memory.lst

A Programmer s Reference to BIOS, DOS, and Third-Party Calls

	  is powered up.
SeeAlso: MEM 0040h:006Ch,INT 1A/AH=00h
--------K-M00400071--------------------------
MEM 0040h:0071h - Ctrl-Break FLAG
Size:	BYTE
Desc:	bit 7 is set when Ctrl-Break has been pressed
SeeAlso: INT 1B
----------M00400072--------------------------
MEM 0040h:0072h - POST RESET FLAG
Size:	WORD
Desc:	specify the action the BIOS should take at the beginning of the
	  power-on self-test when the machine is reset
SeeAlso: INT 19,MEM F000h:FFF0h

(Table M0021)
Values for POST reset flag:
 0000h	cold boot
 0064h	Burn-in mode
 1234h	to bypass memory test (warm boot)
 4321h	[PS/2 except Mod 25,30] to preserve memory
 5678h	[Conv] system suspended
 9ABCh	[Conv] manufacturing test mode
 ABCDh	[Conv] POST loop mode
--------B-M00400074--------------------------
MEM 0040h:0074h - FIXED DISK LAST OPERATION STATUS (except ESDI drives)
Size:	BYTE
SeeAlso: INT 13/AH=01h,INT 13h/AH=0Ah,MEM 0040h:0041h

(Table M0022)
Values for fixed disk last operation status:
 00h	no error
 01h	invalid function request
 02h	address mark not found
 03h	write protect error
 04h	sector not found
 05h	reset failed
 06h	diskette removed
 07h	drive parameter activity failed
 08h	DMA overrun
 09h	DMA data boundary error
 0Ah	bad sector flag detected
 0Bh	bad track detected
 0Ch	requested diskette media type not found
	(PS/2 or extended BIOS only) unsupported track
 0Dh	invalid number of sectors for Format
 0Eh	control data address mark detected
 0Fh	DMA arbitration level out of range
 10h	uncorrectable ECC or CRC error
 11h	ECC corrected data error
 20h	general controller failed
 40h	seek failed
 80h	time out
 AAh	drive not ready
 B0h	volume not locked in drive (INT 13 extensions)
 B1h	volume locked in drive (INT 13 extensions)
 B2h	volume not removable (INT 13 extensions)
 B3h	volume in use (INT 13 extensions)
 B4h	lock count exceeded (INT 13 extensions)
 B5h	valid eject request failed (INT 13 extensions)
 BBh	undefined error
 CCh	write fault on selected drive
 E0h	status error/error register is zero
 FFh	sense failed
SeeAlso: #00234
--------d-M00400074--------------------------
MEM 0040h:0074h - WD1002-27X SuperBIOS - TOTAL DRIVES, FIRST CONTROLLER ONLY
Size:	BYTE
SeeAlso: MEM 0040h:0075h"SuperBIOS",MEM 0040h:0076h"SuperBIOS"
--------B-M00400075--------------------------
MEM 0040h:0075h - FIXED DISK - NUMBER OF FIXED DISK DRIVES
Size:	BYTE
SeeAlso: MEM 0040h:0076h"FIXED DISK",MEM 0040h:0077h"FIXED DISK"
--------d-M00400075--------------------------
MEM 0040h:0075h - WD1002-27X SuperBIOS - TOTAL FIXED DRIVES, BOTH CONTROLLERS
Size:	BYTE
SeeAlso: MEM 0040h:0074h"SuperBIOS",MEM 0040h:0076h"SuperBIOS"
--------B-M00400076--------------------------
MEM 0040h:0076h - FIXED DISK - CONTROL BYTE    {IBM documented only for XT}
Size:	BYTE
Desc:	loaded from the disk parameter table control byte (offset 8) during
	  various hard disk operations
SeeAlso: MEM 0040h:0075h"FIXED DISK",MEM 0040h:0077h"FIXED DISK"
--------d-M00400076--------------------------
MEM 0040h:0076h - XT: hard disk controller's I/O address (Western Digital)
Size:	BYTE
--------d-M00400076--------------------------
MEM 0040h:0076h - WD1002-27X SuperBIOS - USED IN TRACK RECALCULATION
Size:	BYTE
SeeAlso: MEM 0040h:0074h"SuperBIOS",MEM 0040h:0075h"SuperBIOS"
SeeAlso: MEM 0040h:0077h"SuperBIOS"
--------B-M00400077--------------------------
MEM 0040h:0077h	- FIXED DISK - I/O port offset {IBM documented only for XT}
Size:	BYTE
SeeAlso: MEM 0040h:0075h"FIXED DISK",MEM 0040h:0076h"FIXED DISK"
--------d-M00400077--------------------------
MEM 0040h:0077h - WD1002-27X SuperBIOS - USED IN TRACK RECALCULATION
Size:	BYTE
SeeAlso: MEM 0040h:0076h"SuperBIOS"
--------B-M00400078--------------------------
MEM 0040h:0078h - PARALLEL DEVICE 1 TIME-OUT COUNTER
Size:	BYTE
Note:	Under DR-OpenDOS 7.02+ this setting can be changed with the
	  undocumented CONFIG.SYS LPT1=[port_address|logical_no][,[timeout]]
	  directive, whereby port_address = 200h..3FCh, logical_no = 0 or 1..3,
	  timeout=0..255 (default 20).
SeeAlso: MEM 0040h:0079h,MEM 0040h:007Ah,INT 17/AH=00h
--------B-M00400079--------------------------
MEM 0040h:0079h - PARALLEL DEVICE 2 TIME-OUT COUNTER
Size:	BYTE
Note:	Under DR-OpenDOS 7.02+ this setting can be changed with the
	  undocumented CONFIG.SYS LPT2=[port_address|logical_no][,[timeout]]
	  directive, whereby port_address = 200h..3FCh, logical_no = 0 or 1..3,
	  timeout=0..255 (default 20).
SeeAlso: MEM 0040h:0078h,MEM 0040h:007Ah,INT 17/AH=00h
--------B-M0040007A--------------------------
MEM 0040h:007Ah - PARALLEL DEVICE 3 TIME-OUT COUNTER
Size:	BYTE
Note:	Under DR-OpenDOS 7.02+ this setting can be changed with the
	  undocumented CONFIG.SYS LPT3=[port_address|logical_no][,[timeout]]
	  directive, whereby port_address = 200h..3FCh, logical_no = 0 or 1..3,
	  timeout=0..255 (default 20).
SeeAlso: MEM 0040h:0078h,MEM 0040h:0079h,MEM 0040h:007Bh"PARALLEL"
--------B-M0040007B--------------------------
MEM 0040h:007Bh - PARALLEL DEVICE 4 TIME-OUT COUNTER (pre-PS, PS Models 25,30)
Size:	BYTE
Note:	Under DR-OpenDOS 7.02+ this setting can be changed with the
	  undocumented CONFIG.SYS LPT4=(port_address|logical_no)[,[timeout]]
	  directive, where port_address = 200h..3FCh, logical_no = 0 or 1..3,
	  timeout=0..255 (default 20).  To avoid any interference with the PS/2
	  and later interpretation, this will be rejected if this entry does
	  not hold 0, which would indicate it is used for different purposes.
SeeAlso: MEM 0040h:0078h,MEM 0040h:007Ah,MEM 0040h:007Bh"INT 4Bh"
--------m-M0040007B--------------------------
MEM 0040h:007Bh - INT 4Bh FLAGS (PS2 and newer)
Size:	BYTE
SeeAlso: INT 4B/AX=8102h

