Expandable machines are attractive when the future is uncertain. I imagine a server chip would have abundant DDR6 and PCIe lanes. Oddly enough I’m now buying my PCs with all memory slots occupied because of bandwidth. I can still change the sticks for higher capacity, but expansion is a lot less convenient than when memory bandwidth wasn’t something more desirable than raw CPU performance.

I’m not sure if I can measure IPC and cache misse latencies on my machines, but I’m sure latencies are pushing IPC down.