Re: Detect a C128 from C64 mode

From: Segher Boessenkool <>
Date: Thu, 23 May 2013 21:33:14 +0200
Message-Id: <>
>> Does that matter?  The original test bit (in $d016) crashed the
>> system because it disabled the dynamic RAM refresh (therefore, it
>> was removed).
> You mean: There are chip revisions where the test bit actually does
> something? On my 6569 (datecode from early 1983), it was a no-op.

(reg $16 bit 5, "RESET").

Presumably it actually has function on the 6566.  On the 6569R1 it
is a register bit, but the metal track running from its output just
stops in the middle of nowhere.  It is going in the direction of
the X/Y counters; supposedly it reset those counters.  No 6566 die
pictures to check, unfortunately :-(

On the 8565 the register bit is still there, but the metal track has
been ripped out.


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Received on 2013-05-23 21:01:00

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