Re: TIMEMASTER problem

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

Laine Houghton <laine@rainbow.rmii.com> wrote:

> I believe your right. The patch was applied to Prodos 8. The year 
> lookup table is limited to 6 years.
> From observation it appears there was a cliche of engineers who were
> certain you will never need more than 640K and the Apple // can't
> last more than 6 years.

It is simpler than that.  When the ProDOS driver requests the time from
the ThunderClock, the clock does not tell the computer what year it is
(only the day of month, day of week and month).  A lookup table is used
to calculate the year based on these three parameters.  There is no way
that the operating system can uniquely identify more than six years (in
some cases, five years).

Some clock chips simply do not contain a year register.  I'm not sure if
this applies to the ThunderClock (and clones).

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