There have been a number of questions recently regarding using different disks with a regular IBM-XT controller, so I thought I'd upload this infor- mation. I'm currently running a 10-meg & 20-meg disk on a Maynard controller whose rom is configured for 2 10-meg only. Only thing necessary was to change the table and point the vector to it with Bootcfg (in DL6). I use high-ram for the new table but have an old bios: this may not be so easy for others, but if your disk matches one of the existing tables below and you have an XT or PC with the IBM controller, all you should have to do is change switches. I've included the assembler file I use with Bootcfg at the end for reference. That code works ok even if executed AFTER dos initialization (assuming the disk parameters in the default table are sufficiently close to allow booting, or the disk you're installing isn't the one booted from). To be used that way, the code should be changed to org at 100h and be made into a .COM file with EXE2BIN. A jump to the code should be the first instruction, and the new tables should be placed before the code. That way you can do a terminate & stay resident call, leaving only the tables resident. I put conditional code in to illustrate this. Obviously the addresses will change if you're using the IBM fixed-disk bios, and you need to be familiar with assembler and know the specific parameters of your disk to get this working, but it's a relatively simple way to install practically any disk. If you have any questions, leave me a message on Compuserve PCS-131. -- Skip Gilbrech (71445,534) **************************************************************************** This is from PC Tech. Ref. dated Apr. '83 (says 2.02 on the cover), p. A-97 in the Fixed Disk Bios listing: FIXED DISK PARAMETER TABLE - The table is composed of a block defined as: (1 word) - max. number of cylinders (1 byte) - max. number of heads (1 word) - starting reduced write current cyl (1 word) - starting write precompensation cyl (1 byte) - max. ecc data burst length (1 byte) - control byte (drive step option) bit 7 disable disk-access retries bit 6 disable ecc retries bits 5-3 zero bits 2-0 drive option (seems to be step rate - sg) (1 byte) - standard time out value (see below) (1 byte) - time out value for format drive (1 byte) - time out value for check drive (4 bytes) - reserved for future use - To dynamically define a set of parameters build a table of values and place the corresponding vector into interrupt 41. Note: The default table is vectored in for an interrupt 19H (bootstrap). ON THE CARD SWITCH SETTINGS TRANSLATION TABLE DRIVE 0 DRIVE 1 1/3 : 2/4 : TABLE ENTRY ---------------------------- --------------------------- ON : / : ON : ON : 0 : -1- -2- / -3- -4- : ON : OFF : 1 OFF : / : OFF : ON : 2 ---------------------------- OFF : OFF : 3 DRIVE TABLES IN ROM (in above format, D = decimal, H = hex) TYPE 00 0306D 02D 0306D 0000D 0BH 00H 0CH 0B4H 028H 0,0,0,0 TYPE 01 0375D 08D 0375D 0000D 0BH 05H 0CH 0B4H 028H 0,0,0,0 TYPE 02 0306D 06D 0128D 0256D 0BH 05H 0CH 0B4H 028H 0,0,0,0 TYPE 03 0306D 04D 0306D 0000D 0BH 05H 0CH 0B4H 028H 0,0,0,0 **************************************************************************** (Following is the code I use to change my tables) **************************************************************************** page, 132 title LOADROM.ASM -- change hard disk parm table (used w/bootcfg.com) ;************************************************************************** ABS0 segment at 0 org 41h * 4 DISK_VECTOR label dword ; pointer to disk parameter tables ABS0 ends ;************************************************************************** MAYNARD segment at 0F400H org 700H MD_TBL label byte ; this is where Maynard's default tables are MAYNARD ends ;************************************************************************** BABY_BLUE segment at 0C000H org 0 BBD_TBL label byte ; this is where I put the new tables BABY_BLUE ends ;************************************************************************** DISKPARM_TBL struc ; Masm structure for the table described above MAX_CYL dw ? MAX_HEAD db ? RED_WRITE dw ? WRT_PRECMP dw ? ECC_BURST db ? CTRL_BYTE db ? TO_VAL db ? FTO_VAL db ? CDTO_VAL db ? RSVD db 4 dup (?) DISKPARM_TBL ends ;************************************************************************** FALSE equ 0 TRUE equ not FALSE .lfcond RESCOM equ FALSE ; make resident .COM file? ;RESCOM equ TRUE ;************************************************************************** CODE segment assume cs:CODE,ds:CODE if RESCOM org 100H endif START: if RESCOM jmp INIT ; jump to initialization code db 13 dup (?) ; start tables on para. boundary DKPT1 DISKPARM_TBL <> ; space for resident tables DKPT2 DISKPARM_TBL <> INIT: endif ; making resident .COM file push ds push es cli ; not while setting vectors cld ; mov ax,MAYNARD ; move the default tables to their mov ds,ax ; new home if not RESCOM mov ax,BABY_BLUE ; not necessary with .COM file mov es,ax ; mov di,offset BBD_TBL ; point to high-ram storage else mov di,offset DKPT1 ; point to local storage endif push di ; save ptr to table beginning mov si,offset MD_TBL ; point to default table mov cx,(type DISKPARM_TBL) ; size of table entry rep movsw ; use 'movsw' (moves both tables) pop di ; restore ptr to table beginning mov ax,612 ; new number of cylinders mov es:[di].MAX_CYL,ax ; change new copy of table mov es:[di].RED_WRITE,ax ; mov ax,ABS0 ; change vector to point to new tables mov es,ax if RESCOM mov word ptr es:DISK_VECTOR+2,cs mov word ptr es:DISK_VECTOR,offset DKPT1 else mov word ptr es:DISK_VECTOR+2,BABY_BLUE mov word ptr es:DISK_VECTOR,offset BBD_TBL endif sti pop es pop ds if RESCOM mov dx,offset INIT ; point after tables int 27H ; leave tables resident else ret endif CODE ends end START ; starting address for .COM file  er tables int 27H ; leave tables resident e