Re: need a bit of early boot help

Den 2025-11-28 kl. 01:49, skrev Dave McGuire:
> On 11/27/25 12:05, Anders Magnusson wrote:
>>>    Summary: IT RUNS!
>>>
>>>     The problem was in the CIB board, a failed 74S74 flip flop in 
>>> interrupt handling.
>>>
>>>    We'll post pics and such soon.
>>>
>>>    Thanks everyone for the guidance.  We'll try booting VMS on it 
>>> later tonight, temporarily from the VAX-11/750's system disk.  If 
>>> all goes well there, we'll set up permanent system disks for it for 
>>> VMS, NetBSD, and possibly Ultrix-32.
>>>
>>>    Incidentally, this is the same '780 that Gunther Schadow had 
>>> quite a saga with on this very mailing list, back in 2002.  To my 
>>> knowledge he never did get it running.  We fixed a number of 
>>> hardware problems in this machine, so it's no wonder he'd had such a 
>>> tough time with it.  It was many months of work, off and on, over 
>>> several years for us here at LSSM.
>> Cool! Real hardware fix!
>>
>> How did you manage to find the failing chip?  I.e. the error 
>> isolation process? :-)
>
>   Well, the big break was information on this list, that the first 
> character of the line where it stalled was the first thing printed 
> with interrupts.  That quickly led us to the console TX interrupt flip 
> flop on the CIB board.  Three of us looked at the schematics that 
> night, separately at home, and all reached the same conclusion.
>
>   Booting VMS on the machine told us nothing, but the NetBSD kernel is 
> far more verbose.
>
>   The microdiagnostics specifically flagged the M8230 (CEH) as being 
> bad, but it was the CIB.  Now the M8230 tests pass too.
Good work!

...if it had been 45 years ago you could have bug-reported the 
diagnostics to DEC for pointing out the wrong hardware :-)

-- R