Debugging NEC Versa Series ROM BIOS 1.01.11, 04/19/90

bootlog.txt

via https://bochs.sourceforge.io/techspec/PORTS.LST
via https://docs.oracle.com/cd/E19121-01/sf.v40z/817-7184-12/post_codes.html

bios code: Copyright (C) 1985-1992 Phoenix Technologies Ltd.

cpuid
mov     %eax,%edx
shl     $0x10,%edx
ret

cli
mov     $0x80,%al
out     %al,$0x70 	;disable nmi

in      $0x92,%al
and     $-2,%al
out     %al,$0x92	;disable A20
cld

mov     $0x8f,%al
out     %al,$0x70
jmp     0
in      $0x71,%al
cmp     $11,%al		; 0B = return IRETS through 40:67
jne     0xf011c

in      $0x64,%al
test    $4,%al		; bit 2	 system flag status: 0=power up or reset  1=selftest OK

out     %al,$0x70
mov     $0,%al
out     %al,$0x71	; storing normal execution of post

			; acting on shutdown status byte

out     %al,$0xf1	; math coprocessor reset

			; Programmable Interrupt Controller 8259

			; yada-yada

mov     $0x43,%dx	; Programmable Interrupt Timer  8253, 8254
mov     $0x54,%al
out     %al,(%dx)	; PIT mode 2 select - rate generator

mov     $0x12,%al
out     %al,(%dx)	; PIT  counter 1, RAM refresh counter

mov     $0xc0,%al
out     %al,$0x80	; POST: Try to boot with interrupt 19

			; yada-yada

			; POST: Initialize error display function

			; yada-yada

			; reads 0x61: mirrors timer 2 output condition
			; awaits different values
			; messes up with EISA
			; im lost here