Re: upgrading smartport rom on //c

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <4p1k41$eua@goanna.cs.rmit.EDU.AU>,
Matt <mdj@arcadia.cs.rmit.edu.au> wrote:
> Hi,
> 	Since unidisk 3.5's are getting awful hard to find in this country
> nowadays, I was considering that if i could get hold of a dump of the
> smartport rom from a //gs or //c+, i could possibly write a rom to replace
> to //c smartport rom and thus utilize Apple 3.5's, which, incidentally,
> aren't too difficult to come by.

Sorry, not possible on a standard IIc.  The main reason that the IIc
only supports the UniDisk 3.5 is that the data transfer rate is half
that of the Apple 3.5 drive.  (The UniDisk is 4 microseconds per bit,
the same as a 5.25" drive, while the Apple 3.5 Drive is 2 microseconds
per bit).

You might be able to do it with an accelerated IIc.  The IIc+ has some
dedicated hardware to take some of the load off the CPU when accessing
an Apple 3.5 Drive (it could have probably managed without this if
Apple had decided to have an accelerated processor from the outset,
but the accelerator was added at a later point in the design).

Actually implementing support for the Apple 3.5 Drive would require
writing quite a lot of code, which makes use of poorly documented features
of the IWM and drive mechanism.  It might also be physically
impossible, because the necessary signals may not be available on the
drive connector.


Why not just exchange the IIc for a IIgs?


-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand