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IBM ESDI Hard Drive Replacement


New Member
Jan 29, 2019
Los Estados Unidos
I recently posted on this forum about my attempt at repairing an IBM PS/2 50Z. This endeavor has hit a roadblock, that is that the hard disk in the machine will not work. Any attempt at formatting the drive results in a "Disk unusable" message from MS-DOS. Is there any way that this drive could be replaced? I would prefer something like an IDE hard drive adapter or SD card adapter but there seems to be little information online pertaining to these machines.
I had the same problem and I gave up and got rid of the machine. You’re probably better off finding a scsi card, but finding one at an affordable price will be hard.
That's a microchannel system, right? Hard to get any controller card for it...

I would give a chance to the harddribe. Maybe, like on floppy drives, it helps to replace all capacitors...?
The PS/2 Model 50Z doesn't use ESDI. It uses a proprietary "Direct Bus Attachment" (DBA) hard drive interface.

Like many things involving the PS/2, the original hard drives and interface circuitry suffer from failing electrolytic capacitors. Replacing them may get yours going again.

There were SCSI and IDE controller cards made for the Microchannel bus, but good luck finding one these days...
IPL = Initial Program Load -- an old-school term from the mainframe computer era. That error basically just means that the drive isn't bootable.
I think "IPL" was S/360+ IBMish. Older systems, IIRC, just called it "Program Load" or something to that effect.
CDC used "deadstart"
Univac used "bootstrap", IIRC.
Burroughs was a bit peculiar; it had "Cold Start" and "Cool Start"

This is all from memory.
Ok so I recapped the drive. Now the system is giving a 113 error during testing the hard drive test on the ref disk, and it occasionally will only boot to a black screen (no memory count even)
So with all the advances and having a working replacement to the XT8bit IDE drives using the pi pico do you think a working ESDI replacement might be on the horizon? My IBM P70 is uselesa without an hdd.
do you think a working ESDI replacement might be on the horizon?

tubetimeus is working on a DBA replacement.
he has it mostly working in a Thinkpad 700
Not sure. Im speaking specifically of the hard drive in My IBM P70 which all documents seem to refer toas ESDI. What does ESDI mean to you?
The ESDI interface was an advancement of the standard ST-506 interface and was often used for higher capacity drives (>=150MB). I never used them with PS/2 rather ISA based Server PCs.
I also produced a microchannel card back in the day, to simplify matters we used a microchanel interface LSI IC to do so.