lyricalnanoha wrote:
> 
> 
> On Sat, 10 Jan 2009, David Wilson wrote:
> 
>> On Jan 10, 9:58Â pm, "Michael J. Mahon"
 wrote:
>>> lyricalnanoha wrote:
>>>> This contains a program I wrote to cram DOS 3.3 into 256
fewer bytes 
>>>> (by
>>>> disabling format and revectoring a couple patches) so that
ProDOS need
>>>> not be overwritten. Â It's a SYS file, and runs from ProDOS 8. Â (I 
>>>> also
>>>> tested it under GS/OS 5.0.4) Â On the DOS 3.3 side of the disk is a 
>>>> file
>>>> RETURN TO PRODOS, which pokes in the MLI call for
"quit", then executes
>>>> it - proving that ProDOS is still fully available.
>>>
>>> DOS 3.3 will run happily in just 16KB...
>>
>> I was thinking that DOS and ProDOS did not overlap (P8 in language
>> card, DOS in 3rd quarter of RAM) but then I realized why lyricalnanoha
>> needed to do this - the ProDOS global page at BFxx would be
>> overwritten by a 48KB DOS (and who would want to run a 16 or 32KB DOS
>> on a machine with 48+KB?).
>>
>> Well done lyricalnanoha. I will have to try it out sometime.
>>
> 
> That's exactly it.  I just crammed the stuff that would load into the 
> ProDOS global page down into the BEAF-BEFF area, overwriting the format 
> code.
> 
> I did a further tweak later that uses the image from dos.system *before* 
> the jmp $9d84, instead of *after* as the first version, I want to primp 
> it up a bit before I release that as the second edition, mainly I want 
> to be able to format from both sides (for ProDOS I got HyperFormat).
> 
> Naturally I used Hybrid Create :P
> 
> -uso.

Why not save the global page in the high part of LC2, above the quit 
code?  You should have enough space for that plus a little extra.  You 
shouldn't have to alter DOS 3.3 at all, but you could add to DOS a BYE 
command that restored the global page and returned to ProDOS.

Cool stuff,

Dave...
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