First boot on PDP-11/23! - VMS

This is a discussion on First boot on PDP-11/23! - VMS ; Powered 'er up and got "28/START?"!!! Yay, I made it to the console debugger! Help: The "28" means 28K detected. I have 256K installed. I have a memory problem. How can I proceed? The rest of this post is just ...

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  1. First boot on PDP-11/23!

    Powered 'er up and got "28/START?"!!!
    Yay, I made it to the console debugger!

    Help: The "28" means 28K detected. I have 256K installed. I have a memory
    problem. How can I proceed?

    The rest of this post is just a status report. Ignorable.

    ====

    Front pannel switches are labeled as follows (what do they do):
    RESTART HALT AUX ON/OFF
    LEDs are labeled:
    PWR OK RUN

    I left the switches on the back of the BDV11 enabled and didn't mess with
    them.

    If I RESTART in RUN mode, I get a "28/START?" prompt.

    I answer "N" to the "START" prompt. I get "173642/@". Book says that means
    "In console terminal test, a 'no' typed", so that's fine. Light D3 on the
    back of the BDV11 is on, meaning "Waiting for response from operator", so
    that's good too.

    The AUX ON/OFF switch seems to have no effect.

    I took a suggestion from Rob Brown and loaded 10000 with 014747
    (MOV -(R7),-(R7), a neat instruction) and started executing in HALT mode.
    Seems to work. Once I figure out how to output characters, I can hand
    assemble a "Hello world!" program.

    Everything seems good except the memory size. Can someone help me on that?

    ..wk.

  2. Re: First boot on PDP-11/23!

    In article ,
    William Korvine writes:
    > Powered 'er up and got "28/START?"!!!
    > Yay, I made it to the console debugger!
    >
    > Help: The "28" means 28K detected. I have 256K installed. I have a memory
    > problem. How can I proceed?


    I think 28KW is all the startup ever detects.

    bill

    --
    Bill Gunshannon | de-moc-ra-cy (di mok' ra see) n. Three wolves
    bill@cs.scranton.edu | and a sheep voting on what's for dinner.
    University of Scranton |
    Scranton, Pennsylvania | #include

  3. Re: First boot on PDP-11/23!

    bill@cs.uofs.edu (Bill Gunshannon) wrote in
    news:3dbu28F6sp4bsU1@individual.net:

    > In article ,
    > William Korvine writes:
    >> Powered 'er up and got "28/START?"!!!
    >> Yay, I made it to the console debugger!
    >>
    >> Help: The "28" means 28K detected. I have 256K installed. I have a
    >> memory problem. How can I proceed?

    >
    > I think 28KW is all the startup ever detects.
    >
    > bill
    >


    That would be nice. I think I'll poke (and peek) around and see if my
    memory actually exists.

    ..wk.

  4. Re: First boot on PDP-11/23!

    bill@cs.uofs.edu (Bill Gunshannon) wrote in
    news:3dbu28F6sp4bsU1@individual.net:

    > In article ,
    > William Korvine writes:
    >> Powered 'er up and got "28/START?"!!!
    >> Yay, I made it to the console debugger!
    >>
    >> Help: The "28" means 28K detected. I have 256K installed. I have a
    >> memory problem. How can I proceed?

    >
    > I think 28KW is all the startup ever detects.
    >
    > bill
    >


    Ok, I used ODT and poked values into n00004 where 0<=n<=7 and read the
    correct values back. I conclude that despite the value at the START prompt,
    I actually have 256K of working RAM.

    I'm going to end my works here for a little while. For those who have been
    following my travails, thanks for your attention and aid.

    I now have a working CPU with 256kb of RAM and a working 4-port serial
    card. This is everything I planned to accomplish at this stage.

    I have no storage devices, so there's not much more I can do until I get
    them. Since I have no room for RL or RX drives, I must wait for a SCSI
    interface to become available or build an emulator device. I've seen the
    plans for the emulator boards such as at
    http://www.geocities.com/saipan59/dec/rxv11_emu.html
    and doubt I will attempt it. Besides, if I wanted an emulated PDP, I would
    have downloaded one.

    I still have the RLV11 boards, although the capacitors on one of them are
    physically damaged and need replacing. I will probably attempt that
    eventually just to preserve the boards. And who knows, I might have room
    for RLs some day.

    Last post for a little while. Thanks, and take care.

    ..wk.

  5. Re: First boot on PDP-11/23!

    William Korvine wrote:

    > bill@cs.uofs.edu (Bill Gunshannon) wrote in
    > news:3dbu28F6sp4bsU1@individual.net:
    >
    > > In article ,
    > > William Korvine writes:
    > >> Powered 'er up and got "28/START?"!!!
    > >> Yay, I made it to the console debugger!
    > >>
    > >> Help: The "28" means 28K detected. I have 256K installed. I have a
    > >> memory problem. How can I proceed?

    > >
    > > I think 28KW is all the startup ever detects.
    > >
    > > bill
    > >

    >
    > Ok, I used ODT and poked values into n00004 where 0<=n<=7 and read
    > the correct values back. I conclude that despite the value at the
    > START prompt, I actually have 256K of working RAM.
    >
    > I'm going to end my works here for a little while. For those who have
    > been following my travails, thanks for your attention and aid.
    >
    > I now have a working CPU with 256kb of RAM and a working 4-port
    > serial card. This is everything I planned to accomplish at this stage.
    >
    > I have no storage devices, so there's not much more I can do until I
    > get them. Since I have no room for RL or RX drives, I must wait for a
    > SCSI interface to become available or build an emulator device. I've
    > seen the plans for the emulator boards such as at
    > http://www.geocities.com/saipan59/dec/rxv11_emu.html
    > and doubt I will attempt it. Besides, if I wanted an emulated PDP, I
    > would have downloaded one.
    >
    > I still have the RLV11 boards, although the capacitors on one of them
    > are physically damaged and need replacing. I will probably attempt
    > that eventually just to preserve the boards. And who knows, I might
    > have room for RLs some day.
    >
    > Last post for a little while. Thanks, and take care.
    >
    > .wk.


    What you will find is that the PDP-11's basically use 28K for memory
    and 4K to address what they call the I/O page. Unlike the Intel type
    processor that has an input and output instruction the PDP's (and
    VAX's) used memory mapped I/O. Also to use memory greater than 28K it
    is done with memory management hardware that rearranges 4k pages to
    point to different areas of physical memory. The PDP-11/23 also has a
    memory management seperation for kernel and user mode operation. This
    allowed some added protection, such as a user mode "HALT" instruction
    would not execute instead it would cause an illegal instruction TRAP to
    occur.
    The VAX was similar but with it's 32 bit data paths it could address
    more memory pages at a time and it had supervisory memory management
    mode.

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