On Wed, 12 Jun 2024 11:55:57 +0000, Peter Relson wrote: > ><snip> >Am I correct in understanding that the Clock Comparator remains in 64-bit >TOD format? How will intervals spanning that time in 2042 be handled? ></snip> >Yes, it is true. The short answer to the second question is "correctly". >As a hint, try doing 64-bit arithmetic that subtracts a before-wrap 8-byte TOD >value from an after-wrap 8-byte TOD value and see what you get. > Thanks.
I can do that mentally. Suppose Subtract Logical or ignore overflow then then test only the sign bit. That amounts to a 142-year window centered on the current time. Rely on SL, not CL. I had wondered whether a programmer who naively loads the comparator with x'FFFFFFFF' expecting no expiration before 2042, or with 0 expecting immediate expiration would be rudely surprised. The answer is, "Don't do that!" -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
