Linux is well SMP'ed by now. I'll let Linux show off a 'top' listing :
top - 21:49:27 up 2 days, 8:16, 2 users, load average: 0.19, 0.20, 0.18 Tasks: 123 total, 2 running, 121 sleeping, 0 stopped, 0 zombie Cpu0 : 0.7% us, 1.7% sy, 0.0% ni, 97.4% id, 0.0% wa, 0.0% hi, 0.3% si Cpu1 : 0.7% us, 1.3% sy, 0.0% ni, 97.7% id, 0.0% wa, 0.0% hi, 0.3% si Cpu2 : 1.0% us, 2.7% sy, 0.0% ni, 93.4% id, 0.0% wa, 0.7% hi, 2.3% si Cpu3 : 2.7% us, 5.0% sy, 0.0% ni, 92.0% id, 0.0% wa, 0.0% hi, 0.3% si Mem: 1033572k total, 360752k used, 672820k free, 48612k buffers Swap: 524280k total, 0k used, 524280k free, 153668k cached
That is 4 cpu's in action. This particular Linux works find even with 64, but the hardware better have something like NUMA to keep up feeding data to all those CPUs.
The list of the OS'es that made it to the 64 CPU mark is still pretty short. I am not aware FreeBSD made it past 32, and that leaves Solaris, Irix, AIX and Linux.
I think you *can* use gdb to debug the kernel if you have it running inside another kernel. One neat trick in...
The debugger companion to the gnu toolchain is gdb. It has a number of incarnations, but they appear...
On *n*x it is called screen. Works like a combination of ptycon, attach and detach; plus it can watch the screen for you while you are gone.