8 Aug
2014
8 Aug
'14
3:16 p.m.
-----Original Message-----
From: Dennis Boone <drb at msu.edu>
Sent: Aug 8, 2014 7:27 AM
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
Subject: Re: Vtserver, pdp11/34, and saving images
I am using a standard DL11-W for the TU-58 serial interface, but
modified it to support a 115.2kb data rate. This means that for
each incoming character the 11/34 has about 90usec or so to process
it. More than enough time to read it from the DL11-W, store it in memory,
manipulate some counters, etc.
The XXDP TU58 driver can handle this, as it is not interrupt driven,
it is polled. I haven't tried the RT-11 TU-58 driver at this rate, but it
may have issues as I believe it is interrupt driven. It would be an
interesting experiment.
On the host side I am using my TU58EM program on a PC. It can easily
handle the 115.2kb serial data rate.
This is a standard 11/34A with MS11-L MOS memory array, no cache option.
I have been using this configuration for a few weeks now and have seen
no issues at all in loading and running XXDP diagnostics from this
emulated TU58 device.
My mod is not specifically described, but there is at least one web page
out there that describes modding the DL11-W for higher baud rates. That
page described the crystal and divider changes, but did not go as far
as changing the UART to a newer version capable of 115.2Kb.
Don
At 9600b (max standard rate of a DL11-W) it is
not fast. However, a
DL11-W can be modded to support 115.2Kb fairly easily (new UART, remove
one chip in baud divider and replace with a wire, and a new crystal
oscillator). I have done this for my 11/34 and I can now boot XXDP in
about 15 seconds (vs 3 min at 9600b).
Don,
I'm curious about the details here. Can the /34 actually keep up doing
PIO at this rate? Or are you using DMA somehow? Is this vtserver or
one of the TU58 things or something else? 115.2k isn't one of the
results of the retrocmp.com mod; is yours described anywhere?