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Thread: Cannot access multiple MSCP (DUx:) drives under SIMH RT11

  1. #1

    Default Cannot access multiple MSCP (DUx:) drives under SIMH RT11

    I have the following ini file for my simulated PDP11

    echo PDP-11/93 with 4M of memory
    echo
    set cpu 11/93, 4M

    ;SET RL ENABLE
    ;SET RL0 RL02
    ;SET RL1 RL02
    ;SET RL2 RL02
    ;SET RL3 RL02

    ;ATT RL0 DISK0.DSK
    ;ATT RL1 DISK1.DSK
    ;ATT RL2 DISK2.DSK
    ;ATT RL3 DISK3.DSK



    SET RQ ENABLE
    SET RQ0 RD54
    SET RQ1 RD54
    ATT RQ0 DISK0.DSK
    ATT RQ1 DISK1.DSK


    SET TS ENABLE
    ;SET TS0 FORMAT=TPC
    SET TS0 LOCKED



    SET DZ ENABLE
    SET DZ LINES=8
    ;ATTACH -am DZ 11023

    SET LPT ENABLE
    ATTACH LPT PRINTER.TXT

    BOOT RQ0

    Machine boots fine and I can do a DIR, DIR DU0: and get a directory fine.
    Doing a DIR DU1: results in an error.
    If I uncomment the RL02 drives I am able to do a directory on DL1: which is the same image attached to DU1.

    Any thoughts?

    Thanks.

  2. #2
    Join Date
    Nov 2014
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    The mapping for the RT11 Volumes for a MSCP device are stored in the device handler as partitions of a single disk drive. After booting do the following to show the mapping of unit to controller, unit and partition. It should look like the following:

    .sh dev:du



    Device Status CSR Vector(s)
    ------ ------ --- ---------
    DU Resident 172150 154


    DU0: is set PORT = 0, UNIT = 0, PART = 0
    DU1: is set PORT = 0, UNIT = 1, PART = 0


    To change the mapping….

    .set du1 port=0,unit=1,part=0 ! for DISK1.DSK

    Then reboot. Note that a RD54 sized disk could also support many RT11 sized partitions on a single disk.

    Jerry

  3. #3

    Default

    Jerry,

    Thanks so much. That did the trick!

    Brian.

  4. #4

    Default

    One other quick question. If I want to enable RQB, do I have to do a sysgen? I remember that RT11 only supports one MSCP controller by default. And when it is enabled, what would the device names be called.

  5. #5
    Join Date
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    Chicagoland
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    Default

    I don't have any experience with this one. I think the Port=x will address a different controller up to 4 (total) in the same handler. You can set the addresses with SET DU CSRx=nnnnnnn or SET DU VECx=nnn.

    See http://bitsavers.trailing-edge.com/p...nual_Aug91.pdf (section 2-19) or
    http://www.bitsavers.org/pdf/dec/pdp11/rt11/v5.1_Jul84/AA-M240B-TC_RT-11_System_Generation_Guide_Jul84.pdf


  6. #6

    Default

    Every partition will be exactly 65536 blocks (32MB), except that the last partition on the drive will take up whatever space remains and will therefore be 65536 blocks or less in length.
    There’s no way to setup shorter partitions. For example, you cannot partition a 44MB drive into 4 x 11MB drives.
    When you do a low-level format of a physical drive, that formats the entire disk surface. So after you setup drive partitions, you will not need to do another low-level format. All you need to do is INIT the new partitions that you have not previously used, to write a directory structure to them.

    https://www.besanttechnologies.com/t...ute-in-chennai

  7. #7
    Join Date
    Nov 2014
    Location
    Chicagoland
    Posts
    177

    Default

    Quote Originally Posted by vimalasasi View Post
    Every partition will be exactly 65536 blocks (32MB), except that the last partition on the drive will take up whatever space remains and will therefore be 65536 blocks or less in length.
    There’s no way to setup shorter partitions. For example, you cannot partition a 44MB drive into 4 x 11MB drives.
    When you do a low-level format of a physical drive, that formats the entire disk surface. So after you setup drive partitions, you will not need to do another low-level format. All you need to do is INIT the new partitions that you have not previously used, to write a directory structure to them.

    https://www.besanttechnologies.com/t...ute-in-chennai

    Charlie Wilson released a set of handlers called DUCM (release 5d) in 1992 that allows you to create custom sized partitions. You have to compile the handler to enable the feature.

    From the released notes -

    (6) DUCM optionally allows splitting of discs into logical units of smaller
    size than 65535 blocks. (V5c)


    Jerry

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