A PC machine in the company has three 16x pci-e slots, let's call them A B C (A is closest to the CPU, C is furthest). There has been two graphic cards installed in it (gtx680 in A and gtx560 in C, all used for some kind of gpu computing) and all work well.
Then the new pci-e card is developed by ourselves and is used to acquire some data from the outside world.
Then the problem comes, if all three slots are used (install the new card in B), the PC will fail to start up in most cases (The new card can't be recognized by OS when the PC can start up occasionally).
Then we did some experiments:
If we remove the graphic card in A, the PC will start up without any problem, the new card works well either in A or B.
If we remove the new card and install the gtx680 in B, the PC will start up also (by observing the keyboard status and HD activities indicator), no display though, some configuration may be needed.
If we install the new card in A and gtx680 in B, the PC also failed to start up.
So, what's the possible cause for the problem? Do I need to do more research? about what?
I hope I've made myself understood and any suggestion would be appreciated.
The PSU we're using is labeled 1000W, also, when we're using the two gpu configuration, the pc can work well for a whole day without any problem when the 680 is full utilized by some cuda application.
The card we developed can work in other normal pc (lenovo or dell) which has onboard graphic card only. The problem machine isn't from those well-known brand like dell, lenovo, etc. Its mainboard is labled with EVGA.