DEC M9312 Configs for a 11/40

Josh Dersch derschjo at
Mon Nov 28 10:33:55 CST 2016

On 11/28/16 7:11 AM, william degnan wrote:
>> If you really want to make a bootable XXDP TU58 tape image, the
>> instructions given by AK6DN here:
>> a-bootable-XXDP-file-for-TU58-emulator
> this is what I have been doing.

And what does the TU58 bootstrap do when you attempt to boot?  Do you 
see any activity over the second SLU talking to the emulator?
> <snip>
>>> I use both the M9312 DL ROM and manually entering in the bootstrap without
>>> the M9312 installed (replace with terminator card).   With the ROM method
>>> the system repeats an attempt over and over.
>>> system is looping between instructions 173022 -->173156 (error reset the
>>> world), 173160 (retry)..back to 173022
>>> When I first power on the values in the control status register (774400)
>>> are good. 1-6 and 8-13 are cleared, bit 7 is set.
>>> After I attempt to boot (DL at the @ prompt), you can see the light
>>> pattern
>>> repeat over and over, looping through 173022 -->173160.
>>> I HALT the system and recheck the control status register. This time
>>> 15 - error (composite error (ERR))
>>> 10 - EO (operation incomplete (OPI))
>>> 7 - stays lit
>>> function code F2 = 1, F1 =1, F0 =0. this code indicates "HFT" (Header Not
>>> Found)
>>> To me (and this is just me) the bootstrap is not waking up the RL11
>>> controller, and can go no further.
>> According to the user's guide: http://bitsavers.trailing-edge
>> .com/pdf/dec/disc/rl01_rl02/EK-RL012-UG-004_RL01_RL02_
>> Disk_Subsystem_Users_Guide_Oct80.pdf
>> If the CSR bits are as you report, the drive got the Read command (that's
>> what F0-F2 indicate -- the last selected function, in this case "Read
>> Data").  Bit 15 indicates a composite error, and bit 10 indicates OPI, as
>> you note.  I don't see anything in there about HFT unless you left out some
>> bits.
>> If indeed bit 12 is set (indicating HFT) then the "Header Not Found"
>> indicates that the drive was unable to find the header for the sector on
>> the disk, which makes it look like the drive is trying to read but for
>> whatever reason isn't able to find the sector.  This could be a damaged
>> disk, misaligned heads, or any number of logic failures.
>> I would start with the RL02/RL11 diagnostics via either XXDP or PDP11GUI
>> and go from there.
> this just bombs, does not run.  I agree though.  basically the computer
> says "I can't reach the controller"
No it doesn't say that.  As indicated by the fact that you can see the 
controller's CSR register from the front panel and the console PROM 
monitor, and that the bootstrap is able to write to it during 
execution.  The controller is responding, and it's saying "sorry, I was 
unable to read anything."  If the controller wasn't responding, the CPU 
would trap on execution (a Bus Error Trap, to location 4).

> I should add that the RL ROM (run DL0
> from CONSOLE prompt) keeps trying over and over again, you can see it.  If
> you run the bootstrap from the front panel it just dies.
Yes, this is expected.  If you look at the listing here: 
you can see that what happens on an error after a Read Data command is 
that the bootstrap does a RESET and jumps back to the beginning to 
retry, indefinitely.  (See line 91).  There is likely a problem with 
your drive, the controller, the disk, or the cabling, or some 
combination of these things.

> What I can do next is make more note of the registers, see if I can get
> more clues.
Yes, that might  be a good idea.  Single-stepping through the bootstrap 
(with the aforementioned listing at your side) might be revealing.  I 
assume you've run all the 11/40 CPU diagnostics and exercisers?

> It just seems to me that there is a CPU or UNIBUS issue when I see
> performance like this, again my hunch. It's not the controller.  If the
> disk was bad, it'd at least try something, you'd see something.
You are seeing something, in the controller's CSR register.  What is it 
you're expecting to see?

- Josh

> b

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