Re: Weird IIgs Rom 01 bug

["Jayson Smith" <nospamratguyspambegone@nospamplease.bellsouth.ihatespam.net>]

I have just managed to shed some light on this.
Probably the real problem is that the peek/poke interface the original
Applesoft program offered to the clock and other battery ram settings was a
bit simplified.  I'm now betting that the real cause of the date rollover
bug is a byte rollover.  This is confirmed by the fact that Apple aparently
knew about this eventuality when they programmed the control panel.  In the
clock setting menu, the years 00-39 correspond to 2000-2039, and the years
40-99 correspond to 1940-1999.  Therefore, you can't even set the clock to
the year 2040 normally in the control panel.  If you set it to the last day
of the year 2039 and let it roll over, it'll go on into the year 2040, where
about a month and five days later it'll mess up big time.
The weird thing is that aparently the clock will go earlier than 1904.  An
attempt, using my own program, to set the clock to 1/1/1900 00:00:00 was
completely successful.  No idea how much further back the clock would go.
So it looks like the GS clock has a total range of 01/01/1900 00:00:00 to
02/06/2040 06:28:15.  However, the range which can be set in the control
panel is only 01/01/1940 00:00:00 to 12/31/2039 23:59:59.
Jayson.

"Jayson Smith" <nospamratguyspambegone@nospamplease.bellsouth.ihatespam.net>
wrote in message news:w7ldd.34071$pi7.27371@bignews4.bellsouth.net...
> Hi,
> I've been playing around with a program I have which lets blind people
> adjust control panel settings without having to go into the desk
accessory.
> I was fiddling around with the clock section, doing some peeking, poking
and
> setting of the clock and found some very weird behavior so I wrote a clock
> print/set program to discover exactly what happens.
> It seems that at least on the Rom 01 GS, at exactly 06:28:16 on 02/06/2040
> the time becomes 00:00:00 on 01/01/1904.  This happens no matter if you
set
> the clock to a date/time past that mark or if you set it a few seconds
> before and let it pass that time naturally.  Quite literally, one second
> it's 06:28:15 on 02/06/2040 and the next second it's 00:00:00 on
01/01/1904.
> I think this might happen once or twice more between then and the year
2155,
> the highest year the clock format could handle.  Setting the date to
> 12/31/2155 and the time to 23:59:59 yielded 23:59:59 on 07/27/1976 or
> something like that.
> Now I seriously doubt that there will be many IIgs's still functional in
the
> year 2040 but I just wanted to let people know about this weirdness and
see
> if anybody has any thoughts about what might be causing it.
> This is untested on a Rom 00 or 03 as I don't have those machines.  If
> anybody wants, I can send the Prodos Basic program I've been using for my
> experimentations.
> Jayson.
>
>
>