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The specs for 2019 Mac Pro states 4 Double wide slots, and 8 slots in total. How many graphics cards can I stuff it with? . Since most GPU's are double wide cards, can 4 AMD VEGA II Duos be added to the 2019 mac pro?
Agreed, eGPUs are probably a bad idea if you have a computer with real PCIe slots. Not only are those limited to PCIe x4 per thunderbolt bus but the thunderbolt protocol also adds a little extra latency. Rob with Barefeats.com demonstrated that direct PCIe host-card-to-expansion-box solutions work much better. https://barefeats.com/mac-pro-2019-na255a-pcie-expansion.html
Anyway, the 2019 Mac Pro has the following limits:
Each MPX modules uses 2x 8-pin AUX connectors limiting you to 4x GPUs if using Vega II Duo modules.
If you bring your own cards you are limited to 4x 225W 1x-8-pin double-width cards, or maybe 8x 150W 1x6-pin single-width half-length cards. (Disclaimer: Apple only advertises 4x GPU support so there might be a limit to how many MacOS can recognize).
For full official technical specs see the white paper. https://www.apple.com/mac-pro/pdf/Mac_Pro_White_Paper_Feb_2020.pdf
For even more cards (or cards with more power) PCIe expansion enclosures are the only way to go. Theoretically If you populated every full-length PCIe slot with an adapter card you could run 29x PCIe devices each at either 3.0x2 or 3.0x4 speeds, but again MacOS limits might kick in earlier.
Agreed, eGPUs are probably a bad idea if you have a computer with real PCIe slots. Not only are those limited to PCIe x4 per thunderbolt bus but the thunderbolt protocol also adds a little extra latency. Rob with Barefeats.com demonstrated that direct PCIe host-card-to-expansion-box solutions work much better. https://barefeats.com/mac-pro-2019-na255a-pcie-expansion.html
Anyway, the 2019 Mac Pro has the following limits:
Each MPX modules uses 2x 8-pin AUX connectors limiting you to 4x GPUs if using Vega II Duo modules.
If you bring your own cards you are limited to 4x 225W 1x-8-pin double-width cards, or maybe 8x 150W 1x6-pin single-width half-length cards. (Disclaimer: Apple only advertises 4x GPU support so there might be a limit to how many MacOS can recognize).
For full official technical specs see the white paper. https://www.apple.com/mac-pro/pdf/Mac_Pro_White_Paper_Feb_2020.pdf
For even more cards (or cards with more power) PCIe expansion enclosures are the only way to go. Theoretically If you populated every full-length PCIe slot with an adapter card you could run 29x PCIe devices each at either 3.0x2 or 3.0x4 speeds, but again MacOS limits might kick in earlier.
Per the specs: "Taking power one huge step further, Mac Pro supports configuration of
two Radeon Pro Vega II Duo MPX Modules. The four GPUs combine to add up
to 56 teraflops and 128GB of high-bandwidth memory". For added video processing you can also add an Afterburner, a hardware accelerator card built with an FPGA, or programmable ASIC.
I am trying to get to 8 GPU's (for custom software development ). The Afterburners would be great if Apple would provide info on how to re-configure it (they don't). I need to re-create this https://www.orangesv.com/blog/what-it-took-to-build-one-of-the-worlds-fastest-off-the-shelf-single-node-gpu-supercomputers/#.Xs74ytJQ-7c.linkedin but with AMD GPU's.
The Problem with eGPU's (for my particular application) is that it's like drinking Molasses through a Martini straw. Thunderbolt 3 constrains PCI-e GPU cards to 4 lanes of PCI-e bandwidth vs 16 lanes when it's plugged directly into the motherboard. When you have multiple cards you have to shuttle data back and forth to the CPU. The MacPro/ AMD Vega Duo's use an Infinity Fabric to move data directly between pairs of cards (because it's much faster than PCI-e ), but that is for only pairs of Vega Duo's .
Each Vega II Duo MPX modules takes up the two slots of an MPX bay, of which there are two at the bottom of the chassis. that gives you four GPUs linked together in pairs.
There are four additional PCI-e slots. Three are single-wide, and the top one is Half-length and is filled with the the I/O card in it standard.
So I only see space for one more "regular double-wide" PCI-e GPU card, and no way to tie it to the others with a private Bus. Unless you toss out the I/O card, then you have space for at most two "regular double-wide" GPU cards, not tied together. whether there is enough power for all that stuff is questionable.
I think you should look at other solutions -- it appears this chassis really wants to be a Mac, not a specialized Server.
That's pretty insane! Looks expensive, too. Have you considered an external GPU (eGPU)? Take a look at this write-up https://support.apple.com/en-us/HT208544
Thanks all for the info. 8192x2 (2 Vega II Duo's) = 16,384 Stream processors . Wiith Apple's Metal API should be enough to simulate 1 Billion particles.
2019 Mac Pro how many graphics cards can I add
