This board was used primarily in Altair 8800bt Turnkey systems which did not have a full front panel, however, the board could also be used in a full front panel 8800 and provided a few useful features:
- 1K of PROM space in four 1702A sockets (already present in the Clone)
- 2SIO-like port at I/O address 0x10 (already present in the Clone)
- Auto-start at a specified address on power up or following a front panel reset
- The on board 1K of PROM at 0xFC00 to 0xFFFF can overlay system RAM at the same address. PROM is enabled at power up and on reset. The PROM is disabled and RAM enabled upon execution of an IN instruction from I/O address 0xFE or 0xFF. This allows system access to a full 64K of RAM even after using boot PROMS to boot.
Without the Turnkey board installed, resetting the computer from the front panel does a warm start, executing from address zero, for BASIC, Altair DOS, and for CP/M. However, with the Turnkey board installed, reset performs the auto-start function instead of running from address zero. If the disk boot loader is specified as the auto-start address, a front panel reset performs a cold start boot of of the floppy instead of a warm start.
NOTE: Installation of the version 1.8 update from a previous version re-initializes all saved parameters and erases all disk content and PROMs. Save any custom floppy content on the floppy drives to a PC if needed. PROMs and floppy content will have to be reloaded after this update is installed.
Feel free to contact me with any questions!
Mike