What Is This?
This is a commercial package which provides a
complete emulation of a 6809 processor based computer system, running the
TSC FLEX operating system over the Percom PSYMON monitor ROM with a useful
command extension set. It runs under Win95; an older version is also
available to run under the Amiga's OS (2.04 or higher). On a modern PC
(Such as a Pentium, 60 mhz or better) the emulator is faster than the
original computer system was.
The 6809 is a 64k memory capable microprocessor with a decent register set
and a very strong instruction set for an 8-bit mcpu of its day.
Motorola was the source of the design of the 6809; it was derived, somewhat
loosely, from the 6800 and offered source code compatibility for the most part.
The next step beyond the 6809 was the 68000 series.
FLEX is a small (Approximately 6k!) disk operating system (DOS) which, along
with CP/M and a few others, truly pioneered small personal computers. These
were the systems that were already well in place when Apple Computer started in a garage.
We're all tired of hearing about how Apple "started" the computer revolution.
They didn't. They weren't even there at the time. Intel & MITS (the Altair 8800)
started it. Period.
PSYMON is a low level system monitor that nominally is 1k. In this emulator,
there is an additional 1k ROM extension which I created. It provides some
additional capabilities to the monitor.
When I call the emulation "complete", I mean that I've provided...
- A very comprehensive emulation of the original computer system.
- All the commands and utilities you'd need to do real work.
- Solid emulation.
- Usable speed.
If you ran FLEX in the past, you'll likely experience a strong sense of
nostalgia within seconds after starting the software. Welcome to the club!
For the future, I hope to continue to provide more FLEX commands and other
useful items to enhance the overall usability of the package.
This software provides emulation of all 6809 official* instructions with
the exception of "CWAI" & "SYNC". The virtual computer which the emulator
creates has 64k of memory, 2k of which is "ROM", or read-only. There is also
a low-level "monitor"; this is called "PSYMON". It originally came from Percom
corporation.
*
| There are some undocumented instructions that work, or partially work, within
some versions of the 6809 chips. These are NOT supported in the emulator; Motorola,
the architects of the 6809, never supported or admitted to these various operations.
Software that depends on these features will not function as intended. Also, Hitachi
created a chip called the "6309" which had some additional functionality. This is not
emulated at this time.
| |
The software provides character I/O via emulation of a Motorola 6850 ACIA chip located
at addresses $E008 and $E009, and aliased at $E004 & $E005. It provides Disk I/O via
emulation of a powerful DMA disk controller that lets the Host do 99% of the work
using the Host processor directly, which means that disk I/O is considerably faster
under the emulation than it was for any conceivable 6809 system.
Unfortunately, this is pretty well hidden by the enormous amount of work that the
emulation itself must do unless you have a reasonably modern processor (Pentium @
60 Mhz or better). Printer support is likewise handled by the Host processor directly
as a DMA operation. Under FLEX, you just use the "P" command as you usually would.
There is a menu that allows selection of LPT1 through LPT4 as the output printer.