help needed: problem with UNIBUS access on my PDP-11/70

From: Tom Uban <>
Date: Thu Jul 11 07:49:01 2002

Hi Henk,

Have you tried to read the DL11-W status register? Do you only get
the PAUSE on a deposit?

As you indicate, checking the power supply voltages is an important
first step.

It sounds like you might have a bus request/grant jumper problem or
problem in the CPU hardware. Since you are using slot 40 (the first
UNIBUS slot) for your DL11-W, it would seem that the problem would
be either in the MASSBUS jumpers or a CPU hardware problem. Of
course, it could also be a backplane wire problem.

Have you tried to execute a very simple program such as jump to
self (0777) by depositing that value at location 01000 and starting
there? This is a good basic CPU test.

Do you have a KM11 diagnostic board? Using the KM11, you can
cycle through the microcode flows listed in the printset. This will
help you diagnose the problem at a finer level then just watching
the pause lamp turn on. Of course, you will likely need a set of
board extenders and minimally an o-scope as well. If you don't
have a KM11 and want to build one, check out the one I built here:


At 09:31 AM 7/11/2002 +0200, you wrote:
>Hi all.
>I am having trouble with my 11/70 because it works only partial.
>Since things are quiet on the list, I have something to ask.
>It is a long story, but as said on the list this week, the more
>info you give, the less not relevant suggestions are typed.
>First the description of the machine.
>The machine has only all CPU boards (with FP), the DL11-W and
>3 MASSBUSS interfaces. The fourth MASSBUS interface has in the
>correct slot a G727. All other UNIBUS slots have a G727 in the
>card position D. The MOS memory box is also connected to the CPU.
>This is what I have done so far.
>When I turn on the machine everything "looks" fine. With the switch
>ENABLE/HALT on HALT and pressing START, the machine sort of resets.
>With the panel I can dump data in the MOS memory at address 00000000.
>I did this also at 00001000 and 00010000. It 'works' and when I read
>the contents back from those addresses, it is the correct data.
>So, my first conclusion is that (part of) the CPU is OK and that the
>address and data path to the MOS memory and the MOS memory box itself
>are all OK as well.
>Here is the part that worries me.
>In slot #40 (IIRC) is the DL11-W (M7856) console interface.
>I am trying to write to the transmit buffer address (XBUF - 17777566).
>I set the knobs on the 11/70 console to "CONS PHY" and "DATA REGISTER"
>so that the address on the switches is the real physical address and
>the data on the switches is what I want to store.
>After the reset of the machine (HALT/START) I set the switches to
>17777566, and press LOAD ADRS. On the ADDRESS leds appears 17777566.
>Now, I set the switches to 00000071 (should give a "9" on the VT220).
>When I toggle the DEP button, the PAUSE led goes on.
>According to the handbook that means the the CPU tries to finish the
>instruction as far as possible and then waits for an event to finish.
>The event could be (I assume) an interrupt or, in this case, access
>to the UNIBUS section.
>Next test was checking the DL11-W interface.
>First I switched on my 11/34C. With address 165020/START, I get the
>dump of the registers on the VT102. So, I mad sure that the M7856
>in the 11/34C is OK.
>Now, I swapped the M7856 of the 11/70 with the M7856 of the 11/34C.
>First, I started the 11/34C again. I get the register dump on the
>screen. So, the M7856 from the 11/70 was OK.
>Just to make sure I tried the 11/70 again (with M7856 of the 34C),
>but I get the same result: PAUSE led goes on.
>Yesterday, I had a long conversation on the phone with Edward. We
>talk about all kind of (PDP-11) things, and also the 11/70 problem.
>One suggestion was that the UNIBUS map is not yet initialised, and
>that would cause the UNIBUS accesses to fail. My guess is that when
>the console panel knob is set to "CONS PHY", I have full access to
>all addresses without any mapping taking place. Is this correct?
>Anyway, to test the "UNIBUS map initialisation" theory, I read the
>M9312 bootstrap manual. The 11/70 (and 11/60) have a different PROM
>that stores the diagnostics. The 11/04--11/55 PROM also contains a
>console monitor, but the 60 and 70 PROM only has diagnostics.
>The manuals says to load address 17765744, then set the switches
>8-0 to the device code and then press START.
>I checked the M9312 to look at the diag PROM. According the M9312
>manual the PROM code must be 248F1 (IIRC) for the 11/04-11/55, and
>233F1 for the 11/60-11/70. My M9312 has a PROM with code 616F1.
>Is that a new type for the 11/70? The M9312 is the card that was
>in the 11/70 when I got it, and another 11/70 (with remote console)
>that I have has the same PROM. Edward's 11/70's (he has also 2)
>one has a 233F1, the other has a 616F1.
>So, I did that test, but the PAUSE led goes on again.
>Trying to boot from an RX01 should need at least the RX11 card in
>a UNIBUS slot ... I did that, so I put the M7846 in slot 41 (IIRC),
>next to the DL11-W. Tried the test again: 17765744 - LOAD ADRS - set
>the device code on switches 8 to 0 - START. Alas, PAUSE on again.
>What puzzles me is the "device code" you must set on the 9 least
>significant switches. I have set that to 170 as that are the LSB's
>of the start address fro the bootstrap of the RX11. Is that correct?
>Come to think of the good advice from Tony: I will check the
>power supply voltages this evening. Especially the one that supplies
>the cards that deal with the UNIBUS section ...
>tnx for reading all this,
>and TIA for all responses,
>- Henk.
Received on Thu Jul 11 2002 - 07:49:01 BST

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