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Thread: PS/2 Model 25-XT Optional Memory Modules.

  1. #31

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    Quote Originally Posted by bladamson View Post
    No 386es though? :< Will the 286 boards drop into the Model 25-XT without having to modify anything? What's the clock speed on that 286?

    Now, this is where it gets fun. The Model 25-286 runs at 10mhz. It's not a drop in replacement -- the XT system board only has the single power header, the -286 has the double header like the Model 30-286 and AT boards. You're going to have to get power to the other section somehow, perhaps tapping the existing lines somehow. Not sure how advisable it is, but it's been on my list of things to do.

    Unlike the XT board, the audio output jack on the -286 was built onto a module that connected to the system board via a cable. More than likely can be omitted, since it's really a useless connection, and a proper sound card would serve you much better.

    The only other thing I've wondered about is how the built in display will handle the VGA on the system board -- the XT has MCGA. The attachment is the same, via the pin header, but YMMV.

  2. #32
    Join Date
    May 2007
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    Quote Originally Posted by chulofiasco View Post
    Now, this is where it gets fun. The Model 25-286 runs at 10mhz. It's not a drop in replacement -- the XT system board only has the single power header, the -286 has the double header like the Model 30-286 and AT boards. You're going to have to get power to the other section somehow, perhaps tapping the existing lines somehow. Not sure how advisable it is, but it's been on my list of things to do.

    Unlike the XT board, the audio output jack on the -286 was built onto a module that connected to the system board via a cable. More than likely can be omitted, since it's really a useless connection, and a proper sound card would serve you much better.

    The only other thing I've wondered about is how the built in display will handle the VGA on the system board -- the XT has MCGA. The attachment is the same, via the pin header, but YMMV.
    I've VGA modded my 25-XT, even made a YouTube video on the subject. All good, it's just an analog CRT, but EGA 350 line mode will not work as it only monitors the vertical sync polarity for mode identification. It won't actually harm it but it will have no horizontal sync.

    https://www.youtube.com/watch?v=KjnbSpuq90I

    So just be aware of the 350 line EGA limitation and all is good.
    IBM PS/2 Model 25, NEC V30 8MHz, 640KB RAM, ATI VGA Wonder XL, 2GB SSD, Ethernet, DR DOS 6/GeOS, Xircom PE3 Ethernet

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