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Thread: AT&T PC6300 Storage Configuration

  1. #1
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    Default AT&T PC6300 Storage Configuration

    I acquired an AT&T PC6300 which is an XT-class machine, a rebranded Olivetti M24, in essence, and recently received timely and sage advice from several VCFED members, with whose help a puzzling issue (non-POST) was resolved.

    With the machine booting and having run customer diagnostics I would now like to address its remaining issues, the first of which is storage. The machine has only two 360K FDDs attached, and that's too small to do anything useful. I have used glitch's XT-IDE kits on an IBM 5160 and 5170 (using non-IBM ROMs) and I think that's an option that would work well here. But the AT&T BIOS, v.1.43, will only recognize lower density drives; 720k is the maximum the BIOS can address. One thought that has occurred to me is to swap one of the two FDDs with an HD-FDD (1.2 Mb) and drive both from an Adaptec 1542 ISA SCSI controller.

    With a little careful engineering there should be room for a SCSI hard drive as well, although at the cost of one or two motherboard slots. Maybe the XT-IDE can serve as the HD and not conflict with the 1542 controller. I'm not sure, and so I'm asking if anyone has experience with this approach.

    Thanks again!

    -CH-

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    I'm not sure I see the point of the 1542 when you can add faster, larger, cheaper, quieter storage with the XT-IDE coupled with a 4G compact flash card. And yes, the latest BIOS revision not only works fine in a 6300, but has some slight tweaks for 8086 systems for a hair more speed. Here's a thread with some testing and results: http://www.vcfed.org/forum/showthrea...012#post575012

    The 6300's floppy controller is onboard; SW7 and SW8 are supposed to control how many drives are connected, but I've never tried that. If you add XTIDE+CF storage, is there a need to put larger floppy drives in? Remember, most software that required delivery on 1.2MB floppies probably won't perform well on a 6300.
    Offering a bounty for:
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  3. #3

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    Quote Originally Posted by clh333 View Post
    I have used glitch's XT-IDE kits on an IBM 5160 and 5170 (using non-IBM ROMs) and I think that's an option that would work well here. But the AT&T BIOS, v.1.43, will only recognize lower density drives; 720k is the maximum the BIOS can address.
    Forget that BIOS. With 2M-XBIOS you can run a 1.44 MB floppy as the second floppy on anything.

    http://www.vcfed.org/forum/showthrea...577#post596577
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

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    Quote Originally Posted by Stone View Post
    Forget that BIOS. With 2M-XBIOS you can run a 1.44 MB floppy as the second floppy on anything.

    http://www.vcfed.org/forum/showthrea...577#post596577
    My word. Sorry, I missed the whole thread. Pays to ask, dunnit?

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    Quote Originally Posted by Trixter View Post
    If you add XTIDE+CF storage, is there a need to put larger floppy drives in? Remember, most software that required delivery on 1.2MB floppies probably won't perform well on a 6300.
    Thanks for the link. The point of having a 1.2 Mb 5.25 FD is for the sake of imaging disks of either lower or higher density. Dunfield and others caution about trying to use a 1.2 drive to write on 360k disks, and using a 360 drive to read or write 1.2 Mb disks is even harder.

    Being able to transfer the images by CF to a modern PC with twin TB drives and Internet access and wifi simplifies backup. That's part of why the XT-IDE makes sense. Yes, it's a sneaker-net at heart, but with a sneaker-net you don't have to worry about machine proximity, cabling or even common up-times.

    I want to enhance the performance of the AT&T without compromising the classic looks, I guess you could say.

    -CH-

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    Quote Originally Posted by Stone View Post
    Forget that BIOS. With 2M-XBIOS you can run a 1.44 MB floppy as the second floppy on anything.

    http://www.vcfed.org/forum/showthrea...577#post596577
    And get what? You can get standard 720K, but not 1.44M if the controller doesn't support the data rate. Sure, using oddball sector sizes, you can get more, but to what end? You can't read those floppies on other systems. And on those PCs with only a single floppy wired (LPC Southbridge Chipsets) you can use but a single floppy.

  7. #7

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    Quote Originally Posted by Chuck(G) View Post
    And get what? You can get standard 720K, but not 1.44M if the controller doesn't support the data rate. Sure, using oddball sector sizes, you can get more, but to what end? You can't read those floppies on other systems. And on those PCs with only a single floppy wired (LPC Southbridge Chipsets) you can use but a single floppy.
    Obviously, you must use a supported floppy controller.

    OP has a dual floppy system.

    I was replying to HIM, not the rest of the world-at-large.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

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    Well, for what it's worth, the FDC in the 6300 can be jumpered for 500K operation. See the motherboard schematic.

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    I agree with Jim that a CF + XT-IDE makes the most sense. As for floppy you may want to consider replacing one of the two 360k drives with a 3.5 floppy drive. It will only work at 720k, not 1.44Mb, but it will read and write disks that can be read and written with any other 3.5 drive, including cheap USB ones like this one: https://www.amazon.com/External-Port.../dp/B00WSW1YXA

    This way you have a quick and easy way of moving small files from a modern machine to the 6300 without even turning the power off (which you would need to do to swap out the CF). And you can get it in black with matching black 5.25 to 3.5 bay adapter so it wont spoil the look

    As for 1.2Mb drives, as you say they are a source of problems when dealing with 360k disks. They will (usually) read them, but wont write them in a way that makes them readable in 360k drives, in my experience. Also its a bit academic - they wont work in a 6300 with the built-in controller. They are my least favourite floppy disk format

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    Quote Originally Posted by Valerio View Post
    As for 1.2Mb drives, as you say they are a source of problems when dealing with 360k disks. They will (usually) read them, but wont write them in a way that makes them readable in 360k drives, in my experience. Also its a bit academic - they wont work in a 6300 with the built-in controller. They are my least favourite floppy disk format
    Well, not quite. It's possible to jumper (on the mainboard) the FDC to run at 8MHz instead of 4, thereby creating 500KHz as the basic clock for data instead of 250KHz. The problem is that you can then only use high-density drives, as the data rate isn't software selectable.

    See P13 of the schematic, note the jumper on the left labeled JPR-SPDT that selects between 8 and 4 MHz. For that matter, you could drive a couple 8" floppies--or HD 3.5" ones.

    You did say that 1.2M drives wouldn't work...

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