new disk controllers for DEC platforms (was Re: Q-bus to CF)

[Ethan Dicks]

On Sun, Mar 02, 2008 at 07:18:51AM -0800, Bob Armstrong wrote:
> > Ethan Dicks (ethan.dicks at usap.gov) wrote:
> >
> >>On Sat, Mar 01, 2008 at 08:35:14PM -0500, Charles H Dickman wrote:
> >>...
> >> Software development for a 20 year old OS is not easy.
> >
> >And in the case of the PDP-11, several 20-year-old OSes, or in the case
> >of the VAX, a few old OSes, of many versions.
> 
>   All true, although it might not be as bad as it sounds.  There are a lot
> of people on this list, and some of them used old DEC computers and
> operating systems.  Some of them might already know how to write a driver
> for one of these OSes - get a group of them together and you'll have all the
> old OSes covered.

True, but there are a lot of dusty neurons to polish before much progress
could be made.  I haven't written a device driver for DEC hardware in
over 15 years (I've worked on Ultrix, and VMS 4.x and VMS 5.x, myself).

> ... the first thing you should do is
> hack up simh to include emulation of your proposed new "RQATA" interface
> card; then you could start writing drivers before the hardware was even
> done, and simh is a great tool for debugging the driver software. 

That's an excellent suggestion (and I say that having helped Bob Supnik
debug one of _his_ drivers long ago).

>   OTOH, the SBC6120 was sort of my experiment in open source old computer
> development.  I always hoped people would expand and add to it, both in
> hardware and software, but for the most part that never really happened.
> Most people wanted to buy a turnkey system that they could plug in, turn on,
> and start using it - people seem to have jobs, families and real lives and
> just don't have the time to do a lot of development.  

>From my own standpoint, especially since I have an IOB6120 and FP6120,
it does pretty much everything I'd want it to do.  About the only feature
I can think of off the top of my head would be to jimmy the IOB6120
FPGA firmware to be able to talk to a real RX01/RX02 hanging off of the
I/O pins (with suitable line drivers/receivers, of course).  I'd probably
only want that to be able to image disks, anyway, though.  Out of the box,
the SBC6120 boots up OS/8 and that works for most of what I'd do with a
"real" PDP-8 anyway - boot it up, play a few games, and marvel at what's
going on under the hood.

In terms of software dev, folks can just as easily fire up simh and work
on software there.  I always thought the appeal of the SBC6120 was to
have a real 12-bit machine in ones hands, not the developement aspect of it.

-ethan

-- 
Ethan Dicks, A-333-S     Current South Pole Weather at  2-Mar-2008 at 15:49 Z
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Ethan.Dicks at usap.gov            http://penguincentral.com/penguincentral.html