16 Oct
2012
16 Oct
'12
2:54 p.m.
On 16 October 2012 16:29, Rob Jarratt <robert.jarratt at ntlworld.com> wrote:
Hmm...
In terms of a "udisk" board, instead of re-inventing the wheel and
trying to rediscover all of the various controller information, could
one not attempt to reuse code from a software emulation of said
device? In other words, doing something like abusing the code of
SIMH's RQ, or RL driver into something usable by the electronics on
the board as a definition of the controller. If that could work, you
could easily cut down on the needing to re-invent the wheel with
regards to figuring out protocols. (Since if the protocol wasn't
written correctly enough for the emulator, software wouldn't run
correctly, or at all.)
Hmm... actually...
This is probably an unworkable idea, but I'll throw it out there any way...
How difficult a job would it be to "rip out" the CPU/bus
controller/memory code of SIMH, and replace it with an interface to a
real bus controller/listener program? This way you could keep the
already written and functional-in-the-eyes-of-the-original-software
device code, and you get a small plethora of devices.
If one wanted to have a nearly "truly universal" controller card, you
could make the card a relatively dumb device, with only the logic to
interface between the program and the QBUS/UNIBUS in the card, while
you have a bastardized SIMH sitting on a separate computer which let's
you have the machine see any controller you so choose to enable (11/83
with DECtape any one?).
Of course, that's just an idea, and probably a lousy one at that. But
I'm just putting it out there, since it popped into my head.
Cheers,
Christian
-----Original
Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Jay West
Sent: 16 October 2012 00:43
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: unibus to modern disk interface?
Most of the discussion on this that other people have brought up, is why I
liked Brad Parkers "udisk" approach so much. His design goals
were:
Create a low cost unibus adapter card which can emulate a small number of
popular controllers (RL11, UDA50, etc) and use an IDE or CF disk as the
actual media.
Make it easy for others to write personality modules for different
controllers.
Should allow use of a IDE/CF disk to boot a PDP-11 (or vax).
Specifically, I was enamored of the approach that allowed a user to write
their own personality module to change it from acting like a SCSI
controller
vs. SDI vs. etc.... all via software. This would
seem to me to be the most
functional approach for the most people.
I'll pony up a bounty of $300 to get someone to take those design goals
through to a kit form. Anyone want to add to the bounty? Or take up the
gauntlet? :)
J
I think there are actually two approaches, depending on what hardware you
have already.
The first is the udisk approach. That allows you to emulate any card for the
bus that the card is designed for. You would need different cards for Unibus
and for Qbus, and I suspect for some protocols like MSCP it the software
might be hard to write, not well documented etc.
The second is to emulate at the disk interface. For example the MFM
interface for RD53/54 like I am interested in, or SCSI. In this case you
need different cards for different interface technologies but could use
existing controller. I like this approach more because you have more of the
original hardware, but recognise that not everyone will have that hardware
(I have a few RQDX3, one KZQSA, but I don't have, and really want, a KFQSA).
I have a few RD53/54 that will last me a while but when they are gone they
are gone, and I find it increasingly hard to find sub 1GB 50-pin SCSI, so I
want to emulate at that level. Don't have the design ability really but I
may try to breadboard something some day. I think this solution may also be
easier to get parts for, particularly the line drivers, which seem to be
hard for Qbus.
Regards
Rob