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Thread: VIC 1540 firmware ROM... original or not?

  1. #1

    Question VIC 1540 firmware ROM... original or not?

    I was given this drive a few months back and recently got to tinkering with it. I don't have a VIC20 right now (haven't had one since I was 7 years old) but I've done some reading and I see that these drives are really rare, especially if they have the original ROM.

    Can someone please tell me if this has been modified at all? I've searched online and I can't find any clear information about how to tell without running commands. I do have a C16 system as well, but I have no cables to connect the drive to the computer, and I don't know if they would work together anyway. If UAB4 and UAB5 are the ROMs, they don't look they've been replaced to me. They are marked 325302-01 and 325303-01 respectively. The serial number also seems lower than most that I've seen online.

    The forums are a bit limiting on picture size, so here are some pictures of the drive:
    https://photos.app.goo.gl/NLWwtpVjp4qrSKom7

    As always, any help is much appreciated.
    Last edited by Ozzuneoj; November 25th, 2020 at 12:22 PM.

  2. #2

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    Well, it seems I can't edit my post anymore. I just had another question, because the more I look online the more points to this having the original ROMs.

    Is there any way to test this drive on a Commodore 16 without doing the ROM replacement myself? I'd love to be able to test it at least. I'd just need to locate a cable for the drive.

  3. #3

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    325303-01 is the original drive ROM for the 1540, so that's the original ROM.

  4. #4

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    Quote Originally Posted by cihs View Post
    325303-01 is the original drive ROM for the 1540, so that's the original ROM.
    Cool, thank you!

    Is it possible to read disks at all with a C64 or C16 without the updated ROM? I'd like to test the drive, but I'd need to buy a cable. I don't really want to swap out the ROM to test it, because it's probably more interesting if it has never been modified at all.

    It's unlikely I'm going to stumble across a VIC20 any time soon.

  5. #5
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    Do the "TED" Commodores (C16 and Plus/4) have the same serial timing issue as the C64? If they don't then I'd think a 1540 would work with a C16, but I honestly have no idea.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  6. #6
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    With the original ROMs, I'm fairly certain you won't be able to use it with anything except a VIC-20.
    You can of course swap the ROMs temporarily with ROMs from a 1541.

    The C64 and 264 series (C16) both blank the screen during cassette loading for the same reason. They aren't fast enough to read data from the tape while the screen is stealing CPU cycles.
    I believe it's the same with the IEC serial data. The data rate is slower because the video chip is stealing CPU cycles.

    p.s. FWIW, you can only edit a post up to 1 hour after posting.

  7. #7
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    You could probably hook the load routines to blank the screen before loading and unblank afterwards. I'm sure a program like that exists somewhere... from the early days.

    It's more for bragging rights than actual use. It only goes with the VIC-20. Most of these were defective- the mechanisms are terrible and go out of alignment very easily.

  8. #8

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    Quote Originally Posted by Ozzuneoj View Post
    Cool, thank you!

    Is it possible to read disks at all with a C64 or C16 without the updated ROM? I'd like to test the drive, but I'd need to buy a cable. I don't really want to swap out the ROM to test it, because it's probably more interesting if it has never been modified at all.

    It's unlikely I'm going to stumble across a VIC20 any time soon.
    As others already said, those are the original 1540 ROMs.
    On a C64 you could try something like this:
    POKE 53265,PEEK(53265) AND 23:LOAD"$",8:POKE 53265,PEEK(53265) OR 16

    The pokes will first disable the screen display, then re-enable it after the load.
    I've never tried it since I obviously never had a 1540 (which is rare enough).

    Frank IZ8DWF

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