Sorry for the late reply but, lots of work and computer is getting me crazy
I think i have tested all possible setting...dam hard.
What is your power supply for 4x590?
I'm using 2 PSUs, linked with Add2PSU adapter. 1000w + 900w
I managed to get 4 GTX590 working, but only if connected directly to the MB pci slots....but temps just go UP because there is no space to get enough air in. Tested to see if was a power problem but...it works very well, 1600w power draw...so 1900w is more then enough.
When using risers...cant get them to stay stable...lots of freezes, crashes, blue screens...
with 16x to 16x - NON powered - blue screen
with 16x to 16x - powered - random freezes - Drivers Crash...etc
with 1x to 16x - powered - random freezes - Drivers Crash...etc - only works in 1x pci MB slots
with 1x to 16x USB - powered - random freezes - Drivers Crash...etc - only works in 16x pci MB slots
(don't know why) it should work in 1x too.
But the 1x to 16x USB Powered are the more stable I get, as I only have 1 of these I ordered 3 more so I can connect the 4gtx590 with the same kind of risers. The only thing I think may be causing the crash/freeze was the use of different tipe of cables (1x to 16x, and 1x to 16x USB, don't work the same way and might be causing the problems)
I´m waiting for new cables so make some final tests.
Im the process I bought a Nvidia FX Quadro 1800 to display (used one - 50€), is not as good as the gtx590 to model and 3d aplications but I think its good enough so I can free the 590's to render.
At some point I managed to get 4gtx590+FX1800 working (FX1800 to display, 2gtx590 inside the case and 2gtx590 outside with risers)
I thought it was all good......but.......
Evga Precision, and MSI Afterburner can't control 9 GPUs.....??
While trying to get a solution to that problem I lost so much time I was forced to get back to 1 FX1800 + 2gtx590 so I can get my projects going...I'm already to late and now need to step up and get my works up to date.
When the new USB risers arrive I will test again.
The problem with the 9 gpus really troubles me because in Evga Precision and MSI Afterburner the Gpu Fan´s of the gtx590 is controlled in pair, because 1gtx590 have 2 gpus(1 is master and 1 is slave) the apliucation read the temps from the master Gpu and then increases the fan speed. The 9 gpu problem comes because, only 8 gpus are displayed in Evga Precision and MSI Afterburner, so one of the Gpu's of the last gtx590 is not read, this last Gpu is the master of the 4th gtx590....so it get hot as the fan stays slow.
When this was just to let you guys know how its going.
I will come up with a solution...but for now....lots of work need to be done. Shame I still can get to use full rendering power...for the 5 or 10 minuts I managed to get the to work....rendering was sweeeeeeeeeeeet