Crossfiring 3870x2

[samsonite789]

Quick noob question: can you crossfire two 3870x2 cards that are of different brands? Like, an ASUS and a VisionTek? If so, I read that it will use the lower end of the GPUs. Given that these are the same GPUs, what if one of them is GDDR4 memory, and has different clock speeds? Will it downgrade to the GDDR3 memory of the other one, or to the lower clock speeds? Thanks!

[glock19owner]

:welcome:

Yes on both questions...

I am running a 3870X2 (ddr3) and a HD 3870 (DDR4)...its does downgrade the memory on the Toxic...but not much...but if given...you should really run the same memory...DDR3/DDR4...

You can compensate on the GPU clock speed by overclocking the lower GPU X2 with AMD GPU Tool...

[samsonite789]

Thanks, man! Another question: what exactly is the performance difference between DDR3 and DDR4? I guess it's moot since you say that the DDR4 will downgrade to DDR3 if crossfired with a DDR3 card. Also, what would the actual performance difference of two 3870x2's crossfired be as opposed to a single 3870x2, and how much power would it take to run such a beast?

[DaPoets]

:welcome:

Yes on both questions...

I am running a 3870X2 (ddr3) and a HD 3870 (DDR4)...its does downgrade the memory on the Toxic...but not much...but if given...you should really run the same memory...DDR3/DDR4...

You can compensate on the GPU clock speed by overclocking the lower GPU X2 with AMD GPU Tool...

How much of a performance increase did you see adding the 2nd card (3rd gpu) in your 3Dmark06?

[glock19owner]

XP none...it wont support Tri-Fire...Vista...almost a 3K plus just adding the other 3870...

[DaPoets]

XP won't support tri-fire huh? so that's why my Quad-Fire didn't improve my benchmark?

[glock19owner]

Yeap...best way to tell if tri-fire is working...run 3d mark 06 pixel shader test only...you should be in the upper 1140+ FPS...if you are in the 700's...your running the X2 alone...

[killuazaoldyeck]

XP won't support tri-fire huh? so that's why my Quad-Fire didn't improve my benchmark?


we have the same problem. in my case, my single card score is 15000's, crossfire 14700's, no oc cpu & gpu. so let me try installing vista.

[DaPoets]

Installing vista64 did the trick for me. All 4 GPU's are active.
God I hate vista.

[glock19owner]

If that is true...then when you run 06 pixel shader test...you should be in the 1400 range...if you are getting in the 700 range...its still just in CF...I just installed my other X2 and XP sees all of the GPU's and swears quad is enabled...and GPU swears all 4 GPU's are enabled...but the 06 test is the dead give away that I am still only running CF not quad

Please post back what framerates you are getting in that test...I have been debating on going with XP 64...and if you truely have quad fire enabled...that seals the deal for me...

[Brolloks]

I have been debating on going with XP 64...and if you truly have quad fire enabled...that seals the deal for me...

LMK too if that works 'cause I just hate Vista and also cannot get quad fire to work in XP, even with the latest drivers:bang head:mad:

[DaPoets]

Again, XP can not use more than 2 GPU's no matter what the drivers are. Even in CCC it will only show you 2 GPUs in the crossfireX section in XP. When you use vista (dual boot to try it out) it will show you 2,3,and 4 gpu's that you can use for crossfireX. I played around w/ the 3gpu crossfireX for a bit because I wanted more than 2 monitors running which is possible if you have 4gpu's. But when you enable cossfireX for all 4 GPU's then you are limited to 2 monitors.

XP = 1,2 GPU's
Vista = 1,2,3,4 GPU's

[DaPoets]

I have not ran the framerate test but my 3DMark03 score w/ QuadFire enabled puts me in the top 10 on OCForums... I say it works just nicely. 3DMark06 doesn't do all that well w/ more than 2 GPU's just like Crysis.