Altair Turnkey board

Announcements about the Altair 8800 Clone including software and hardware updates.

Altair Turnkey board

Postby AltairClone » September 5th, 2014, 4:16 pm

The Turnkey board for the Altair 8800 computer is implemented in the newest release of firmware for the Altair 8800 Clone (version 1.8).

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.
Since 0xFF is the sense switch port, booting from disk automatically enables all 64K of RAM because the boot loader PROM (while executing from RAM) does an IN operation from the sense switch port. Note that the Altair Multi-Boot Loader PROM (MBL) fails to run properly with the Turnkey board installed since this PROM reads the sense switch port while executing from PROM, effectively killing itself. If BASIC is loaded from paper tape or cassette with a bootstrap loader, it will also have access to a full 64K of RAM since BASIC reads the sense switches during initialization.

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
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Re: Altair Turnkey board

Postby jibanes » September 9th, 2014, 4:27 pm

Help me understand the capabilities added, this would make it possible to create a "startup script"?
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Re: Altair Turnkey board

Postby AltairClone » September 9th, 2014, 7:28 pm

The Turnkey module can make your computer automatically boot CP/M, for example, by simply turning on the computer. CP/M, in turn, can be configured to automatically run a script on cold and/or warm start. See the video http://youtu.be/RxrPmbsmyBs

Mike
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Re: Altair Turnkey board

Postby jibanes » September 10th, 2014, 3:27 pm

I see, awesome!
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