BIOS data area

This is a partial map of the BIOS data area of the PS/1 model 2011.

12h	if bit0=1 skips memory test in POST 4F (F000:1229)
	if bit0=1 skips to POST 5B at POST 55 (F000:16E9)
	if bit0=1 skips POST beyond 6B into oblivion (F000:1C10)
	if bit0=1 exit func at F000:3159
	
15h	bit0=1 if VIDEO_INIT error (F000:1052) in POST 40
	bit1=1 if PIC error or unexpected interrupt at POST 42,43,44 (F000:10BA)
	       if RTC error (error 163, F000:2359)
	bit2=1 if COM1 error at POST 64 (F000:1A7C)
	bit3=1 if configuration error (error 161/162, POST 65 F000:1AE2)
	bit5=1 if memory size miscompare (error 164, POST 65 F000:1AF9)
	bit6=1 if ISA_ROM_CRC_FAIL (F000:32B3)
	       if SYSTEM ROM checksum error (POST 0B, F000:167A)

16h	bit1=1 if KB interface error (POST 59 F000:17B1)
	bit3=1 if KB Test input T0 is 1 after Disable keyboard command (POST 56 F000:1756)
	bit5=1 if error 301 (POST 59 F000:17BE)
	bit6=1 if floppy drive 0 fail / not installed (F000:1EAE)

64h

6Bh	set to 0 if PIC test passed at POST 43 (F000:10A4)
	this is a bitmask of IRQs which have occurred while the corresponding
	  interrupt vector points at the default system BIOS handler
	  (bit 0 = IRQ0 to bit 7 = IRQ7; bit 2 = IRQ8-15 on AT and later)
	  F000:23C6

72h	0064h during POST 23 if CMOS 16h Bit 6,7 != 11b (F000:0E38); Burn-in mode?
	      during POST 55 jump to POST 5B if is 64h (F000:16F3)
	0065h (coming from kb ctrl output buffer) during POST 25; manufacturing test mode
	00AAh tested for equality at POST 56 (F000:172A); if equal then skip keyboard anable
	5678h set at POST 6E (F000:1DEB); boot up the system
	9876h set at POST DD (F000:2E8F) if ROM error or not installed

90h	bit7 is bit7 of port 3F7h (!diskette change) (F000:1EDB)
	bit6 F000:3EA4
	bit5 F000:3EB0
	bit4 F000:3ECF
	bit0,1,2 = 40h:8Fh bit0,1,2 (drive0) or bit4,5,6 (drive 1) F000:3E8C
	         = 111 if 1.44MB, otherwise see MEM 0040h:0090h - DISKETTE DRIVE 0 MEDIA STATE