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From: davet@oakhill.UUCP (Dave Trissel)
Newsgroups: net.arch,net.micro.mac,net.micro.68k
Subject: Re: timing loops
Message-ID: <650@oakhill.UUCP>
Date: Sun, 23-Feb-86 02:37:35 EST
Article-I.D.: oakhill.650
Posted: Sun Feb 23 02:37:35 1986
Date-Received: Wed, 26-Feb-86 04:43:54 EST
References: <156@motatl.UUCP> <530@hoptoad.uucp> <2795@amdahl.UUCP> <221@myrias.UUCP> <2817@amdahl.UUCP> <689@well.UUCP>
Reply-To: davet@oakhill.UUCP (Dave Trissel)
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Organization: Motorola Inc. Austin, Tx
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In article <689@well.UUCP> farren@well.UUCP (Mike Farren) writes:

>>(S/370 architecturally has 244 picosecond resolution)
>
>   I admit to knowing little about the S/370, but a 4 GHz clock rate?
>Can someone verify this, please?   I don't remember seeing any microwave
>plumbing in a 370... :-)

Back when I was working with 370's as a systems programmer the time of day
(TOD) clock systems guaranteed that the resolution was greater than the
shortest possible instruction time.  In other words, you would always
get a unique value from the TOD clock even if you read it with back to back
store clock instructions.

What this indicated was that the clock resolution depended on the machine
model of 370.  The bottom line 370s (370/25 if I remember correctly) were
so slow that a clock frequency of several microseconds would have sufficed.

  --  Dave Trissel  Motorola Austin
  {seismo,ihnp4}!ut-sally!im4u!oakhill!davet