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Thread: Olivetti M24/AT&T 6300 bus converter necessary?

  1. #1

    Question Olivetti M24/AT&T 6300 bus converter necessary?

    Hi there,

    As there seems to be a lot of great knowledge of these machines in these forums, I thought I might try my luck.
    I recently got my childhood M24 in working order again, and now it's time to upgrade it a bit. It's a version without HDD and bus converter. I mainly want to add an XT-IDE.
    Bus converters are pretty hard or expensive to come by. By looking through the "Theory of Operation" manual (pages B-29, B-35), it looks to my not very savvy eyes, as if the connector for the bus converter is just a single ISA slot itself. The pin-out of the connector seems to be the same as the slots on the bus converter.
    My question is, would it be possible to directly plug one single ISA card into the connector itself, without the use of the converter?

    Thanks a lot!

  2. #2
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    Hmm, I was under the impression those two were essentially the same thing. As I understand it, there is a known compatiblity issue with the high-speed aka "chuck-mod" mode but otherwise, they can work.

  3. #3
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    The bus converter is not necessary, and you can use an XT-IDE just fine in compatibility mode. I recently successfully tested a glitchworks v4 board with the very latest XT-IDE Universal BIOS and it worked in my M24/6300: http://www.vcfed.org/forum/showthrea...ht=#post575012
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  4. #4

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    Thank you both very much!
    Now my XT-IDE kit just needs to get through customs. It's been sitting there for two weeks. But RAM is also on they way to upgrade from 256K to 640K, so I have something to play with while I wait.
    Sorry to hear you broke a 6300 for science. I hope you get it working again!

  5. #5

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    Well, turns out for the XT-IDE kit I need the bus converter, or at least some ISA extender, as the capacitor is to high and I can't get the board into the socket.

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    Can you post pictures? I've put several different models of XT-IDE cards (lo-tech, glitch v4) into my 6300 without any problems with them fitting into the slot...?
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  7. #7

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    Thanks. Maybe I'm doing something obviously wrong.
    I've attached one view from above. The slot and the connector are almost flush. And yes, the machine could need some more cleaning. You can see the capacitor causing the problem in another picture. I've (roughly) measured the distance from the case bottom to the center of the slot at 7mm, from the top of the capacitor to the center of the PCB it's 11mm.

    IMG_20190720_014408.jpgIMG_20190720_014953.jpgIMG_20190720_014532.jpg

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    I misunderstood; when you wrote "bus converter" I thought you meant the "bus conversion kit" which is something else. Yes, you need the bus converter to use an M24/6300.

    An M24/6300 has two mandatory pieces: A motherboard, and a bus converter. The ISA cards go into the bus converter; the bus converter connects to the motherboard. There are more detailed pictures in the second half of this video at 12:40: https://youtu.be/mUCh46_MzZU

    Since an M24 is not usable without the bus converter board, how did you obtain a computer without one?
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  9. #9

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    Yes, I know what it looks like. I just asked because the connector on the graphics card, where the bus connectors goes in, seems to be identical to an ISA slot according to my layman eyes when looking through the "Theory of Operations" manual.

    My father brought the M24 home in the late eighties because the company where he worked didn't need it anymore. Why it doesn't have a converter, I don't know. But not all models were sold with a converter installed. For example the DATEV version. That often came without a bus converter, but had a special DATEV keyboard (keyboard 3) and DATEV stickers on the case, which I don't have. Apparently the DATEV model only had an angled adapter for one ISA slot when you bought the hard disk version.

    Anyway, I ordered a bus converter from ebay for $44, plus way too much for ebay's international shipping rip-off scheme, and it should be here in early August. Do you have any tipps on what I could use to mount it in the case? I obviously don't have the original mounting "thingies" that go between the converter and the metal plate and I doubt my converter will come with them.

  10. #10
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    Never knew it was sold without the bus converter -- seems very strange. Thanks for the info. As for mounting it, I would start with cardboard spacers to get a feel for the spacing, and then I'm not sure -- 3-d printing, maybe? I don't recall if they used standard standoffs but being 1983 they likely don't.
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

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