??????For EISA and PS/2, the code is issued after the test has passed, so a stuck code indicates the next test failed. Codes are sent to printer ports 3BC (the mono adapter's parallel port), 278, or 378; they will not be printed because no strobe data is sent. AT&Ts using the Olivetti motherboard and BIOS (e.g. the AT&T 6300) do the same. ????
??????Not a true IBM clone, as it had a Zilog Z8001 CPU. Also, a typical POST card will not fit in a slot, so you can only monitor codes from the parallel port. The POST shows a triangle, diamond, or 4 lines on the screen to indicate early POST failure, as shown in the table.
Program video controller using load, output, and jump relative instructions (need video).
Test Z8001 CPU registers and instructions; infinite loop if failure.
Test RAM module; infinite loop if failure; also send message to printer: E Mc bb ssss wwww. c = RAM configuration # (3 = 1 32K memory card); bb = hex 16K bank # (0,4,5,6,9,A=motherboard; 1,7,B=expansion board 1; 2=expansion board 2; 3,11,12=cxpansion board 3); ssss = what data should be; wwww = what data was (hex).
4 vertical lines
Test CPU call and trap instructions; infinite loop if failure.
Initialize screen and printer drivers.
Program USARTs (serial chips) and 8253 baud rate generator for keyboard at 1200 baud and RS232 at 9600. Now test remaining circuits and send codes to display and printer.