Comment by ryan_glass

Basically it comes down to memory bandwidth of server CPUs being decent. A bit of oversimplification here but... The model and context have to be pulled through RAM (or VRAM) every time a new token is generated. CPUs that are designed for servers with lots of cores have decent bandwidth - up to 480GB/s with the EPYC 9 series and they can use 16 channels simultaneously to process memory. So, in theory they can pull 480GB through the system every second. GPUs are faster but you also have to fit the entire model and context into RAM (or VRAM) so for larger models they are extremely expensive because a decent consumer GPU only has 24GB of VRAM and costs silly money, if you need 20 of them. Whereas you get a lot of RDIMM RAM for a couple thousand bucks so you can run bigger models and 480GB/s gives output faster than most people can read.