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Thread: PDP-9 at the RICM

  1. #101

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    That's Superior for ya.
    Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73
    Synthesizers: Roland JX-10/SH-09/MT-32/D-50, Yamaha DX7-II/V50/TX7/TG33/FB-01, Korg MS-20 Mini/ARP Odyssey/DW-8000/X5DR, Ensoniq SQ-80, E-mu Proteus/2, Moog Satellite, Oberheim SEM
    "'Legacy code' often differs from its suggested alternative by actually working and scaling." - Bjarne Stroustrup

  2. #102
    Join Date
    Jul 2014
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    Rhode Island
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    We tried to format a DECtape on the PDP-9 using the paper tape that Mattis punched for us. The formatter program loads and runs, but doesn't like the zero that we entered for the drive number. We halted and singled stepped the formatter program, entered a zero, and found a 360 in the AC instead of a 060. We tried all of the possible combinations of data bite, parity, and stop bits with the same results. We tried Warren's 20mA-RS232 adapter with my laptop, and even a real ASR33, with the same results. So it looks like the serial console input shift register is broken.

    Even if we had gotten ADSS to boot this week we would not have been able to talk to it with a broken serial console. Oh well, this should be easy to debug and fix.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  3. #103
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    I am learning way more than I wanted about dumprest for the PDP-9. The dumptd8e_18 that is on that is on Dave's WWW page does not fiddle with the format of the DECtape image file that is saved on your PC. You need to post process the PDP-8 (16-bit Integers holding 12-bit words) into PDP-9 (32-bit Integers holding 18-bit Words) and convert groups of three 12-bit words into two 18-bit words. The crew at LCM wrote a tape image mangler program to do that.

    The version of dumptd8e_18 that Anders made has the PDP-9/PDP-8 mangler code built in, so it receives the PDP-8 serial data and then saves the DECtape image in PDP-9 format.

    I used the resttd8e_18.c from Dave's WWW site to make the ADSS DECtapes for the PDP-9. This version does not have the mangler code built in, so the DECtapes that I wrote contained garbage.

    I need to add reverse-mangler code to resttd8e_18.c so that it can read a PDP-9 formatted DECtape image, format the serial data stream into PDP-8 format, and then have the resttd8e_18.pal program write a PDP-9 DECtape.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  4. #104
    Join Date
    Sep 2019
    Location
    Zurich, CH
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    27

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    Have you considered looking at PIP10 in OS/8, which already exists, was designed for 18-bit DECtapes, and was extensively tested back in the day?
    Either make use of it directly, if the file systems are compatible, or use it as a source for your code. That's what I did when I needed to dump PDP-9 DECtapes a few years ago. Copied PDP10.PA, modified things around, and dumped blocks from DECtape.

  5. #105
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    Jul 2014
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    Rhode Island
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    Quote Originally Posted by bqt View Post
    Have you considered looking at PIP10 in OS/8, which already exists, was designed for 18-bit DECtapes, and was extensively tested back in the day?
    Either make use of it directly, if the file systems are compatible, or use it as a source for your code. That's what I did when I needed to dump PDP-9 DECtapes a few years ago. Copied PDP10.PA, modified things around, and dumped blocks from DECtape.
    BQT,

    I used PIP-10 to extract files from a PDP-10 KA10 DECtape a few weeks ago. I should look at the code.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  6. #106

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    Have you tried booting V0 Unix on it?

  7. #107
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    Jul 2014
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    Rhode Island
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    I got the PDP-9 to format DECtapes today. The clock that generates the timing track was running a little slow, so it ran off the end of the tape before it finished. It is currently adjusted to have a 32.2us bit time, instead of the desired 33.3us. This works when formatting a tape, and is well within the tolerances for DECtape.

    The next project is to write the code to send an 18-bit SIMH DECtape image, converted into 12-bit format, converted into bytes, sent out the serial port to a modified resttd83, and onto a real DECtape.

    We are getting really close to booting ADSS on the PDP-9.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  8. #108
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    Jul 2014
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    Rhode Island
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    I modified resttd8e to work with PDP-9 SIMH DECtape images and was able to make physical DECtapes.

    Today we got the PDP-9 to boot the ADSS V4E monitor from DECtape. There are still some issues with how ADSS is running, and it looks like ADSS found a problem with the Priority Interrupt System not being turned off by a console reset. Tomorrow we will try some other versions of ADSS to see how they run.

    RICM_PDP-9_ADSS.jpg
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  9. #109
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    Mar 2004
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    Wilmette, IL (north of Chicago)
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    Good stuff!

  10. #110
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    Jul 2014
    Location
    Rhode Island
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    We connected an ASR33 Teletype to the console port on the PDP-9 today. Much more fun than the VT220.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

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