Talking to a VAX4000/300; Also RAM

[Dave McGuire]

On Nov 3, 2009, at 9:38 AM, JP Hindin wrote:
>>> What line speed are you running at?  I have a 4000/300, too (great
>>> machine - congratulations!), and I haven't had that problem with
>>> either a VT420 or a terminal emulator.  I'm using 8N1, so I'm sure
>>> you're right there.  But I wonder if the VT240 is just not keeping
>>> up with the VAX, i.e. insufficient speed and buffer space.  I've
>>> seen that before, where a terminal *can* talk 9600 but can't do it
>>> for very long.  Hm, I think I have a VT240, maybe I should give it
>>> a try....  -- Ian
>>
>>    VT240s, while wonderful in other ways, are very slow terminals.
>> It wouldn't surprise me if he were simply getting overruns.
>
> Much to my embarrassment I discovered the issue was _not_ the  
> speed, or
> noisy lines, or corroded batteries or RS232/423 problems. I was a  
> total
> nitwit and neglected to notice I had it set to 8E1 instead of 8N1.
> Remarkably with this small change, I can now speak to it clearly at
> 9600bps.
> <Hand to forehead repeatedly and with force>

   Ahem. ;)

> Should I be amazed or not that this 4000/300 has a half-gig of RAM? My
> first 4000/300 came with a single 32M board, this one comes with 4x  
> 128M
> boards (one of which is flaky). The documentation I can find says the
> 4000/300 maxes out at 128M, which... clearly isn't so:
> http://www.kiwigeek.com/misc/VAX4000_Mem_Count.JPG

   Holy crap!!  That's a huge amount of memory on a VAX.  HUGE.  Score!

> Where would the sages suggest I begin in tracking down a fault in  
> one of
> the four boards:
> http://www.kiwigeek.com/misc/VAX4000_Mem_Errors.JPG

   Hmm, ouch. :-(  Is the service manual for the '300 CPU around?  It  
should tell you how to decode the message and will probably get you  
down to the chip level.

            -Dave

-- 
Dave McGuire
Port Charlotte, FL