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Journeyman III

how to use four 4870 X2 2GB graphics cards on one motherboard with SDK 1.3?

Does anyone have experience in using four 4870 X2 2GB graphics cards on the same motherboard with the Stream SDK?

That is, to be able to use all 6,400 stream cores for one application?

Did you use the MSI K9A2 Platinum motherboard?

Do the four 4870 X2 cards have to be of the same brand, or could they be different?

Did you have to connect all of them to monitors? Or, did you somehow trick them to think that they are connected? How?

How big of a power supply did you use?

Thank you very much!


11 Replies
Journeyman III

Hi Mike,

Not full four 4870X2, but only two 4870X2. Even with the half cores the room gets quite hot.... 😄

My MOBO is the K9A2 platinum with latest BIOS, Phenom 9950 (and soon Phenom II). I use a cheap 1KW PSU, which I would say would support two additional 4870X2 in the future. Four 4870X2 would require a good quality 1KW or above PSU (I recommend Corsair HX1000, which internally is exactly a Thoughpower 1500).

For booting GPUs in the 4870X2, you can use a dummy VGA load or DVI-I KVM, depending on your soldering ability or budget. although KVMs is nothing considering the cost of the 4 cards.

You could get better deals buying same brand cards at same time, but as long as they have same specs I don't see any problem as no crossfire is there, you treat them as 8 independent GPUs.

For dispatching work to different GPUs, you need some effort on your application, as is not automated.




Journeyman III

I believe these motherboards with their northbridge chipsets do not support full PCI-E Gen2 x16 on the four slots simultaneously. You can get a max of 2 slots x16, while the others will give x8 speed (half throughput). They are all "electrically" compatible with x16 card, but speed will differ. I suggest you look again into the datasheets for the chipset or motherboard

bayoumi is correct. The MSI K9A2 Platinum boards allows you to use 2 PCIe 2.0 x16 slots at x16 at a time. The two darker ones are x16 (slots 1 and 3 from top to bottom).

Scroll down to "Slots".
Journeyman III

thanks ryta123. This link states that with using 4 cards, the number of usable PCI-E lanes will be automatically switched to 8x/8x/8x/8x.

Confirmed. The light ones run at x8 maximum. If connect the 4870X2 card there the system won't even boot, at least mine. They require to be plugged into the full PCI-E Gen2 x16, so this limits a maximum of two 4870X2 cards with this MOBO.

Looking aroung for a full 4 4870X2 card capable mobo, i am also getting in troubles to find a good one.

= Asrock X58 supercomputer suffer the same limitation:  4 x PCI Express 2.0 x16 slots (blue @ x8 / x16 mode, orange @ x8 / N/A mode)

= Gigabyte GA-8N-SLI Quad Royal  suffer the same limitation: 4 x PCI Express 2.0 x16 slots (light blue @ x8 / x16 mode, black @ x8 / N/A mode)

As far as I know, the only MOBOs that would support four full bandwidth 4870X2 cards are unfortunately Intel LGA775 based:

- ASUS P5E64 WS Professional Workstation (my next purchase?)

- Intel Skulltrail D5400XS (3 max as 1 of the four is single spaced)

which is very dissappointing for the AMD fan I am...

AMD anyone?




ASUS P5E64 WS Professional is a problem too: two PCIex16 at x16 full-speed and two at x4 speed


Have you tried with 2 cards: one 4870 X2 in an electrical x16 slot + one 4870 X2 in an electrical x8 slot ? If it still doesn't work - wow big disappointment indeed. Another mobo that should support 3 dual-slot cards is the ASUS P6T6 WS Revolution (Intel too!).

This thread seems to suggest a 4870x2 can run in a PCIex8 slot

I have tried both the MSI GD70-790fx and the ASRock x58 deluxe, and neither allowed more than 2x 4870x2, while these motherboards are often used for quad gtx295 setups. 

The ASUS p6t7 has four simultaneous x16 slots, but its too expensive for an attempt ... to me this seems like a driver issue which the p6t7 might not fix.

Instead, I am going to try and run 2x 4870x2 and 2x gtx295 ... in my ASRock x58 (connectors are more clear around the PCI slots).  I guess I will succeed with that before I do with 4x 4870x2 ... unless some new drivers are released ... unlikely since 9.5 came out a few weeks ago.







Answering zpdixon: Yes, same result.

ASUS P6T6 WS Revolution seems the best choice up to 3 HD4870x2.

ASUS P6T7 WS Supercomputer seems the best choice up to 4 HD4870x2



Answering zpdixon & igimenez:  1 4850x2 in PCIex16 and 1 4850x2 in PCIex8 works fine for me on an ASRock x58 deluxe under Ubuntu 8.10 64bit, catalyst 9.5 (8.612) and Stream SDK 1.4:

emuller@XYZ:~/project/caltest$ ./caltest
CAL Runtime version 1.4.283
Found 4 devices. Using device 0.
Device Type = GPU RV770
Max 1D Width 4294967295.
Max 2D Width 8192.
Max 2D Height 8192.
Found 1024 MB GPU RAM.
Found 0 MHz GPU device clock.
Found 0 MHz GPU memory clock.
Found 10 SIMDs.
Wavefront Size 64 .
Device open and ready.
Found 1003 MB available GPU RAM.
Found 1966 MB available uncached remote RAM.
Found 59 MB available cached remote RAM.
Kernel compile and link sucessful.
Device sucessfully closed.

Adding another GPU, even to a x16 slot indeed running in x16 mode fails, in terms of a hardlock upon starting X.  Note that aticonfig --lsa can detect four 48X0x2 cards (the coveted 8 GPU setup) if X is not loaded at boot.  Similar result for a 790fx based MSI GD70, and for 4870x2s.  

My conclusion is this is NOT a x8 slot issue, and I will not be shelling out cash on a P6T7 to find it also not to work.   

Could anyone at AMD please confirm this is to be a driver issue, i.e. no support for >4 GPUs by fglrx ?




Hi emuller,

Thanks for sharing that info. I am not tested so extensively as you, but I was unable to boot a dual Sapphire 4870x2 setup in MSI K9A2 Platinum, as long as any of the 4870x2 cards was in x8 PCIe slot.

Only when both of them were installed in x16 PCIe worked for me. From you experience, it looks that in some MOBOs this could be potentially possible (I don't discard a BIOS/MOBO issue in my particular case, as K9A2 is rather old) as long as the drivers allowed that.

I agree 100% with you that It would be good to get a clear answer from AMD about that.