Re: GSOS.P8.Anatomy

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

A2MG <a2mg@aol.com> wrote:

> At www.apple.com/macos/information/2000.html Apple Computer is telling
> people that they must have ProDos 2.00 or later for the year 2000, but
> they do not explain why. Does anyone know the exact reason for this
> (please feel free to be technical)?

I've just had a glance through ProDOS-8 technical note #23 (ProDOS-8
Changes and Minutia).  In the entry for P8 2.0.1, the following item
stands out:

   o   The Apple IIgs clock driver inside ProDOS 8 now limits the year
       to the range 00 through 99.

Implication: earlier versions will produce an invalid year on a IIgs for
2000 or later (probably uses 100 for 2000, when it should be 0).

Another relevant technote is ProDOS #28: ProDOS Dates--2000 and Beyond.
This defines what the 7-bit year field in the date is supposed to do
(valid range is 00-99 only; 40-99 are 19xx, 00-39 are 20xx).

It is possible that P8 2.0.x's Thunderclock driver has also been updated
to comply with this definition, though I can't see any mention of it.

The technote (#28) says that "current" versions of the operating systems
(8-bit and 16-bit) did not comply with the definition.  As of September
1990 (when the technote was written), the current version of P8 would
have been 1.9.

Some experimentation would seem to be in order.

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