The disk images here are standard Altair CP/M 2.2 disk images, however, the
CP/M 2.2 on the boot tracks is customized for a Sol-20 computer. 

IOBYTE values 0-3 select Sol-20 pseudo-ports 0-3. Port 3 (user port) drives
the first port on an Altair 88-2SIO serial board (I/O address 10h/11h). The
default IOBYTE is:

  CON: is TTY: Sol-20 keyboard and video display
  RDR: is PTR: Sol-20 serial port
  PUN: is PTP: Sol-20 serial port
  LST: is LPT: Sol-20 parallel port

On the system disk, PCGET/PCPUT uses the Sol-20 serial port for transfer.
PCGETA/PCPUTA uses an Altair 88-2SIO serial port for transfer.

These disk images can be written on an Altair computer using PC2FLOP. I might
get around to writing a Sol-20 version someday. The disk images can also be
used with the serial disk server feature of the Altair FDC+.