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From: neil@amiga.UUCP (Neil Katin)
Newsgroups: net.micro.amiga
Subject: Re: 50 Hz problem with CIA's TOD
Message-ID: <927@amiga.amiga.UUCP>
Date: Sun, 30-Mar-86 12:34:08 EST
Article-I.D.: amiga.927
Posted: Sun Mar 30 12:34:08 1986
Date-Received: Wed, 2-Apr-86 02:44:42 EST
References: <1635@caip.RUTGERS.EDU>
Reply-To: neil@rocky.UUCP (Neil Katin)
Organization: Commodore-Amiga Inc., 983 University Ave #D, Los Gatos CA 95030
Lines: 38

In article <1635@caip.RUTGERS.EDU> #D2S%DDATHD21@WISCVM.WISC.EDU writes:
>It's some time ago, that <CB> found out, that the AMIGA clock is too
>slow. We found out, that it is 10 Hz too slow. People at Amiga (or was
>it Commodore ?) thought, it would be less expensive to use the AC-frq
>as the CIA's real time clock. OK, it works (not very precise, but it
>works - works with US-60 Hz.
>In 'good ole Germany' we have 50 Hz, which is 10 Hz less. Trying to
>change the 50/60 Hz-Bit in 68000 failed. Does the workbench clock set
>the CIA's TOD to 60 Hz or did I something wrong ?
>Anyway, It would be a great help, if someone of you could tell us how
>to make that clock run at the richt speed.
>
>                so long       Kosta
>
>BITNET: #D2S@DDATHD21                    < Show me Your disclaimer and >
>ARPA  : #D2S%DDATHD21 at wiscvm.wisc.edu < I tell You who You are...   >
>                                             <CB>'s std. disclaimer!

Sigh.  Your clock is not too slow, your software is too old.  The
1.2 software dynamically figures out your line frequency and sets
the appropriate constants for the timer.

The reason why we used AC line frequency is because, over long periods
of time, it is MORE precise.  In the US it is guaranteed to be stable
to a few parts in a million over 24 hours.  We were told that the same
was true in Europe.  Other periodic timers (such as vertical blank) may
vary up to 2%.  The current timer is good to 5 seconds a day.  Thats
equivalent to .005%.

In Europe, 1.2 prereleases are available from Gail Wellington, Commodore
Electronics, Maidenhead UK.  The phone number is 44-628-757-12.  In the
US prereleases are available to all registered developers through the
normal support channels.  If you have trouble getting it, let us at
Commodore-Amiga know and we will do what we can to get it straightened
out.

	Neil Katin
	pyramid!amiga!neil