In <[EMAIL PROTECTED]>, on 04/17/2006
at 12:19 AM, "Joel C. Ewing" <[EMAIL PROTECTED]> said:
>On the original S/360 introduced in 1964, I believe a System Timer,
>which also required periodic interrupt servicing, was used to track
>clock time and it had similar drift problems.
The interval timer caused interference with memory accesses, which was
more of a problem for I/O channels than for the CPU. It was an
autodecrement word in low storage, and caused an interrupt when it hit
zero. The largest possible interval was a matter of hours, so OS/360
used something called the 6-hour pseudo clock to deal with wraparound
issues.
>I believe the hardware TOD clock was introduced
>with the following IBM S/370 architecture, so it has been around for
>at least 30 years.
Yes, unless it came in with the 360/85, but in many ways that was a
prototype of the S/370.
--
Shmuel (Seymour J.) Metz, SysProg and JOAT
ISO position; see <http://patriot.net/~shmuel/resume/brief.html>
We don't care. We don't have to care, we're Congress.
(S877: The Shut up and Eat Your spam act of 2003)
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