3 Jun
2005
3 Jun
'05
12:43 p.m.
Subject: Re: Simulated disk drive for RT-11?
From: Ethan Dicks <ethan.dicks at gmail.com>
Date: Fri, 03 Jun 2005 12:39:28 -0500
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
On 6/3/05, David Betz <dbetz at xlisper.mv.com> wrote:
RSP and MRSP are stock firmware. But as you said it's poorly
documented even in the EK-OTU58-TM-002 tech manual I have.
Does the TU-58 use a standard RS-232 serial
interface?
Yes. The TU58 drive is strappable, but 38Kbps is a standard speed.
Is the protocol defined somewhere?
Yes... I know it's written up in several DEC manuals, some of which
are probably on bitsavers. The basic protocol is called "Radial
Serial Protocol" (RSP), but, I think, for newer implementations, like
in the firmware of a VAX-11/750, there are some variations that, while
documented, aren't as easy to find as the base documentation. It's ordinary to hook a real TU58 on a port of a
DLJ11J... one can
even use a straight-through 10-pin Berg cable - it's the same pinout
(one of DEC's standards). It's also possible to emulate a TU58 on a
modern PC, or to hook up a real TU58 to a modern machine to read
tapes.
I don't have my tools with me, but googling for TU58 and emulator will
probably cough up something interesting.
Media size is a bit of a problem - a real TU58 is kinda small, even
compared to an 8" floppy. Speed isn't great - at least an emulated
drive doesn't have seek delays, but transfer speed becomes the
bottleneck.
At 256k per drive it's essentally an RX01 only slower. For RT11
thats a usable configuration.
One trick to speed things up is if the CPU has enough ram (256k is
enough and 1mb really works) is to run the RT11 VM: driver that's
the virtual disk driver (ramdisk). Load it with a copy of
everything then boot it then the tape/tu58 becomes seconday
storage and you have more space. Makes using a TU58 much
friendlier. The boot time for that is rather long.
OTOH, there are drivers for RT-11, and it _is_ a simple
device to
emulate. If only it were a few megs in size, it would be adequate for
quite a few applications.
There is a PC/DOS version that emulates a TU58 using the PC as a
disk rather than tape. I think Bob at sparetime gizmos has the code
but I could be wrong.
Allison