BIOS comments

devices/pc/bios/compaq/deskpro386/1988-01-28/1988-01-28.nasm

@@ -2297,52 +2297,55 @@ x91a1:	in	al,0x40			; 000091A1  E440  '.@'
 	pop	ax			; 000091AE  58  'X'
 	ret				; 000091AF  C3  '.'
 
-x91b0:	mov	dx,0x1f6		; 000091B0  BAF601  '...'
+;
-	mov	al,0xa0			; 000091B3  B0A0  '..'
+;   Here's where the first HDC (Hard Disk Controller) activity occurs during power-up.
-	out	dx,al			; 000091B5  EE  '.'
+;
-	call	xc5af			; 000091B6  E8F633  '..3'
+x91b0:	mov	dx,0x1f6		; 000091B0  select the DRVHD (Drive/Head) register
-	call	x83f9			; 000091B9  E83DF2  '.=.'
+	mov	al,0xa0			; 000091B3  select Head 0 (bits 0-3) and Drive 0 (bit 4)
-	mov	al,0xa8			; 000091BC  B0A8  '..'
+	out	dx,al			; 000091B5  write register
-	out	0x84,al			; 000091BE  E684  '..'
+	call	xc5af			; 000091B6  perform some I/O to the FDR (Fixed Disk Register), port 0x3F6
-	sti				; 000091C0  FB  '.'
+	call	x83f9			; 000091B9  TBD (writes 0xA0, 0xA1, 0xA2, 0xA3, 0xA6 to port 0x84)
-	mov	dx,0x3f4		; 000091C1  BAF403  '...'
+	mov	al,0xa8			; 000091BC
-	in	al,dx			; 000091C4  EC  '.'
+	out	0x84,al			; 000091BE
-	std				; 000091C5  FD  '.'
+	sti				; 000091C0
-	std				; 000091C6  FD  '.'
+	mov	dx,0x3f4		; 000091C1  select the REG_STATUS (Main Status Register) of the FDC
-	std				; 000091C7  FD  '.'
+	in	al,dx			; 000091C4  read register
-	std				; 000091C8  FD  '.'
+	std				; 000091C5
-	std				; 000091C9  FD  '.'
+	std				; 000091C6
-	std				; 000091CA  FD  '.'
+	std				; 000091C7
-	cld				; 000091CB  FC  '.'
+	std				; 000091C8
-	and	al,0xf			; 000091CC  240F  '$.'
+	std				; 000091C9
-	or	al,al			; 000091CE  0AC0  0x0A,'.'
+	std				; 000091CA
-	jz	x91d5			; 000091D0  7403  't.'
+	cld				; 000091CB
-	jmp	short x922a		; 000091D2  EB56  '.V'
+	and	al,0xf			; 000091CC  keep only the BUSY bits for drives A,B,C,D
+	or	al,al			; 000091CE  are any of those set?
+	jz	x91d5			; 000091D0  no
+	jmp	short x922a		; 000091D2  yes
+	nop				; 000091D4
 
-	nop				; 000091D4  90  '.'
+x91d5:	sub	sp,byte +0xd		; 000091D5
-x91d5:	sub	sp,byte +0xd		; 000091D5  83EC0D  '..',0x0D
+	mov	bp,sp			; 000091D8
-	mov	bp,sp			; 000091D8  8BEC  '..'
+	xor	ax,ax			; 000091DA
-	xor	ax,ax			; 000091DA  33C0  '3.'
+	mov	ds,ax			; 000091DC
-	mov	ds,ax			; 000091DC  8ED8  '..'
+	les	si,[0x78]		; 000091DE
-	les	si,[0x78]		; 000091DE  C4367800  '.6x.'
+	mov	ax,0x40			; 000091E2
-	mov	ax,0x40			; 000091E2  B84000  '.@.'
+	mov	ds,ax			; 000091E5
-	mov	ds,ax			; 000091E5  8ED8  '..'
+	mov	byte [0x40],0xff	; 000091E7
-	mov	byte [0x40],0xff	; 000091E7  C6064000FF  '..@..'
+	call	xca03			; 000091EC
-	call	xca03			; 000091EC  E81438  '..8'
+	mov	byte [bp+0x6],0x0	; 000091EF
-	mov	byte [bp+0x6],0x0	; 000091EF  C6460600  '.F..'
+	mov	byte [bp+0x7],0x0	; 000091F3
-	mov	byte [bp+0x7],0x0	; 000091F3  C6460700  '.F..'
+	call	x9293			; 000091F7  this executes a lot of instructions, but no HDC ports are accessed
-	call	x9293			; 000091F7  E89900  '...'
+	mov	byte [bp+0x6],0x1	; 000091FA
-	mov	byte [bp+0x6],0x1	; 000091FA  C6460601  '.F..'
+	call	x9293			; 000091FE  again, this executes a lot of instructions, but no HDC ports are accessed
-	call	x9293			; 000091FE  E89200  '...'
+	mov	byte [bp+0x5],0x0	; 00009201
-	mov	byte [bp+0x5],0x0	; 00009201  C6460500  '.F..'
+	call	xee9c			; 00009205
-	call	xee9c			; 00009205  E8945C  '..\'
+	mov	al,0xaf			; 00009208
-	mov	al,0xaf			; 00009208  B0AF  '..'
+	out	0x84,al			; 0000920A
-	out	0x84,al			; 0000920A  E684  '..'
+	mov	dx,0x3f2		; 0000920C  select the REG_OUTPUT (Digital Output Register) of the FDC
-	mov	dx,0x3f2		; 0000920C  BAF203  '...'
+	mov	al,0xc			; 0000920F  select the ENABLE and INT_ENABLE bits of REG_OUTPUT
-	mov	al,0xc			; 0000920F  B00C  '..'
+	out	dx,al			; 00009211  update register
-	out	dx,al			; 00009211  EE  '.'
+	and	byte [0x3f],0xf0	; 00009212
-	and	byte [0x3f],0xf0	; 00009212  80263F00F0  '.&?..'
+	add	sp,byte +0xd		; 00009217
-	add	sp,byte +0xd		; 00009217  83C40D  '..',0x0D
 	mov	al,0xb3			; 0000921A  B0B3  '..'
 	mov	ah,al			; 0000921C  8AE0  '..'
 	call	xb544			; 0000921E  E82323  '.##'
@@ -6670,10 +6673,18 @@ xbd0d:	in	al,0x64			; 0000BD0D  E464  '.d'
 	out	0x60,al			; 0000BD15  E660  '.`'
 	mov	al,0x25			; 0000BD17  B025  '.%'
 	out	0x84,al			; 0000BD19  E684  '..'
-	call	x91b0			; 0000BD1B  E892D4  '...'
+;
-	mov	al,0x26			; 0000BD1E  B026  '.&'
+;   Perform some FDC initialization
-	out	0x84,al			; 0000BD20  E684  '..'
+;
+	call	x91b0			; 0000BD1B
+
+	mov	al,0x26			; 0000BD1E
+	out	0x84,al			; 0000BD20
+;
+;   Perform some HDC initialization
+;
 	call	xc390			; 0000BD22  E86B06  '.k.'
+
 	mov	al,0x27			; 0000BD25  B027  '.',0x27
 	out	0x84,al			; 0000BD27  E684  '..'
 	mov	al,0xec			; 0000BD29  B0EC  '..'
@@ -7410,6 +7421,9 @@ xc388:	pop	si			; 0000C388  5E  '^'
 	shr	ax,cl			; 0000C38D  D3E8  '..'
 	ret				; 0000C38F  C3  '.'
 
+;
+;   HDC initialization
+;
 xc390:	mov	ax,0x40			; 0000C390  B84000  '.@.'
 	mov	ds,ax			; 0000C393  8ED8  '..'
 	mov	al,0xb0			; 0000C395  B0B0  '..'

devices/pc/bios/compaq/deskpro386/1988-01-28/makefile

@@ -2,14 +2,17 @@
 # Steps to produce a binary ROM from a JSON-encoded ROM, and then disassemble and re-assemble it.
 #
 
+FILEDUMP=node ../../../../../../modules/filedump/bin/filedump
+TEXTOUT=node ../../../../../../modules/textout/bin/textout
+
 all: 1988-01-28-test.rom
 
 1988-01-28.rom: 1988-01-28.json
-	node ../../../../../../modules/filedump/bin/filedump --file=1988-01-28.json --output=1988-01-28.rom --format=rom
+	$(FILEDUMP) --file=1988-01-28.json --output=1988-01-28.rom --format=rom
 
 1988-01-28-test.nasm: 1988-01-28.rom
 	ndisasm -o0x8000 -se105h -se05ah -se6ffh -sf025h -sf8aah 1988-01-28.rom > 1988-01-28-test.nasm
-	node ../../../../../../modules/textout/bin/textout --file=1988-01-28-test.nasm --nasm > temp.nasm
+	$(TEXTOUT) --file=1988-01-28-test.nasm --nasm > temp.nasm
 	mv temp.nasm 1988-01-28-test.nasm
 
 1988-01-28-test.rom: 1988-01-28-test.nasm