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) ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html