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Thread: OS8 Disk Server Console TTY Baud Rate

  1. #21

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    Quote Originally Posted by NicolasF View Post
    I noticed that the first EMA light turns on and I checked this video:

    https://www.youtube.com/watch?v=9qHrEkjavUc

    And the light never turns on, I have no idea how to find the problem, any ideas?

    How many Banks of RAM do you have? You will need at least 8k of RAM. That means bank 0 + 1. Can you switch between these banks?

  2. #22

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    Quote Originally Posted by gnupublic View Post
    How many Banks of RAM do you have? You will need at least 8k of RAM. That means bank 0 + 1. Can you switch between these banks?
    I have 2 banks 0 and 1. I can switch between them using the LOAD EXTN ADDR key.

  3. #23
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    Quote Originally Posted by NicolasF View Post
    I have 2 banks 0 and 1. I can switch between them using the LOAD EXTN ADDR key.
    With 8KW you should be able to run:

    1) memory extension control test MAINDEC-08-DHMCA-A: https://www.ak6dn.com/PDP-8/MAINDEC/...ory_extension/

    2) extended memory data and checkerboard test MAINDEC-08-DHKMA-A: https://www.ak6dn.com/PDP-8/MAINDEC/MM8-EJ_memory/

    The first will test the EMA logic works as expected, second is a data test that will check all 8KW of memory, using relocation as necessary.

    I use these on my 16KW 8m all the time to check it.

    Don

  4. #24
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    Quote Originally Posted by NicolasF View Post
    There is one step from the how-to.md guide that I did not do, and that is "### INSTALLING THE SYSTEM HANDLER ###" (no idea what system handler is and what it does).
    I assumed that thing is already installed in the diagpack2.rk05 provided in the zip os8diskserver file that you download from the github project. Could this be the problem?
    Is there anyway I can check if that thing is installed in the image?

    Thanks!
    What you are seeing is exactly what I would expect if you did not install the system handler on your boot image.

    The system handler is the part of OS/8 that knows to talk to the serial disk server when it reads or writes to the SYS device. A normal RK05 image wants to talk to the RK05 hardware when OS/8 wants to talk to the SYS device.

    What is happening is the Serial disk boot 1 code which you toggled in or is on some boot card sends a wakeup character to the serial disk server. I believe there is a special wakeup for booting which makes the boot sequence shorter. The boot code on the 8 then starts waiting for the server to send it 256 words which are usually written on field 0 at memory location 0. The 256 words sent are the first 256 words on the disk image. The boot program will get overwritten in a controlled manner after about 20 - 30 words and the boot loader that was on the boot image takes over at that point. If the initial boot does not match the boot on block 0 on the drive then the boot will fail. There is no handshaking between the serial disk boot and the serial disk server. The server sees the wakeup and sends all 256 words in the blind and then reports that it is done. There are three pieces of code in that 256 words. The first piece is what I call boot2 and it is the code that takes over at some point in the boot process. The second piece is the field 1 resident code for OS/8 and the third piece is the OS/8 resident code that goes in the last page of field 0. It is this piece that has the OS/8 entry point at 7500 and 7605 and the SYS device handler.

    Is there anyway to tell if it is installed? The easy way is to try to boot it as an RK05 image under simh. If it boots then it is not installed.

    Follow the instructions and install the system handler on your boot image and try again.

    Best Wishes!
    Doug

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