[Coco] NitrOS-9 Year 2000+ changes

[Gene Heskett]

On Wednesday 13 March 2019 00:01:03 Stephen Fischer wrote:

> Can somebody confirm that
>
> Year 1999 = $63 and that the next year is:
>
> Year 2000 = $00.
>
> With 2019 being $13.
>
> Years between $64 (100) - $FF (255) are illegal.
>
> SHF
That, generally speaking, is an artifact of the clock chips of the day. 
None that I've encountered have ever counted in the year register, past 
$63 or 99 decimal. The software clock modeled that behavior, so it was 
needfull that we add, external to the 6 byte string os9 keeps in memory, 
not 1900, but 2000 when it rolled over and was reset to 00.  That took 
care of y2k. But there is another gotcha, the cause of which I've 
forgotten now but 2038 is a date stuck in my ancient memory now. To 
properly handle that, and keep the image in memory too, will require 
another byte in the memory image IIRC.  Others, by then will maybe come 
up with a different, better solution by then. rs disk basic will need 
its own fix, and I didn't worry about y2k and basic as I haven't used it 
since '87 or so. AIUI, the basic clock doesn't know about leap years or 
such, so that will likely need a new clock subroutine installed above 
disk basic.

Looking thru the copy of nitros9 I have here, Boisy has been there, so 
all history and comments related to y2k have been wiped clean as the new 
versions start in 2004 or so.  So I'm lost and 20 years later, none of 
it rings any bells to me.  Sorry.  But the comments on clock chips, 
because we all have got a lot of pre-1990 hardware yet should be valid. 
Will that old pmos stuff still be going in another 18 years? It has to 
be well up the tail end of that famous bathtub curve already.

For dw users, I even see a clock2 module that grabs the time from the 
host pc.  One fix I just thought of might be to do a short modulo 100 
loop by stashing the year in scratchpad, subbing 100 to see if it 
generates a borrow, if not inc a scratchpad, and loop back to sub 100, 
and when it fails, reload the saved year and add the incremented byte to 
the left byte of 1900. But thats a sw clock only fix.

I'm not going to worry about as I, like a lot of us, will be gone by 
then.  And I expect this group will by then have some younger, creative 
people who can handle it. There are several younger minds that have come 
on board in the last 10 years that could easily do it here already.

Cheers, Gene Heskett
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