PCIE problem - number of cards = slow throughput

tribz

tribz

tribz

Soldato
Joined
4 Mar 2008
Posts
2,648
Bit of a head scratcher for me this.

I've got an Asus P6TSE X58 board which gives the following 3 x PCIe 2.0 x16 (at x16/x16/x4 mode)

I've got a 5870 in the top slot and a 3Ware 9650SE RAID Controller in the bottom slot. The 9650SE is a x4 connector.

Its all been working great until I've added a second 5870 into the middle slot to crossfire it. As soon as I've done that, throughput on the 9650SE array has plummeted from 250Mb/s to around 50Mb/s. Everything crawls.

If I remove the second 5870 then all ok again. If I put the 9650SE in the middle slot and the 5870 in the bottom, the 9650SE works at full speed but the 5870 isnt recognised (unknown device). The slot works fine because the 9650SE works fine in it.

Am I right in thinking this should work at x16x16x4 on a X58 chipset ? I've updated the BIOS to the latest available.
 
Even at PCI-E v1 1x you should be getting 250MB/sec so I suspect this is something other than PCI-E speeds. Some other conflict?

What if you swap the 5870s?
 
I think that might be my next thing to try. Slightly hampered by them both being water cooled. I can move the bottom one easily enough but theres not enough tube on the top one to move them so I'll need to re-do the loop to test.

Had a google around and people are tri-firing on these boards so it must work ok.

So far I've reloaded Windows 8 from scratch to test and also tried it under 2012 server. Same problem on both
 
Can you run the full screen gpuz render test, it should at least tell you what's happening with the pcie lanes the gpus are on. See if anything looks out of the ordinary.
 
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