Eric et al,
Thanks for your replies.??? The application is a very old network manager.
The obsolete communications device is a serial board.
It is not, however, a typical serial board.? The serial board performs certain
functions
of a proprietary protocol which is somewhat similar to frame relay.? The
interface
to this board is not through a standard I/O port (like 0x3f8) but is based on a
shared
memory area of frame buffers.?? The application software running on the PC
allocates
a frame buffer ( physically located in the comm board) and copies a 128 byte
frame
to the buffer.? The comms board then takes the frame and does some link level
processing
(ie makes sure a channel is open, etc, imagine frame relay or X.25 but
proprietary).
The application software knows nothing about the low level things happening on
the
comms link - all it knows is that when it has a frame to send it allocates a
chunk of
memory and when it sees a chunk of memory appear in the receive queue area that
is an incoming frame.
So what I would want to do is something along the lines of what Eric suggested
about the VGA-
a certain memory area is defined for this buffer transfer.? So the emulator
would then actually
process the information or perhaps just open a more standards-based channel
(pipe, socket,
whatever) towards a small program which would do the link level communications.
I took a look at QEMU and have a ways to go but the source does not look all
that big.
I was impressed at how quickly I got a Linux environment running on my PC..
Dave
-----Original Message-----
From: Eric Auer <[EMAIL PROTECTED]>
To: [email protected]
Sent: Fri, 8 Aug 2008 11:36 am
Subject: Re: [Freedos-user] Emulating obsolete HW in FreeDOS
Hi Dave,
Please explain that "obsolete peripheral communications device".
> 1)? Re write the application to use WATTCP or something similar.
If it is open source, you can do that.
> 2) Leave the application alone and modify the emulator
> (like VMWare Player) to provide a bridge between the fixed
> shared memory addresses and some sort of standard Windows
> (or even Linux) interfaces.
You cannot modify VMWare (closed source) but you can modify
Bochs, Qemu and Dosemu. The latter is only available in Linux
but it has a nice virtual hardware infrastructure. I once
planned to "write a TI Pro PC" set of hardware for it but of
course it is still a lot of work so I never got around doing
it. The TI Pro has non standard COM ports and a high end 3
plane special 720x350 RGB graphics card.
> Leaving the application alone has some benefits since it's
> pretty complex, brittle and old.
What exactly does that application do?
> So option 1 is pretty obvious and I could run the app either with
> FreeDOS booted directly on the hardware or booted on VMWare under
> Linux or Windows.
It makes a big difference whether you boot on hardware or VMWare.
> Option 2 is what I'm trying to explore -- has anyone had experience with
> this?? Does either VMWare or DOSEmu have capabilities in this area?
Both do, but as -you- do not have the vmware source code, you cannot
"help yourself and write hardware for vmware". You can write your
own hardware for dosemu, bochs and qemu, though :-).
> some sort of memory range which is shared between FreeDOS and the
> emulator which would then communicate to the outside world?
Look at the way the emulators support VGA graphics: DOS writes
to the virtual VGA RAM and the emulator calculates what you
would see on a real VGA and then shows that on your Linux or
Windows desktop in an image :-).
Note that VGA hardware is pretty complex so do not get scared
when you fail to understand the VGA emulation engine sources.
Eric
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