Multi GPU matched pairs more efficient or no?

so heres an odd one that I have been pondering a while.
in the realm of multi GPU systems do matched pairs (same make brand even specs everything exactly the same) show any sort of gain or efficiency to unmatched pairs (2 different makers or revisions or chip suppliers ect)

the reason I ask is because I am not only running a unmatched pair from brands but also generations. one card is a 7870, the other card is a R9 270X, one is MSI and the other is Gigabyte.
they both run at the same speeds, I make them do it but they do it (both OCed mildly) and yes, it works.


I couldn't really find a whole lot of info, just speculation. I did about 9 months ago get a TON of old bit coin mining rigs from a relative and one of them had a pair of powercolor R9 270s (and a 1000W corsair PSU oooOOOoo)
so I could try and see, make everything run the same speed. i'll have to set up a test bench because I don't want to use my main computer for it. I think there was a first generation i7 out there in all that stuff maybe i'll see if I can use it or whip something up with my own old spare parts.

what do you guys think?

IIRC the HD-7870 and the R9 270x are base roughly off the same chip. This is one of the BIG sellers that AMD has not push like they should, being able to take TWO (2) cards from different generations (same chip) and still be able to CF them. Using the older card with the new one might cost you to have to run the newer one at a lower speed. There is no degrading of performance from using TWO card of the same chip from different manufactures, different revisions, or chip suppliers. IIRC you can't go this with NVidia cards. The same is true with the HD-7950 and the R9 280/285 and the HD-7970 and the R9 280X.

They are the same chip, you dont even need them at the same speed, i just always did to try and avoid anything that could help cause uneven framerates. And you can crossfire any same family gpu.

7850/7870/270/270x

7870xt/7950/7970/280/280x

etc

Like ST said, 270x and 7870 are the same exact card. Not similar. Same card (different clocks).

7870 = 270x
7850 = 270
7970 = 280x
7950 = 280

mmm no. same specs different power usages due to boost clock on one but not boost clock on the other but the point still remains.
theres a revision here between the 7870 and the 270x I have and an approximate 1 1/2 year difference between the 2 aswell.

they are the same card, they have different tdp limits and clock speeds (due to different bioses), but they are functionally the same card. Running at the same speed they will have identical performance, and people have even bios flashed 200 series bioses onto 7000 series cards. Much like how the 7950 and 7950 boost were the same card with different bioses and tdp limits, and 7970 and 7970ghz where you could cross bios flash.

I used to run a 7950 and a 7950 boost in crossfire, they were both running a custom non boost bios, because they were identical cards with different bioses for marketing reasons. The same reason almost the entire 200 series and 300 series exists, marketing.

my 280x shows up as a 7970 one time in a fresh windows install, next time it might show up as a 280x on a fresh windows install.
both my 280x do this same thing, one is a sapphire, one is an asus.
7970=280x, even gpu-z cant tell which is which, apparently.

Ahh the old days. When multi-gpu configs only had small gains.

Everyone should look at the Fiji cores and their crossfire scaling.

http://www.eteknix.com/amd-r9-fury-x-4gb-graphics-card-crossfire-review/3/
http://ocaholic.ch/modules/smartsection/item.php?itemid=1638&page=1