[Info-vax] Some questions on software for VMS 7.3 VAX

[John E. Malmberg]

On 1/15/2016 5:00 AM, hb wrote:
> On 01/15/2016 10:31 AM, lists at openmailbox.org wrote:
>
>>> This is based on the emacs21_2.zip from the 8.0 freeware cd. There are a
>>> couple of changes to let emacs make a computer slow. It looks like that
>>> code was never built or tested on VAXes. Also, this VAX is a simh and I
>>> use the console, OPA0:, set to a reasonable baud rate. I can't get it to
>>> work when logged in via telnet to port 60123, which is a simh DZ device,
>>> aka TTA0:. The process hangs in LEF with two busy channels to TTA0:. I
>>> have/had other problems with that device: "-SYSTEM-W-DATAOVERUN, data
>>> overrun" when I type very fast, aka do a cut and paste. So, it's not yet
>>> production quality, but for hobbyists ...
>>
>> If it overruns it's not ready for hobbyists either. Very little is worse
>> than an editor that doesn't work or screws up your code.
>
> Maybe I didn't make it clear, to me this is a simh problem, not an Emacs
> problem. The overrun shows in DCL. I didn't try to debug the hang in Emacs.

It is entirely possible that the SYSTEM-W-DATAOVERUN can be reproduced 
with a physical VAX of the same speed or slower rating as the SimH system.

The DZ device family does not have buffering and will not work reliably 
for high speed input.

Using them for high-speed output is self-limiting.  They will chew up so 
much CPU that it will throttle the output, and anything else you are 
attempting to do.

It is also possible to bugcheck a physical VAX by sending data to 
multiple DZ interfaces too fast at the same time.  I have seen it happen 
multiple times.  The only fix is to change to using a better serial 
controller.

A DZ interface is basically good enough for human typing speed.  If you 
are trying anything faster over it, you are rolling the dice.

Which is why trying to use the serial console of a VAX for anything 
other than system maintenance very bad idea, since that is almost always 
a DZ port.

Regards,
-John
wb8tyw at qsl.network