itsmydamnation
Veteran
Yes i would assume that GMI is PCI-E physicals/encoding. I've been looking at die shots trying to get an idea of the possible amount of of PCI-E in the zeppelin dieshot by roughly comparing the relative size of a PCI-E interface to the memory interface. the best comparison i have so far has been to use the good bulldozer die shots and use the HT links as a guess. Each HT 16bit (32bit bidir) link is 76pins. PCI-e 16x is around 160 pins. On Zambezi the HT links are spread thin on mangy-cours they are wider but shorter. it looks like you can get aprox 8 HT interfaces in the same space as the 128bit memory interface (608 HT pins).
On Zeppelin each gmi interface is about 2/3 of the width of the 64bit memory interface but it is about a 1/3 longer, the two GMI interfaces in total would be around the same size as 128bit DDR interface. So that is aprox 608pin which is aprox 64 lanes of PCI-E.
So now the question is how much interconnect between Zeppelin SOC's is enough ? is 16 lanes (25gbps) enough? if so two Zeppelin SOC's could provide 64 lanes to GPU and 32 lanes to motherboard based PCI-E. So long as shortest path is taken between CPU and GPU then the small inter zeppelin GMI link shouldn't be a problem.
On the 32core part a full mesh would leave a total of 64 lanes for PCI-E if its a dual ring then 128 lanes.
So hows that for a mighty long bow! .
On Zeppelin each gmi interface is about 2/3 of the width of the 64bit memory interface but it is about a 1/3 longer, the two GMI interfaces in total would be around the same size as 128bit DDR interface. So that is aprox 608pin which is aprox 64 lanes of PCI-E.
So now the question is how much interconnect between Zeppelin SOC's is enough ? is 16 lanes (25gbps) enough? if so two Zeppelin SOC's could provide 64 lanes to GPU and 32 lanes to motherboard based PCI-E. So long as shortest path is taken between CPU and GPU then the small inter zeppelin GMI link shouldn't be a problem.
On the 32core part a full mesh would leave a total of 64 lanes for PCI-E if its a dual ring then 128 lanes.
So hows that for a mighty long bow! .