kh/s
and bad one goes quickly down to around 550 kh/s
will try some more things and otherwise I think I will open my own topic
anyway if I will find the solution I let you know

[mrbrdo]

Thanks.