Crossfire question

[Doco]

Hello all, just a few questions for some people running a crossfire setup (or just general knowledge about it).

Anyways - I received my 2nd 7950 Iceq Boost yesterday (with free games...and haribo ) and decided to do some tinkering - removed my old 7950 ( overclocked as referenced on sig @ 1200/1425 on stock) and initially my card seemed like it may have been dud - crashing with general overclocking on the core, however things took a bit of a better turn when I hit the memory overclocking as it proved quite eager to impress me - as it stands Ive currently got my card at 1050/1575 on stock (see what I mean by the core clock not wanting to play ball :-/, ive not tried to push past the 1575 yet and I'll get to why in a sec) - Ive run heaven 4.0, 3d mark 11 and the more recent 3d mark so I know the memory clock may not be set in stone - about to do some real world gaming runs and see how it holds up (if it does then I may try above the 1575 mhz).

Now my question is this - when ever I get a new psu that can power a crossfire setup - lets just say that my new card wont budge above 1050/1575 - even if I decided to start increasing voltages to the core, -how will this effect a crossfire setup with two cards running at completely different speeds - with 1 ahead on the core and the second ahead on the memory, I'm pretty sure I read a while ago that the obviously work better if they are at the same clocks / are within a % to each other -

So am I safer down clocking both cards so they are running at the same settings or should I just leave them both clocked as it is - if you answer is "just run them overclocked at different settings" would it then matter which card I have as my primary and which is secondary (i.e better to have main card with a higher memory clock or a better core clock ....or does it not matter and I'm just thinking too much about it lol)


Apologies for the long read and thanks in advance on any input

 

[oldestgregg]

The way it works now is AMD allow both cards to run at seperate speeds but I sync mine through afterburner anyways. As long as both cards are being utillised ,I wouldnt imagine it will matter which is the primary card but I would have the fastest as card number 1 just in case only one card is working in game. Hope that helps some

 

[Final8y]

The way it works now is AMD allow both cards to run at seperate speeds but I sync mine through afterburner anyways. As long as both cards are being utillised ,I wouldnt imagine it will matter which is the primary card but I would have the fastest as card number 1 just in case only one card is working in game. Hope that helps some

It has always worked like that.

 

[Doco]

So ive just seen - What happens when graphics cards with varying memory speeds and engine clocks are paired together?

The overall performance will be adjusted to match the memory speeds and engine clocks of the lower clocked card. To obtain the ideal performance, graphics cards should be paired correctly using the AMD Crossfire compatibility chart.

On the amd website - so crossfire adjusts itself to use only the lower clocks then - stupid silicon lottery eh lol

Thanks for the info sofar