Re: Y1.999K problem

[mjmahon@aol.com (MJMahon)]

dempson@actrix.gen.nz (David Empson) replied:



>ISCA AppleII Librarian <apple2pd@ground.ecn.uiowa.edu> wrote:

>> My back-up plan is to extract the clock driver code from a patched ProDOS
>> (I hope the year table is in the driver code, can anyone confirm?).
>
>Yes, it is.  The clock driver is located by following the JMP
>instruction in the global page ($BF06).  The exact length is not
>specified, but it can be up to 125 bytes long.

It's at $D742, if I remember right--and it can _unoficially_ be
several bytes longer than 125.  (I think my _special_ clock driver
is about 137 bytes...  ;-)

>You should be able to compare the contents of a pre-patch and post-patch
>version of the driver.  I think the patch just updates the 7-byte table
>that is used to calculate the year, which is near the end of the driver.

That is correct.  Only the table bytes are updated, and the bytes
are "year numbers":  e.g.  99, 00, 01,..  but, of cource, not in that
order.

-michael

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