Hi, congratulations, that looks realy nice, Im luckey enough to have some
real mass storage but still looking forward to trying it out, rerpaired an
M 8655 to be ready :)
I think the guys over in the Vintage Computer DEC Forum would be well
interested in this, could you do a post there ? or I can if you would like.
Dave H
----- Original Message -----
From: "Kyle Owen" <kylevowen at gmail.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Wednesday, February 05, 2014 7:16 AM
Subject: Booting OS/8 on a PDP-8/E from a PC
Greetings,
I've been hard at work on an OS/8 system handler that negotiates block
transfers between a PC running a special disk server. The two are
currently
working great! I was able to use the BUILD utility to make my own OS/8 V3D
disk and boot from it. I then thought that it may be possible to take an
existing RK05 image and replace the bootloader and system handler with my
own. Sure enough, it works!
Check it out:
https://www.youtube.com/watch?v=YkqVJ6ShV5A
I'll be releasing the source code for all of this within the next few
weeks
as I make minor changes (and mostly tidy it up).
A few details: the handler resides in one page and talks to the server to
negotiate the transferring of pages. To keep the handler small, I'm
offloading as much stuff onto the PC as possible. There's no error
detecting (although this hasn't been an issue for the millions of bits
I've
sent thus far) and the features of the handler are pretty basic. The disk
server is written entirely in C and has been successfully compiled on Mac
OS X and Windows under Cygwin.
The handler sends serial data to an M8650YA (currently addressed at 40/41,
the aux TTY addresses) operating at 19200 baud. This is pretty slow still,
as you can see from the video. But it's usable! And it's bound to get
better with a few more improvements.
To bootstrap the system, the RIM loader is toggled in as the primary
bootloader, and a secondary bootloader is sent in RIM format. Start the
system at 0020 after that, and it'll boot right up.
In summary, anyone with a spare M8650, M8655, or other serial card can now
boot OS/8, even if you don't have an RK05, DECtape, RX01/02, etc.! If you
have a parallel I/O card, another handler could be made for even faster
transfers, I imagine. This would require some extra hardware, though.
Let me know if you have any questions. Again, I'll see about distributing
the source in a couple of weeks, or as I have time.
Kyle
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