follow-up on the blinkenlight console project
GOOI at oce.nl
Thu Sep 1 15:10:39 CDT 2005
I'd like to tell my update on the SIMH blinkenlight console project(s).
A year ago (or so), Vince and I developed the 6809 Core and I/O Boards.
To refresh your memory about this project: the 6809 Core Board runs an
application that communicates with a modified PDP-11 version of SIMH.
You connect the I/O Board to switches and LEDs that represent a PDP-11
console, in my project example an 11/40 console. This console is the
part that you had to do yourself, you could/can take a real console,
but as I said earlier, that's (perhaps) a waste of a good machine.
For this project, see www.pdp-11.nl/homebrew/startframe.html
I have a new application that takes the first project one step further.
The 6809 now simulates the PDP8 instruction set, and the I/O Board
simulates a complete pdp8/e console. See this project results on :
Especially the second "project" is nice (IMHO).
I can run SpaceWar in OS/8 on the 6809 !
During the workz I added an IDE hard disk interface to the I/O Board!
The pdp8/e simulation boots DMS or OS/8 from the CompactFlash card.
As the performance is not *that* good (...), I upgraded the Core Board
to run twice as fast.
You can do that upgrade too, if you have installed the 6809, 6850, and
6821 in sockets. Replace these 3 chips with their "B" version, and
replace the 4 MHz clock with an 8 MHz version. That's all!
The RAM chip(s) and the EPROM that was delivered in the kit are fast
enough to support this upgrade.
The initial load of the pdp8 software is not "user friendly".
I am thinking about a Floppy Expansion Board (FEB) that connects to the
Core Board through the PIA socket. The 68(B)21 is installed on the FEB.
The FEB has all parts to connect 2 or 3 floppy disk drives, which can be
8", 5.25", 3.5" or 3". I will test the 3.5" version, but expect the other
drives sizes to operate corretly too. The controller will be the 1793.
I intend to write the floppy disk drivers in the monitor, so you can use
the floppy disk also in the 6809 environment. From my hobby 20+ years ago
I have a self-written DOS, not compatible with FAT-12. Sorry, the PC was
just 1 or 2 years old when I wrote that DOS. However, "my DOS" has all
the commands you'd expect.
I can make the FEB just for myself, but if there is more interest on this
follow-up project, I will document this work-in-progress better than I'd
do just for myself ...
An other thing I am thinking about, is a new design of the Core Board to
get a better performance for the pdp8/e simulation. I am looking into the
possibility what speed improvements this sim would get if I rewrote the
6809 pdp8/e code into 68000. The new Core Board will of course have an
68000 (or cost reducing) 68008 clocked at 10 MHz.
Any comment is welcome, but I will ignore proposals for CPLD, Atmel, etc.
enjoy the pdp8/e simulation webpage!
- Henk, PA8PDP. what's in a callsign :-)
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