Re: 5.25 drive emulator

[stu1222@discover.wright.edu (General Unix Accounts)]

In article <1994May19.233320.15374@labtam.labtam.oz.au> philip@labtam.oz.au writes:
>Ron "Asbestos" Dippold writes:
>
>>For a real 5.25 emulator, you'd need to intercept and emulate all the
>>bizarre Disk ][ ports and try to do something meaningful with them.
>
>  This wouldn't be impossible, but you would probably need to save your
>disk images as actual disk bytes so that you could emulate the raw reads
>and writes that the controller card does; this would increase the size
>of your disk image by a fair margin (approx. 350-400 bytes per sector
>rather than 256).  But I don't think the emulation would be all that
>difficult as long as you knew what the disk I/O locations did (I used to
>but it's being a while... :-)
>  The point is that just emulating a disk ][ controller and letting the
>original RWTS code (or whatever code is being used to access the disk ][
>controller) would be the most direct implementation, and it would in
>that case work for everything (or should, in theory).
>-- 
>=========== Philip Stephens, Systems Programmer, Labtam Australia ============

I got this in my mailbox:

------start of letter

Subject: Re: 5.25 drive emulator
Date: Thu, 19 May 94 14:23:45 MET DST
From: koch@informatik.uni-kl.de
 
You write:
>Ok, this is really getting on my nerves.  STM can do Apple II disk images
>on a mac and do a complete emulation.  Why cant anyone out there write a
>5.25 disk emulator for the GS?  This way we can store and run those
>classic 4,6,8, and 12 sided games off of a Hard Drive.  Also, those 5.25's
>that are sitting there in the dust are slowly demagnetizing themselves over
>time.
>
>I am not capable of writing something on this scale, but I know that there
>are programmers out there who can.  This would be a worth while project.
 
As a good starting point, you might use the source of my Apple ][+
emulator for Unix and X Windows. It has a full Disk ][ emulation.
 
Any disk, which is copyable by COPYA or FILER, will work. The
emulator uses disk images of 140kB with DOS 3.3 interleave (apl2-em format).
Disk data is encoded/decoded on the fly, while the Apple ][ hardware
locations are accessed. I have used DOS 3.3, ProDOS, Apple Pascal
and several "fast loading" games and all ran fine.
 
The Disk ][ emulation is written in C and highly portable. It should
be possible to compile it on a GS with only minor modifications.
 
Peter
------------------end of letter

So the next question is whether or not there is someone out there that
would be interested in writing such an emulator?  I wish I could.

                        Paul Zaleski