From: Ethan Dicks (ethan.dicks_at_gmail.com)
Date: 2007-08-24 17:39:45
On 8/24/07, ruud.baltissen@abp.nl <ruud.baltissen@abp.nl> wrote:
>
> Hallo allemaal,
Hallo, Ruud,
> ;** bytes for syntax check
> .BY $51, $DD, $1C, $9E, $1C
> ;
> ; ^ ^
> ; | |
> ; +-------------------+---- why are these here?
This I know nothing about.
> At $F10F a buffer is selected for loading the BAM. The result is always
> 13. IIRC the BAM was always loaded at $0700. Can anybody shine a light
> on this, please?
You might consider comparing this code to its equivalent in the
2040/3040/4040 codebase. I _think_ it's a simplification of the code
that once had to juggle BAMs for two floppies. I think what happened
was rather than rewrite this part of the code entirely, they removed
the part of the code that allowed either of the BAMs to float around
buffer memory on a dual drive. Why permanently lo ck out a block
buffer from use if you never (or rarely) use the second drive. My
memory of how people used the drives 25 years ago was to mostly use
drive 0 unless copying or running a business app that could use drive
1 for file storage (WordPro, hand-written REL file databases, etc), or
perhaps developing in assembler with the C= Macro Assembler (which
could be done with a single disk, but might have been easier with a
dual).
That's my conjecture based on some dim memories of the day, and a
little poking around in the disk drive code that I've done in the
past.
-ethan
Message was sent through the cbm-hackers mailing list
Archive generated by hypermail pre-2.1.8.