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Thread: Leading Edge Model M BIOS

  1. #21
    Join Date
    Jan 2007
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    Pacific Northwest, USA
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    I'm trying to follow this one. The BIOS file is 4000h bytes long or 16K, which implies a 27128 EPROM (28 pin).

    EGA and VGA are both supported by BIOS extensions on the video card, so it doesn't matter, so long as the BIOS supports extension ROMs (which it does). Only CGA and MDA/MGA don't require BIOS extension support.

    But then, maybe I'm being very dense and all of this has already been said.

  2. #22
    Join Date
    Sep 2017
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    No one else has the tech manual? I have it or something, but it's a mess, all mixed up with NCR docs. If someone has a scanner and promises to crank the stuff out in as short a time as possible ...

  3. #23

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    Ok, so I went to storage and pulled out the original manuals I have for the M, and on pg 183 of the technical manual it says to set SW1 5&6 to off, so all the online resources I found with Model M switch settings were wrong (I was changing SW2).

    So, With the BIOS upgrade to 4.71 and the switches set, the system boots up perfectly with the VGA card installed and no POST error codes.

  4. #24
    Join Date
    Mar 2013
    Location
    Chaffee, MO
    Posts
    1,144

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    hupshall,
    Yesterday , I dug out my old Leading Edge Model M, and checked it. I removed all the extra 8 Bit ISA boards, and the Hard Disk
    Controller. I connected the Tatung Monitor and powered it up. It powered up and read the Patched MSDOS 3.1 Floppy. Problem
    is I have no clue now what was patched on the 3.1 OS. I might have a note on the hard disk, and will check that today.

    In the bottom of the box I found the Original (bad copy) schematic pages I had purchased from Leading Edge, along with
    the SAMS Photofacts for the Model M. So, now I need to get all those scanned and preserved.

    Later in the evening I inserted the Hard Drive Controller, and it booted and came up. Hard Drive D: has been accidentally erased
    back in 2000, so it's likely gone forever. I might have copied it to a folder on some other hard drive, but so far I haven't located
    it. I'm still looking.

    There are jumper settings for 360 or 1.2m Floppy's right on the motherboard. JP9 - Drive 0 = A: 360 Default JP8 - Drive 1 = B:360 Default JP7 - NO Disk Change Default
    J9 - Jumper setting for Drive 0 = A:
    Pin 1-2 = 1.2M
    Pin 2-3 = 360K - Default

    J8 - Jumper setting for Drive 1 = B:
    Pin 1-2 = 1.2M
    Pin 2-3 = 360K - Default

    J7 - Jumper setting for Disk Change or No Disk Change
    Pin 1-2 = Disk Change
    Pin 2-3 = No Disk Change - Default

    There is also information about the Western Digital WD1002S-WX2Controller. I have a note at the bottom of page 2, that states to
    skip step 2, and just do this from within DEBUG:
    -G=C800:6 <Carriage RETURN> to initiate the Hard Drive format software.

    Thanks.

    Larry

  5. #25
    Join Date
    Mar 2013
    Location
    Chaffee, MO
    Posts
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    hupshall,
    I've got the Schematics scanned into .TIFF pages. Stitching the pages to make a 4 page panorama
    of the pages that match the original. It's taking a lot of time but I've got 2 of the 5 sections completed.
    I do a few pages each night watching TV.

    You can PM me if you want a complete copy, or just sections of the manual.

    One thing you MUST DO is remove that Nicad battery before it leaks and eats up your PCB.
    I was lucky. Mine was deab but had not leaked. I bought a replacement Lithium and now
    need to add a Diode in the charge circuit.

    Thanks.

    Larry

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