IMSAI 8080 30 years since last powerup

[hansn]

Just started restoring an old 8080; power supply being tested (for Australia); I have a mod called “optional CPA Revision 4 or Earlier CPA boards to change power switch to write protect/unprotect switch for use with RAM 4A boards; can anyone help me understand this mod?

 

[griffk]

Yes, you have the optional mod (ECO) that allows the 2 position power switch to be replaced with a 3 pole momentary, to toggle the PROTECT bit on the RAM 4A bd.

This mod allows you to toggle PROTECT/UNPROTECT for the currently addressed block of memory on the RAM 4A, and to change the HOLD LED to a PROTECT LED (PROTECT=ON, memory addressed-protected), on the front panel.