Bitfields for INT 4Bh flags:
Bit(s)	Description	(Table M0023)
 7-6	reserved
 5	set if Virtual DMA Spec supported [PS] (see INT 4B)
 4	reserved
 3	set if INT 4Bh intercepted and must be chained
 2	reserved
 1	set if Generic SCSI CBIOS services available on INT 4Bh
 0	reserved
--------B-M0040007C--------------------------
MEM 0040h:007Ch - SERIAL DEVICE 1 TIMEOUT COUNTER
Size:	BYTE
Note:	Under DR-OpenDOS 7.02+ this setting can be changed with the
	  undocumented CONFIG.SYS COM1=[port_address|logical_no][,[timeout]]
	  directive, whereby port_address = 200h..3F8h, logical_no = 0 or 1..4,
	  timeout=0..255 (default 1).
SeeAlso: MEM 0040h:0000h,MEM 0040h:007Dh,MEM 0040h:007Eh,MEM 0040h:007Fh
SeeAlso: INT 14/AH=01h
--------B-M0040007D--------------------------
MEM 0040h:007Dh - SERIAL DEVICE 2 TIMEOUT COUNTER
Size:	BYTE
Note:	Under DR-OpenDOS 7.02+ this setting can be changed with the
	  undocumented CONFIG.SYS COM2=[port_address|logical_no][,[timeout]]
	  directive, whereby port_address = 200h..3F8h, logical_no = 0 or 1..4,
	  timeout=0..255 (default 1).
SeeAlso: MEM 0040h:0002h,MEM 0040h:007Ch,MEM 0040h:007Eh,MEM 0040h:007Fh
SeeAlso: INT 14/AH=01h
--------B-M0040007E--------------------------
MEM 0040h:007Eh - SERIAL DEVICE 3 TIMEOUT COUNTER
Size:	BYTE
Note:	Under DR-OpenDOS 7.02+ this setting can be changed with the
	  undocumented CONFIG.SYS COM3=[port_address|logical_no][,[timeout]]
	  directive, whereby port_address = 200h..3F8h, logical_no = 0 or 1..4,
	  timeout=0..255 (default 1).
SeeAlso: MEM 0040h:0004h,MEM 0040h:007Ch,MEM 0040h:007Dh,MEM 0040h:007Fh
SeeAlso: INT 14/AH=01h
--------B-M0040007F--------------------------
MEM 0040h:007Fh - SERIAL DEVICE 4 TIMEOUT COUNTER
Size:	BYTE
Note:	Under DR-OpenDOS 7.02+ this setting can be changed with the
	  undocumented CONFIG.SYS COM4=[port_address|logical_no][,[timeout]]
	  directive, whereby port_address = 200h..3F8h, logical_no = 0 or 1..4,
	  timeout=0..255 (default 1).
SeeAlso: MEM 0040h:0006h,MEM 0040h:007Ch,MEM 0040h:007Dh,MEM 0040h:007Eh
SeeAlso: INT 14/AH=01h
--------K-M00400080--------------------------
MEM 0040h:0080h - KEYBOARD BUFFER START OFFSET FROM SEGMENT 40h (normally 1Eh)
Size:	WORD
SeeAlso: MEM 0040h:001Ah,MEM 0040h:001Eh,MEM 0040h:0082h,INT 16/AH=05h
--------K-M00400082--------------------------
MEM 0040h:0082h - KEYBOARD BUFFER END+1 OFFSET FROM SEGMENT 40h (normally 3Eh)
Size:	WORD
Note:	XT BIOS dated 11/08/82 ends here
SeeAlso: MEM 0040h:001Ch,MEM 0040h:003Eh,MEM 0040h:0080h,INT 16/AH=05h
--------V-M00400084--------------------------
MEM 0040h:0084h - VIDEO (EGA/MCGA/VGA) - ROWS ON SCREEN MINUS ONE
Size:	BYTE
SeeAlso: MEM 0040h:0085h,INT 10/AX=1100h
--------V-M00400085--------------------------
MEM 0040h:0085h - VIDEO (EGA/MCGA/VGA) - CHARACTER HEIGHT IN SCAN-LINES
Size:	WORD
SeeAlso: MEM 0040h:0084h,INT 10"LIRVGA19"
!!!
--------V-M00400087--------------------------
MEM 0040h:0087h - VIDEO (EGA/VGA) CONTROL: [MCGA: =00h]
Size:	BYTE
SeeAlso: MEM 0040h:0084h,MEM 0040h:0085h,MEM 0040h:0088h

