Without the Apple proprietary MPX slots, such cards will be limited to 75W bus power. PCIe bus on M2 Ultra is also limited to something like PCIe 4.0 16+8 lanes

Without the Apple proprietary MPX slots, such cards will be limited to 75W bus power. PCIe bus on M2 Ultra is also limited to something like PCIe 4.0 16+8 lanes, or 47.28Gbps(5.91GB/s) total. This will be much slower than competing(in price) product such as Intel Xeon W/AMD EPYC, which has up to 112/128 lanes of PCIe 5.0 or 441.28/504.32Gbps(55.16/63.04GB/s) max bandwidth. This means a M2 Ultra PCIe card/backplane desktop supercomputer takes 192GB/5.9GB/s = 32.54s per node minimum to fill the whole 192GB of RAM - I don't know how to interpret this, is this going to mean the cluster will be I/O limited, or will it be actually limited by CPU?