Re: 6567 revisions

From: Spiro Trikaliotis <*ml-cbmhackers_at_trikaliotis.net*> Date: Thu, 25 Aug 2011 21:12:42 +0200 Message-ID: <20110825191242.GA20368@trikaliotis.net> · ml-cbmhackers_at_trikaliotis.net

* On Thu, Aug 25, 2011 at 08:02:15PM +0300 Marko Mäkelä wrote:

> Hmm, now I got another question: What was the mysterious "always set  
> this bit to 0" in the VIC-II? Was it used in some early 6567 revision? I  
> do not remember any effect when I set it on any of the 6567 or 6569 that  
> I had.
>
>   D016       53270                 VIC Control Register
> 			    7-6    Unused
> 			    5      ALWAYS SET THIS BIT TO 0 !

As you know for sure, the PRG documents this as "RES" (Reset-) bit. If this bit would be set
to 1, the VIC should suppress its operations generating an output
signal, refresh of the DRAMs and access to the system bus.

As we all know, however, this is not true for the 6569. It might be true
for (some?) 6567 or even for the 6566? (Of course, not the DRAM refresh,
as this is not present on the 6566).

Perhaps, someone with an Ultimax machine might check if the bit has any
effect on the 6566?

Regards,
Spiro

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