What is the highest number of PCIe x16 slots current CPUs allow?

[NicoV]

I can't imagine that anyone would actually have a use for this-but how many PCIe x16 slots can you get in one system? I know that there are servers that have 8 Intel Xeon CPUs in one system. However Xeon has a lot fewer lanes than EPYC. And the EPYC platform has some dual socket motherboards.

[Electronics Wizardy]

Do you allow pcie switches? They allow for most pcie lanes than the cpu have alone. There are many servers with 10 x16 slots for gpu compute.

 

 

 

EPYC single and dual socket normally have the same number of lanes, as some of the lanes are used for cpu to cpu communication(simple explination)

[TheBean]

each cpu can support a different number of PCIe lanes. it is up to the motherboard how to split them up. Some motherboards give you more x4 slots, but reduce x2 slots, some will give you more x8 slots and reduce x16 slots etc. 

 

 

[Jurrunio]

Each Eypc CPU gives 128 PCIe lanes so you can extrapolate from that. Of course then comes the board space issue, sometimes the board just isn't long enough for so many PCIe slots with sufficient spacing between them (typcially 2 slot, since systems that need so many PCIe slots will run high power draw stuff that needs space for cooling)

[Chris Pratt]

42 minutes ago, NicoV said:

I can't imagine that anyone would actually have a use for this-but how many PCIe x16 slots can you get in one system? I know that there are servers that have 8 Intel Xeon CPUs in one system. However Xeon has a lot fewer lanes than EPYC. And the EPYC platform has some dual socket motherboards.

When you're talking about servers, I'd imagine there's a ton of people probably saturating the PCIe lanes. Remember that GPUs aren't just for gaming; they have uses in AI. Also, there's actual game streaming now, and I'd imagine the likes of Nvidia, Google, and Microsoft are fully loading out their servers for their streaming platforms.

[NicoV]

2 hours ago, Chris Pratt said:

When you're talking about servers, I'd imagine there's a ton of people probably saturating the PCIe lanes. Remember that GPUs aren't just for gaming; they have uses in AI. Also, there's actual game streaming now, and I'd imagine the likes of Nvidia, Google, and Microsoft are fully loading out their servers for their streaming platforms.

I was actually thinking about super high bandwidth PCIe storage devices for data crunching and AI accelerators (Sort of like a PCIe version of the DGX). Something like Liquid's compose-able infrastructure (I think that's what its called) that Linus showed in the "This is 50x faster than your PC" video. I said no one would have a use for it because of the massive side needed for a motherboard that can use the 6 or 7 possible x16 slots of a single EPYC CPU would make it impractical.