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Joined: 21 Dec 2005
Posts: 66

PostPosted: Thu Feb 02, 2006 4:26 am Reply with quoteBack to top

I found a beautiful old IBM PC AT about two years ago. It was in a rack-mount case, but this case was very odd - the top cover is constructed of Plexiglass, giving open views through the top, sides, and front panel. Definitely not shielded like it should be.

All of the cards inside were either original or IBM add-ons. The machine was configured with EGA (including the extra memory daughterboard), 1152KB RAM (512 motherboard, 640 on a card), monochrome/printer adapter, 1.2MB floppy, a full height MFM hard drive, IBM Token Ring, IBM 5250 Emulator card, and of course the drive controller.

It's a revision 1 motherboard using the stacked 128K modules and a 6Mhz clock, but the BIOS date is 11-85 ... (I would think that based on the BIOS date it would be an 8Mhz machine. I suspect the BIOS was updated.)

Sadly, the full height MFM hard drive was dead. The horrible screeching noise was my first clue.

I finally got around to working on the machine. Unable to find a suitable MFM drive, I decided to go IDE and replace the original controller with an IDE controller. The controller I had was a generic WinBond controller with a floppy adapter, serial and parallel ports. I had first started by trying to keep the original Western Digital drive controller in the machine for the floppy controller function, but I couldn't disable the hard disk controller function at all so it had to be replaced outright.

The new IDE controller did not have an onboard BIOS so I was limited to the 22 drive types that this machine knew, none of them more than 30 or 40MB. To fix the drive controller problem I added a Promise EIDEMAX, which adds a second IDE channel and has a BIOS capable of driving larger hard drives. (The Promise doesn't have a floppy port so I had to use both new cards ... arg!) Unfortunately, the Promise EIDEMAX froze the machine after finding the hard disk every time. I suspect it doesn't like the 6Mhz speed or the 80286 processor.

Finally I found an old version of OnTrack and installed that. The machine now is running the 635MB drive using OnTrack, which isn't great but it's better than pretending the 635MB drive is an ST-225. Smile DOS 5 is installed at the moment - I need to add a few more goodies.

What suprised me about the whole mess is that the IDE controller slipped into the place of the old full length Western Digital controller, and the machine didn't blink an eye. I later learned that the IDE interface is a superset of the ST506 - this means that the onboard BIOS of the machine is smart enough to drive it, even though IDE was invented many years after this machine was produced.

In retrospect next time I'm going to look for an IDE controller that has both an on-board BIOS (to do the drive CHS translation for large drive support) and floppy ports, so that I don't have to screw around with an EIDEMAX or Ontrack. The EIDEMAX was very disappointing .. freezing the machine up after finding the hard disk is anti-social.

Next step .. replace the IBM Token Ring card with an IBM EtherJet ISA card and get the thing on the network. After that, put NCSA Telnet and some other toys on there to make it somewhat usable.
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PostPosted: Thu Feb 02, 2006 3:30 pm Reply with quoteBack to top

a version of ontrack disk manager alone would work
or the shareware anydrive, that provides a drive overlay.
the 528 limit is 1024/16/63 and with some smaller than 528 ide drives has to be " jiggered" around to get full capacity.
meaning some smaller than 528 drives have more than 1024 cyl.
since most ide drives will translate a little math will permit one of the other numbers to be added to and the cyl set at 1024.
the generic phoenix setup.exe will likely work witrh the original IMB AT motherboard
some close clones of the ibm at would accept another, more advanced bios chipset.
but then it would not be a real IBM.
this might " get you" a system with setup in the bios- no disk based setup.
I have a box of original AT boards somewhere and a small box of award 286 bios' will have to try and see if they will work./

Joined: 21 Dec 2005
Posts: 66

PostPosted: Thu Feb 02, 2006 6:01 pm Reply with quoteBack to top

I used Ontrack by itself - I was not able to get the Promise EIDEMax to work. If I was able to make it work, then Ontrack would not be necessary. I don't like Ontrack as much, but given the lack of a working controller with a replacement BIOS extension, this is what I've got.

As for the system, it's just about as real as it gets except for the hard disk and controller now. And of course, I'm using the Diags disk to do the CMOS setup. Smile
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PostPosted: Thu Feb 02, 2006 8:41 pm Reply with quoteBack to top

there is likely no support for 1.44 drives, you will note thet it is not in the diage ibm diskette
the setup.exe from phoenix bios WILL set the drives, time, etc properly
but may have a 1.44 option that will frustrare you and not work.
it will see what ther drive table contains and set according to that.
but i think ontrack disk manager has set it at a default, type 1 or 2 and then does it's thing to permit use of more heads and cylinders.
I have some generic versions of dm.

heck I now I see who the author is.. you would know.

if you need parts and pieces let me know.
some are deeply buried but still should work.
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