Still pineing for my own VMS machine

From: Robert Schaefer <rschaefe_at_gcfn.org>
Date: Wed Jun 5 20:45:19 2002

----- Original Message -----
From: "Ethan Dicks" <erd_6502_at_yahoo.com>
To: <cctalk_at_classiccmp.org>
Sent: Wednesday, June 05, 2002 04:33 PM
Subject: RE: Still pineing for my own VMS machine


>
> DECnet is a byte-oriented protocol over an unspecified physical
> medium (typically RS-232 or V.35). What may be occurring here
> is that the modem _is_ a plain-old-dumb (sync?) modem, but the byte
> protocol between the VAX and the Customer Care center in Colorado
> (where Remote Diagnostics folks used to reside) is a DDCMP or simplified
> DDCMP connection as opposed to some other proprietary method of
> packaging the requests and data.
>

Well, it plugs directly into the console of the VAX, so if it does speak
something fancy, it's a good bet the processing is done in the
modem-thingie. I guess I *could* plug a vt220 into it and see what comes
out...

> Older remote diag stuff (L0006? in an 11/750) would certainly have had
> some odd, proprietary, possibly interactive method of communicating
> with Field Circus. I can imagine a human really dialling in and
> issuing interactive commands at an 11/750. By the time the VAX 6000
> came out, they probably wanted a program doing the low-level work,
> so they may have rolled out a networking protocol which is not
> based on human readable commands and <CRLF> command seperators, and
> that allows for in-band error detection - all the things we like
> about network protocols - automatic and robust, unlike throwing
> commands at a console prompt.
>
> > > As for running DDCMP over the console line, it's
> > > probably possible but usually not a good idea
> > > (the console line is usually deliberately pretty dumb,
> > > the principle being that it's harder to screw up that
> > > way).
> >
> > Wouldn't try it anyway. I have enough trouble with dumb serial lines!
>
> Not just dumb in the sense of a dumb terminal, but older VAX console
> lines tend to be resource hogs on the CPU, sometimes due to
> the interrupt level the UART comes in at, sometimes just due to
> the fact that it is a programmed-I/O device, not DMA like a DMF-32
> or other "TXDRIVER" (vs "TTDRIVER") compatible serial device.
>
> It's why I was happy to put that DMB32 of yours into my 8200 - I have
> four console serial lines to start with: OPA0 and three others.
> I have been told that they exact a toll on performance to use them
> heavily (Kermit and the like). The normal mode for a VAX was to
> stick a printing terminal on OPA0 and let it spill paper on the floor
> all day. Who cares if a 300 bps connection gets serviced at half
> the max transfer rate - it's not like a _user_ is waiting for the
> printing to finish. For output, the OS can pace the console printing
> and defer it until later, giving better response for the live humans on
> the other ports. Contrast how long it takes for an operator message to
> print vs. when the OS panics - with absolutely nothing better to do
> that scream for help, the console speed picks up - you can hear the
> change in the cadence. That's how we always knew the VAX crashed - by
ear.

Neat! Stuff like that is what's missing from modern computers-- they have
no personality, aside from an occasional bluescreen or fifty.

> -ethan

Bob
Received on Wed Jun 05 2002 - 20:45:19 BST