Re: 11/40 misbehaviour

From: RHB (dcs8506_at_bellsouth.net)
Date: 08/11/04

  • Next message: Rich Alderson: "Re: 11/40 misbehaviour" 
    Date: 11 Aug 2004 12:39:04 -0700

    Rich Alderson <news@alderson.users.panix.com> wrote in message news:<mddhdramrlu.fsf@panix5.panix.com>...
    > John Santos <JOHN@egh.com> writes:
    >
    > > Are you sure it is a PSW bit 4 (T bit, indicates trace trap), and not a
    > > trap through the vector at 4? <snip>
    >
    > Yes, I was quite sure. I was, however, confusing two occurrences. Error code
    > TBT is "T-bit trap"--and I did get it on the other box, quite often.
    >
    > > Trap through 4 could be anything... T4 is Timeout and other errors,
    > > according to my PDP 11/40 Processor Handbook. A Unibus timeout could
    > > be caused by incorrect device configuration, but I think the device
    > > setup code at boot time should try to protect you against this. (It
    > > does on RSTS, by disabling non-existent devices, but I'm not nearly
    > > as familiar with RSX.) Memory could be going out to lunch, and failing
    > > to respond to reads or writes. Or the bus cable(s), jumper(s) or
    > > terminators could be bad, and randomly changing an address bit causing
    > > a memory or device address to be wrong.
    >
    > Error code T04 is precisely this, bus timeouts or odd-address word references.
    >
    > > Have you tried all the standard things, i.e. reseating boards, checking
    > > PS voltages, etc.?
    >
    > Yes.
    >
    > > If that doesn't help, try paring down the system to the minimal
    > > working configuration (CPU, console terminal, enough memory to run,
    > > and the system disk) and then add things back one at a time until
    > > the problem recurs.
    >
    > This is a minimal system: 28KW memory, console, RH11, RX01.
    >
    > > I haven't seen PDP-11/40 diags in years. We used to have a tape
    > > (9-track, 800 bpi) of them, but it is long gone.
    >
    > Just on general principles, and not my own need, that's too bad.

    Do you have a scope to look at levels on the unibus ?

    Does the system run but die intermittently or is it flat out dead ?

  • Next message: Rich Alderson: "Re: 11/40 misbehaviour"

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