> Some multi-core processors come with less L2 cache than their multi-CPU > counterparts.
This, and your other arguments, while valid, apply independently of the CPU. There are a lot of factors that determine compile speed. FYI SGIs tend to have crossbars. > Was that UMA or NUMA, and how far up could you scale N usefully? UMA I think. We generally had just 1 and 2 CPU machines. > Do you know if software RAID (not so much R as A of ID) is effective > at avoiding I/O bottlenecks, e.g. will two disks for four cores work > as well as one disk for two? Disk is so much slower that CPU that I don't think it matters. Software RAID is already faster than hardware RAID for common uniprocessor systems, assuming you don't introduce I/O bottlenecks (like 33MHz PCI bus). For example, my server here is a dual opteron, with an 8-sata controller. It works because the PCI bus is a 133MHz 64 bit bus, which I calculated was sufficient to host all eight drives. I was able to benchmark a 7-disk RAID array at 250MB/s sustained.
