Re: 5.25" PROM Code Question

[Holger Picker <pickerh@uni-muenster.de>]

On Tue, 18 Feb 2003, Bryan Parkoff wrote:

> Date: Tue, 18 Feb 2003 17:26:07 -0600
> From: Bryan Parkoff <BParkoff@satx.rr.com>
> Newsgroups: comp.sys.apple2
> Subject: Re: 5.25" PROM Code Question
> > The loop synthesizes the 6-2 GCR decoding table in page 3.

> It does not make sense because there is no table in page 3.

Yes, there is. It's probably destroyed shortly after whatever boot program
on the disk has been executed, since the memory area $300-$3ff is used in
various ways, e.g. storing jump pointers to DOS 3.3 functions. Therefore, you
may not find it there later on, but it is definetely there when the slot rom
loads sector 0 of the first track (0). Note: This table is usually only used
on this special occasion, i.e. loading the RWTS image from disk. The RWTS
contains its own 6-2 GCR decoding table that will be used afterwards everytime
you read data from the disk.
Kind regards

  Holger