Bitfields for EGA/VGA Video control flags:
Bit(s)	Description	(Table M0024)
 7	do not to clear RAM on mode set (see INT 10h, AH=00h)
 6-5	RAM on adapter = (this field + 1) * 64K
 4	reserved
 3	EGA/VGA video system INactive
 2	wait for display enable
 1	mono monitor
 0	alphanumeric cursor emulation DISabled
	When enabled, text mode cursor size (INT 10,AH=01h) settings looking
	 like CGA ones are translated to equivalent EGA/VGA ones.
--------V-M00400088--------------------------
MEM 0040h:0088h - VIDEO (EGA/VGA) SWITCHES: [MCGA: reserved]
Size:	BYTE
SeeAlso: MEM 0040h:0087h,MEM 0040h:0089h

Bitfields for EGA/VGA Video switches:
Bit(s)	Description	(Table M0025)
 7-4	power-on state of feature connector bits 3-0
 3-0	configuration switches 4-1 (=0 on, =1 off) (see #M0026)
Note:	when bit 4 of 0040h:0089h is 0, VGA emulates 350-line EGA if this
	  byte is x3h or x9h, otherwise emulates 200-line CGA in 400-line
	  double scan. VGA resets this byte to x9h after the mode set.
	See also note for 0040h:0089h.

