On 2017-04-10, at 10:08, Tony Harminc wrote:
>         ...
>         STCK  DWORD               S/370 clock in IBM TOD units (bit 51 = 1uS)
>         LM    R14,R15,DWORD       TOD CLOCK UNITS in R14,R15
>         SRDL  R14,12              MICROSECONDS SINCE JAN 1, 1900
>         ...
> Of course the value in DWORD doesn't have to come directly from STCK. It
> can as well be a stored value, but take care that it's not before 1970...
>  
Are you concerned with bit 0 of the TOD clock's changing?  I think this
happens a little after 1970.  And the whole TOD clock resets in 2042
(? it's hard to find a reference.)

STCKE solves this for over another century, provided that IBM comes to
support the top byte in hardware and software.

-- gil

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