[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: 3.5 for 2c
In article <21d4mb$7p2@wraith.cs.uow.edu.au> david@wraith.cs.uow.edu.au (David E A Wilson) writes:
> dempson@swell.actrix.gen.nz (David Empson) writes:
>
> A very good summary of Apple's 3.5" drives and controllers. It should be
> added to the FAQ.
Thanks for the comment, and for the additional information.
I should also add a couple of points myself (thanks to unknown@apple.com):
- A UniDisk 3.5 can probably be used on a Mac if it is "lobotomized",
by removing the processor board from the drive and replacing it with
the equivalent interface hardware from an Apple 3.5 Drive. I haven't
seen inside a UniDisk 3.5, so I don't know exactly what is required here.
- Since the SuperDrive will work as a normal 800k drive, and they cost
exactly the same as the Apple 3.5 Drive, you might as well buy a
SuperDrive, even if your disk port only supports the Apple 3.5 Drive.
Note that this DOESN'T apply if your disk port only supports the
UniDisk 3.5!
> [Universal Disk Controller]
>
> Looking at the code it should work on a //gs. If it finds a 65816 then
> it plays with the //gs CPU speed register. Not the way I would have
> checked for a //gs! It relies on the following code not causing
> problems on a 6502/65c02:
>
> c61c clv
> c61d sep #0xea
> c61f nop
> c620 bvs 0xc629
Ick! Whose to say that the SEP opcode doesn't do anything on some
third-party 6502 (e.g. a Rockwell one)? There won't be a problem on a
65C02, since it treats unimplemented opcodes as NOPs (with a variable
number of clock cycles).
I sure hope it does a CLD instruction somewhere after the above!!!
(on the 65816, at least). This code will also detect a 65802 as
being a IIgs. On a IIe or IIc, $C036 will just click the speaker, so
there shouldn't be a problem (assuming it doesn't do anything more
fancy).
--
David Empson
dempson@swell.actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand