This page contains some useful tips and tricks for MCA-based PS/2 machines.
How to get out MCA-card IDs from IBM BASICA
Assumed you have a machine which refuses to boot from disk as well as from harddisk and you land in the IBM ROM-BASIC after pressing the [F1] function key.
Warning: MCA.DAT is a rather long file (>71KB) !
Then type the following BASIC program:
10 cls 20 for q=15 to 8 step -1 30 out(&H96),q 40 print q-7;": ";hex$(inp(&h101));"-";hex$(inp(&h100)) 50 next qPress [F2] to RUN the program.
The output will be a list starting with 8 and the Card-ID for the Slot #8 (uppermost in Mod. 80). On machines with only 3 or 4 slots only the lower are valid, all others will show FFFF. It might look like that:
8: 8E-FE (= IBM SCSI without cache) 7: F-1F (= Adaptec AHA-1640 SCSI) 6: E0-1 (= IBM 16/4 Mb/s Token Ring) 5: FF-FF 4: 8F-DA (= IBM XGA-2 Video) 3: FF-FF 2: FF-FF 1: FC-FF (= IBM 2-8MB 386 Memory)If the ID is i.e. 8E-FE the MCA.DAT-listing tells you it is the IBM SCSI-Adapter without cache. If the ID is for example F-1F the trailing 0 for the first half is missing and it is 0F1F. If the ID is E0-1 the trailing 0 for the last half is missing - look under E001. If the ID is FFFF the slot is empty.
How to determine / change FDD-type from BASIC
Assumed you have a machine which refuses to boot from floppy disk and probably from harddisk as well and you land in the IBM ROM-BASIC after pressing the [F1] function key.
OUT(&H70),&H10 PRINT HEX$(INP(&H71))The output should be 40, if there is only a drive A: installed and it is a 1.44MB-drive.
The first digit is the drive-type for A: (first FDD), the second digit is the drive-type for B: (second FDD).
Possible numbers are:
0 = not installed 1 = 360KB / 5.25 Inch 2 = 1.2MB / 5.25 Inch 3 = 720KB / 3.5 Inch 4 = 1.44MB / 3.5 Inch 6 = 2.88MB / 3.5 Inch 8 = Tape or reservedYou might change the type of drive with simply typing:
OUT(&h70),&H10 OUT(&H71),&H40But this might not help much if you landed into IBM ROM-BASIC. There is no way out from it into an operating system, because the operating system has not loaded. And -of course- you cannot access the FDD from out of ROM-BASIC.
After a reboot with [CTRL]+[ALT]+[DEL] the CMOS value might have got lost again. But it is worth trying ... in most cases the FDD accepts at least 720K-disks to boot from.