Restoring an IBM 5150 computer

Hi there, you are probably here because Google found some nice content about IBM 5150 and hardware. Well, that’s right, because I’m installing a MFM harddisk (Microscience HH-725) into a 5150 computer. In the picture you see the IBM that will get the harddisk.

I bought the hh-725 from a guy together with a controller. Actually 2 controllers of which one was defective.

To test the harddisk I connected it to another computer (also a 5150) which has the same harddisk. I disconnected the other HD and connected the “new” one. There was no C drive and when I started FDISK I got an error saying that there was no HD. I checked the dipswitches on the harddisks and found out that they were set different. I checked the internet for the manual. I set the switches correctly (if you want to know: 1 0 0 0 1 1 1 1 1 0). It’s 1 harddisk, all others should be terminated. And switch 10 is the exerciser: I tried it and it actually exercises the harddisk. It looks like it’s doing exercises (moving heads from a slow pace to a fast pace).

After doing this I tried again and nope, no C drive and FDISK now said something else: Error reading drive. hmmm. I think I have to lowlevel format it.

Most harddisk controllers have their own bios and with that bios (it’s just a program) it’s possible to lowlevel format a harddisk. The command to do this is quite hardcore if you ask me. These are the steps:

Lowlevel a harddisk on an IBM 5150 computer

1. boot DOS from a floppy
2. at the dosprompt: DEBUG <enter>
if you don’t have the DOS command DEBUG then make sure you find it on some other floppy (it was on the 3rd of my dosfloppies v4.1)
3. type: G=C800:5
4. you will see the screen next to this text. You will need to enter the information about the harddisk to lowlevel format it
5. use default values for items you can’t find in the manual.
The formatting took about 5 – 10 minutes. After that it asks “Do you want to format bad blocks”, answer no (type n and then press enter)
The harddisk is ready to be used. I booted from a floppy and then formatted the harddisk and added systemfiles to it by using the FORMAT command like this:
FORMAT c: /s

Update: I lowlevel formatted another disk (Seagate); I thought it could be useful to anyone:
Microscience HH-725: 612 4 613 613 11 5
Seagate ST-125: 615 4 616 616 11 5

The harddisk works fine and now it’s time to install it in the other computer. I removed the standard floppydrives and rearranged it a little. I tested both the controllers I bought and one of them works so I used that one.



After a while it looks nice and tidy. A final test and yes it works fine. OK,  close her up.





This is the final result. Looking great don’t you think. I installed Norton Commander, made an AUTOEXEC.BAT to set PATH and it’s ready to be used for funstuff 🙂




The defective controller gave an 1701 error at bootup, for more info about error codes of the IBM’s check this link

IBM 5150 mainboard switches

IBM 5150 findings

Hi there,

As a retro computer collector I’ve found out several things about those old computers. One of those is the IBM 5150. And sometimes it’s hard to find information about configuration and what’s possible and what’s not. So I will dedicate this post to findings for my (but also your) reference.

IBM 5150 mainboard dip switches

IBM 5150 mainboard switches
Large / big cursor when starting up?

I replaced a monochrome videocard with a color graphics card. If you turn on the IBM you will see a big cursor blinking and doing nothing else. You need to change the dip switches on your mainboard. Set dip switch 5 to ON. See schematic above.