(Table M0026)
Values for EGA/VGA configuration switches:
 00h Pri MDA,				Sec EGA+old color display 40 x 25
 01h Pri MDA,				Sec EGA+old color display 80 x 25
 02h Pri MDA,				Sec EGA+ECD normal mode (CGA emul)
 03h Pri MDA,				Sec EGA+ECD enhanced mode
 04h Pri CGA 40 x 25,			Sec EGA mono display
 05h Pri CGA 80 x 25,			Sec EGA mono display
 06h Pri EGA+old color display 40 x 25, Sec MDA
 07h Pri EGA+old color display 80 x 25, Sec MDA
 08h Pri EGA+ECD normal mode (CGA emul), Sec MDA
 09h Pri EGA+ECD enhanced mode,		Sec MDA
 0Ah Pri EGA mono display,		Sec CGA 40 x 25
 0Bh Pri EGA mono display,		Sec CGA 80 x 25
SeeAlso: #M0025
--------b-M00400088--------------------------
MEM 0040h:0088h - Olivetti EGA capabilities???
Size:	BYTE???

Bitfields for Olivetti EGA capabilities flags:
Bit(s)	 Description	(Table M0130)
 7	 640x400 mode related???
 6	 unknown
 5	 640x400 mode related???
 4-0	 unknown
Note:	To decide if the 640x400 mode is supported by an Olivetti EGA card
	  (only the Olivetti EGA card 2 supports it), also check that bit 7
	  and 5 are set.
SeeAlso: C000h:0000h"Olivetti"
--------V-M00400089--------------------------
MEM 0040h:0089h U - VIDEO (MCGA/VGA) - MODE-SET OPTION CONTROL
Size:	BYTE
SeeAlso: MEM 0040h:0087h,MEM 0040h:0088h

Bitfields for Video mode-set option control:
Bit(s)	Description	(Table M0027)
 7,4	requested scan lines
	0 0  350-line mode requested
	0 1  400-line mode at next mode set
	1 0  200-line mode requested
	1 1  reserved
	Note:	Apparently VGA BIOS mode set disregards bit 7 and uses
		  byte 40h:88h to determine 200/350 selection when bit 4
		  is zero. Presumably bit 7 is a convenience for other
		  purposes. Bit 7 is reset to zero after the mode set.
 6	display switching enabled
 5	reserved
 4	if set:	  use 400-line mode at next mode set
	if clear: [VGA] emulate EGA at next mode set
		[MCGA] emulate CGA, digital monitor, 200 lines, 8x8 text
	Note: this bit is set by the video mode set on VGA, unchanged on MCGA
 3	default palette loading DISabled at mode set
 2	mono display
 1	gray scale summing enabled
 0	[VGA] =1 if VGA active, =0 if not
	[MCGA] reserved, zero
Note:	the Tseng ET4000 BIOS v3.00 uses bits 6-4 of 88h and bits 6-5 of 89h
	  to specify graphics-mode refresh rates as follows
		88h/6		640x480:  1 for 72Hz,0 for 60Hz
		88h/5+89h/6	800x600:  00  60Hz
					  01  56Hz
					  11  72Hz
		88h/4+89h/5	1024x768: 00  interlaced
					  01  60Hz
					  10  72Hz???
					  11  70Hz
--------V-M0040008A--------------------------
MEM 0040h:008Ah U - VIDEO (MCGA/VGA) - INDEX INTO DISPLAY COMBINATION CODE TBL
Size:	BYTE
SeeAlso: INT 10/AX=1A00h,#M0039
--------*-M0040008B--------------------------
MEM 0040h:008Bh - PC, PCjr, PC/XT 11/8/82, Convertible - RESERVED
Size:	11 BYTEs
--------B-M0040008B--------------------------
MEM 0040h:008Bh - DISKETTE MEDIA CONTROL
Size:	BYTE

Bitfields for diskette media control:
Bit(s)	Description	(Table M0028)
 7-6	last data rate set by controller
	00=500kbps, 01=300kbps, 10=250kbps, 11=1Mbps
 5-4	last diskette drive step rate selected
	00=0Ch, 01=0Dh, 10=0Eh, 11=0Ah
 3-2	{data rate at start of operation}
 1-0	reserved
Note:	EHD BIOS sets this byte to 01h and never reads it back
--------B-M0040008C--------------------------
MEM 0040h:008Ch - FIXED DISK - CONTROLLER STATUS [not XT]
Size:	BYTE
SeeAlso: MEM 0040h:008Dh,MEM 0040h:008Eh
--------B-M0040008D--------------------------
MEM 0040h:008Dh - FIXED DISK - CONTROLLER ERROR STATUS [not XT]
Size:	BYTE
SeeAlso: MEM 0040h:008Ch,MEM 0040h:008Eh
--------B-M0040008E--------------------------
MEM 0040h:008Eh - FIXED DISK - INTERRUPT CONTROL [not XT]