Re:Nvidia GeForce GTX 1080 Ti
by ansible on Wednesday March 01, 2017 @04:33AM
(#13762500)
Some of the high end Xeon systems have gobs of PCIe lanes. If you have a four CPU socket system, you can hang four x16 PCIe cards off of each processor.
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4CPU sockets !=> 4x x16 cars. It always depends on the number of PCI lanes for each processors. Check i.e. these 2 E7 Xeons: http://www.intel.com/content/www/us/en/products/compare-prod...
Both have max 32 PCI Express lanes - so you can theoretically hang max 2 PCIx x16 cards off each CPU, but as few of the lanes is reserved for other peripherals, in 4GPU/CPU setup they will practically run at lower speeds, ie 8/8/4/4. However, using system with PCIe root complex [1] can improve the GPU<->GPU communication speed.
[1] https://www.microway.com/hpc-tech-tips/pci-express-root-comp...
Or get specialized board with PCIe switch ie. http://www.cirrascale.com/blog/index.php/welcome-big-sur/
so GPUs get better bandwidth (P2P etc).