I remember CP/M with fondness. My father gave me an Osborne 1 for my first computer when I was 12 (41 years ago). It came with CBASIC2 as well as MBasic, and I managed to find a Lisp (I forget what flavor). To put the Osborne 1 in perspective, the stats:
The multiply instructions on later CPUs were implemented as microcode programs on the silicon, so sometimes it was faster to write your own or a specialised routine anyway.
* 64kb memory (yes that's kilobytes)
* 2 5 1/4 floppy disks
* No hard disk
* 5" monochrome green screen monitor
* 4 MHz CPU
* 37 watt power supply
* weighed ~25 pounds