[rescue] VAX 11/750s - Re: Linux wet paint, was Re: Spark10 CPU question (must fix - SPARC damnit :-) )

[Josh Dersch]

On 12/19/16 5:13 PM, John Hudak wrote:

>> I find myself greatly amused at the idea of a VAX 11/750 booting from a
>> "modern" computer whose sole purpose is to emulate a tape drive.
> Been doing that for years - booting my various VAXes and PDPs.  emulates a
> TU58.  Eventhough I have 3 working
> jTU58s, my lil windoz machine performs that job very well.
> And, if I need to speed things up, I run SIMH  (with RT, RSX, VMS) from my
> RL02 images on my i7-4xxx. (When I get some time, I have unix v6 (from a
> real Bell Labs tape and V7BDS which I need to cobble together.)
>
> My lab used to have 4-5 VAX750s. Never had any issues with PS.  the 11/34s
> were rock solid.  The only DEC gear that didn't compare was 11/44....seemed
> to suffer a host of ailments - ,mostly memory boards dropping bits...IIRC,
> the flaky ones seemed to have NatSemi memory.  Oh the fun times....My
> colleague across the hall used to take great pride in diagnosing the DEC
> machines before field circus showed up. - often made me wonder why we even
> had the svc agreement....but I digress...
> J
Anecdotes being data and all that, the 11/750 I have needed a lot of 
power supply work.  Off the top of my head there were two big ol' 
transistors, a diode, and a fusible resistor that needed to be tracked 
down and replaced.  That was in addition to replacing a fair number of 
large capacitors that were leaking goo.  I'm not all that great at 
diagnosing switching supplies, but I learned a little bit more getting 
this one going again.

(Incidentally, it's now heating my basement and will be until the fan 
noise starts annoying me again, if anyone wants an account, let me know...)

And anecdotally, the National Semiconductor memory boards in mine have 
been rock solid (knock on wood), and I had to swap out one DEC one :).  
But then, I've only been running it for a few days at a time here and 
there.  The NatSemi boards have the advantage of having all the RAM 
chips in sockets for easy repair, the manual even gives a guide for 
tracking down bad chips based on the DEC diagnostic.

Now I just need to fix the 4.3BSD-Quasijarus bootstrap to work properly 
with the CMD SCSI controller I have.  (Anyone out there an expert on 
MSCP?)  I like VMS well enough, but...

- Josh