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Thread: KL8e (M8650D) question

  1. #1
    Join Date
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    Default KL8e (M8650D) question

    I have a PDP8/m with an 8650D serial card. The card is fitted with a 14.418 MHz crystal, and jumpered for 110 baud. From Doug Jones' page seems to imply that with this crystal, only the 110 baud rate is supported, but the M8650YA version with the 19.6608 MHz crystal supports multiples of 300 baud. Is that correct? Is the xtal frequency the only difference between the two versions?

    If I replace the crystal with a 19.6608 MHz crystal, can I go ahead and jumper for, e.g., 9600 baud?

    Thanks in advance!!

    Dave

  2. #2
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    Yes - Doug's pages are a great resource for these boards (M8650 and M8655). I've had complete success with the M8650 crystal upgrades and his various higher speed configurations (up to 38400) for at least a half-dozen of these boards.

  3. #3

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    There is also a capacitor that you need to change (or remove). Also described on Doug's excellent page.

    Also check if the J jumper (soldered) is set for two stopbits, 2-3 connected. You probably what to move this to 1-2 to get one stop bit.

    It is also possible to get 115200 baud on this board which makes sense if you wan't to use it with serialdisk. Then you need a 14,7456MHz crystal and one small modification. I've did that, and I have posted a description of it on another forum, written in Swedish. I can do a translation if someone is interested.

  4. #4

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    Quote Originally Posted by anders_bzn View Post
    It is also possible to get 115200 baud on this board which makes sense if you wan't to use it with serialdisk. Then you need a 14,7456MHz crystal and one small modification. I've did that, and I have posted a description of it on another forum, written in Swedish. I can do a translation if someone is interested.
    Oh nice! I guess that is selecting the 153600 baud wire and changing the xtal to 14,7456MHz only?
    http://homepage.divms.uiowa.edu/~jon...rd8e/kl8e.html
    153600 Baud / 19.6608MHz * 14,7456MHz gives 115200 Baud then...
    Or are there any other modifications needed as well?

    Is this speed stable? Or are we stressing some components here?

    Regards, Roland
    WTB: Dec TU56 / Case for Altair 8800 ...... Rolands Github projects

  5. #5

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    Yes you are right, the only thing I had to do was remove the capacitor, strap it for 153600 and change the crystal.

    Then I changed number of stop bits 2->1 and device address to 40/41. I use this with serial disk and I have no problems with it. However I read somewhere that 2 stop bits on the server side where recommended. I use this setting.

  6. #6

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    I actually did a write up on this: https://www.pdp-9.net/configure-m865...for-serialdisk

  7. #7
    Join Date
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    With all this interesting stuff going on with the pdp8/e/m, especially Rolands work! I am keen to make more use of the 8/m I have, which is near to functioning, but I will be needing a M8650 board,for console I/O. this would enable me to make some more progress, If anyone has a spare M8650 board, or can put me in touch with one for sale, that would be great news. Sorry for jumping in ! I noticed the heading which prompt me for one of these.

    thanks

    Harry

  8. #8
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    I can probably help you out - PM me if you're interested. I'm on the wrong side of the ocean from you, of course.

  9. #9
    Join Date
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    Jack,
    Thanks for your quick reply! PM sent

    .....Harry

  10. #10
    Join Date
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    Thanks for the great write-up and photos in your link. I followed your directions closely [and carefully] and have my M8650 up and running in my PDP8/E at 115200 baud.

    SerialDisk is certainly running fast now vs my previous setting at 9600 baud.. Has not crashed [yet].

    Regards, Matt

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