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7950 Crossfire advice and info

xTommy92

xTommy92

xTommy92

Associate
Joined
21 Jan 2013
Posts
439
Hi guys,

Since OCuk have had a massive AMD sale I am considering getting another Twin Frozr 3 7950 for myself. The reason I started this thread was for some information and advice on crossfiring, are they any serious issues I should know of before diving in?
Also I will need to change Mobo, is that a lot of hassle as I currently have a Z77-D3H Gigabyte?

Any help or advice would be highly appreciated, Thankyou,
Tom
 
Your board supports Crossfire, but it's not ideal (x16x4). I'm not sure it's worth changing the board for, especially for an old platform.

Your PSU can handle it, though check that you've got the right cables in case you need any adapters (you should get some with the card anyway).
 
I've tested this using a x16 x4 board vs a x8 x8 board. The difference is generally around 5%. Though in certain circumstances it can be more or less. Worst case about 10% but mostly around 5% or less. I would still advise you to get crossfire, even with a x16 x4 setup. But you should be looking to go x8 x8 minimum as soon as possible to get the full benefit.
 
xTommy92 said:
Cool thank you Matt, is there any issues with crossfiring that I should know of?

Tom
Click to expand...

Nothing major, any small teething problems we can help you overcome most likely. Just ensure you have a suitable psu, case cooling and a fast enogh cpu to drive the cards.
 
Hi - I asked this in the AMD offer thread but think it is related here (my mobo is also 16x/4x in xfire) :

Damn car tax means a 2nd 7950 this month is probably out the question for me. I wonder though, in crossfire, is the performance hit on the second card down to the PCIE bus ? If you put a faster performing 7970 in the second slot, would it cancel out the reduction and equal 7950 crossfire (I know of would down clock to the 7950 speeds but whether the Extra stream processors etc would help) ? Just a thought . . .

Any thoughts ?

CJ
 
cjph said:
Hi - I asked this in the AMD offer thread but think it is related here (my mobo is also 16x/4x in xfire) :

Damn car tax means a 2nd 7950 this month is probably out the question for me. I wonder though, in crossfire, is the performance hit on the second card down to the PCIE bus ? If you put a faster performing 7970 in the second slot, would it cancel out the reduction and equal 7950 crossfire (I know of would down clock to the 7950 speeds but whether the Extra stream processors etc would help) ? Just a thought . . .

Any thoughts ?

CJ
Click to expand...

Look a few posts above you. :p

LtMatt said:
I've tested this using a x16 x4 board vs a x8 x8 board. The difference is generally around 5%. Though in certain circumstances it can be more or less. Worst case about 10% but mostly around 5% or less. I would still advise you to get crossfire, even with a x16 x4 setup. But you should be looking to go x8 x8 minimum as soon as possible to get the full benefit.
Click to expand...
 
Forgot to mention the reason in wanting to crossfire is that a am using a 144hz Monitor at 1080p but more frames in a lot more of my games, especially since next-gen is near!

Tom
 
Right I am getting some very high temps at the moment while trying to OC my card a little more. I am following Matt's tutorial of overclocking at I am currently at 1155/1250 (still need to do Memory) @1200v and my card's average temperature is 80 Degrees and max is 96 Degrees, this is scaring me a little, what would be the best thing to do to lower these temps, I was thinking of maybe re-applying TIM?

Tom
 
Forgot to mention that I have an attic room which normally tends to affect my temps depending on the year, in winter it is like LN cooling for my PC due to lack of central heating in the house.

Tom
 
That does seem a bit hot. You've got the fan on auto, and a good case ventilation?

Are you stable at 1150MHz at any voltage lower than that?
 
1150 was what I got upto last night, I will have more of a play around later but doesn't seem that I will get any lower on the voltage, once I get the other card I will more likely back down to 1100. It was just the temps that worried me and even at 1100 I am still going in to the 80's and once the second card goes in the temps are going to be horrid.

That is why I wondered about re-applying TIM.

Tom
 
Yep while benchmarking and overclocking I set the fan speed to a constant 100%. I also have 6 fans in the case, 1 front and 2 side that are intake and 1 rear and 2 top that are exhausts.

Tom
 
xTommy92 said:
Yep while benchmarking and overclocking I set the fan speed to a constant 100%. I also have 6 fans in the case, 1 front and 2 side that are intake and 1 rear and 2 top that are exhausts.

Tom
Click to expand...

Make your two side fans exhaust and make your top two fans intake, that will bring gpu temps down. What are you using to bench, Unigine Valley or something else?

Your temps do see a big high for Valley benching. You really want to be below 80c. Unless you can lower voltage to keep temps down id probably leave it there for now.
 
Yep Matt I am using Valley, very good bench to be honest. I will have a go switching the fans round and see what the temps are like. Should I still keep the front an intake?
I only followed your OC guide for about an hour, so will have to have a play around abit more but once I hit around the 1050 mark I had to keep bumping the voltage up at every clock increase as it kept crashing.

Tom
 
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