PoOps "Figure 4-12. Format of the TOD Clock, ..." shows that SCK does
not affect the Epoch Index. "Additionally, the PTFF instruction [*may*]
manipulate the TOD clock and epoch index, ..." "may" or perhaps not?
I tired of searching before I found particulars of PTFF.
Is it anticipated that circa 2043 an updated OS will use a combination
of SCK and PTFF to set TOD and Epoch Index.
Does the Clock Comparator account for Epoch Index? What will happen
on that critical date circa 2043 if a programmer does a STIMER for
several hours?
• When the multiple-epoch facility is installed in the configuration,
the carry causes the epoch index to be incremented by 1. Any carry
propagated out of the leftmost bit position of the epoch index is ignored.
I'll conclude that if an inquisitive and privileged programmer sets
the Epoch Index and TOD to x'7F FFFF ..." and waits, the pair will
wrap to x'80 0000 ...."
I've long felt that the Epoch Index should be considered signed. It's
more useful to be able to represent times in the 19th Century than
in the 300th.
-- gil
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