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Thread: XT Clone Troubleshooting mystery.

  1. #1

    Default XT Clone Troubleshooting mystery.

    I have a bit of a mystery issue with an XT clone.

    The machine is a Juko XT turbo clone with IBM cards.This is the board https://stason.org/TULARC/pc/motherb...XT-BXM-12.html
    I also have an exact twin to it, both machines were true IBM's when purchased in the 80's and the main boards were both replaced at the same time in 1989 keeping the original IBM cards in the XT 5160 case.

    I was messing around with a batch of floppies I purchased and one of them was a copy of King's Quest. I proceeded to try and boot it. The machine came to the title screen and when you hit the space bar to continue the machine went to access the drive and froze up still playing the last musical note Beeeeeeeeeeeeeeeeeeeeeeeeeeeeep till I turned it off. Thinking its probably a bad disk since it was accessing the drive when it crashed I gave it a twirl in its twin. It booted up fine and went right into the game and played just fine in the other machine no issues.

    So wanting to know whether if it was the disk or a memory problem I tried it again in the first machine and same result machine froze up same spot after the title screen while loading the game.
    Figuring now it was probably memory going bad I ran Check-it and it passed all the tests.
    To be thorough I swapped the floppy drives figuring possibly the drive might have an issue.. Same crash in same spot
    Swapped the CGA cards.. Same crash in same spot
    So I ran Check-it on memory for most of the day no issues..
    Tried a different program I stuck MS Flightsim 1.05 its a booter disk it loaded and ran fine no issues.
    Then I tried a different copy of King's Quest that I have in my collection already its actually an older booter version like Flightsim runs on its own wierd OS and it had slightly better success than the first on.. it came to the title screen then when you hit space bar to continue it would load the game.. draw the castle put the character on the screen, flags waving, croc's swimming but the second you try to move the character "Freeze" and stuck on the last noise being played till you shut it off.
    I tested the second disk in the twin and it also just played fine.
    So tried a few other games and discovered thru trial and error this machine "HATES" JUST Sierra games and it happens all in all of them in about the same spot after the title and just before the actual game play commences, if you move the character it locks up. The machine played Lode Runner, Night mission pinball, and a bunch of other NON Sierra games just fine. And its twin plays ALL of them fine.

    The interesting thing is some of the Sierra games have animated titles like Donald Duck, KQII and LSL you'd think it would lock up if it was just the animation but it only locks up on the start of game play and only in Sierra games

    I have swapped everything between the two machines except the chips on the motherboard which I might try this weekend.
    Anybody ever come across a machine that hates a particular software company?? LOL!! This is really a wierd one!! Any suggestions??

  2. #2
    Join Date
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    Default

    Are the motherboards really identical? The first thing that comes to mind when I see a program that fails on an otherwise working motherboard is the BIOS. A different BIOS revision could easily cause problems like this.

    A particular author or company could try to use a BIOS call in some way that happens to work on a genuine IBM, but wasn't clearly documented anywhere, and was not implemented the same way on all clones. So an earlier BIOS from a vendor might fall on its face because the vendor had not tested that software yet.

    Some clone BIOSes were really bad too. I sometimes swap out unknown BIOSes with a generic Phoenix BIOS.

  3. #3

    Default

    Is it in turbo mode mine would play intro then crash when it went to play the game
    turned off turbo game worked fine..
    Last edited by ChrisUnionNJ; September 18th, 2019 at 01:29 PM.
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  4. #4

    Default

    Quote Originally Posted by SomeGuy View Post
    Are the motherboards really identical? The first thing that comes to mind when I see a program that fails on an otherwise working motherboard is the BIOS. A different BIOS revision could easily cause problems like this.

    A particular author or company could try to use a BIOS call in some way that happens to work on a genuine IBM, but wasn't clearly documented anywhere, and was not implemented the same way on all clones. So an earlier BIOS from a vendor might fall on its face because the vendor had not tested that software yet.

    Some clone BIOSes were really bad too. I sometimes swap out unknown BIOSes with a generic Phoenix BIOS.
    I swapped the BIOS'es between the two machines and WhAm-BaM! "Bob's your Uncle!" they suddenly reversed roles! I dumped both chips and did a compare they are ever so slightly different but of course the boot screen says they are the same version!! LOL!!
    So I reprogrammed the one that was acting up and now... No More Problems!!!
    Thanks! As I probably would have started swapping RAM first had I not seen your post

  5. #5

    Default

    I had checked turbo mode. It ended up being BIOS!

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