Re: CIA TOD Alarm Bug

From: Segher Boessenkool <segher_at_kernel.crashing.org>
Date: Thu, 9 Mar 2017 18:06:47 -0600
Message-ID: <20170310000647.GF31469@gate.crashing.org>
On Thu, Mar 09, 2017 at 11:37:31PM +0100, groepaz@gmx.net wrote:
> On Thursday 09 March 2017, 16:12:46 Segher Boessenkool 
> <segher@kernel.crashing.org> wrote:
> > On Wed, Mar 08, 2017 at 06:45:01PM +0100, groepaz@gmx.net wrote:
> > > i am investigating differences in the CIA behaviours (NMOS vs HMOS
> > > versions, ie 6526 vs 8521) at the moment. one thing that is pretty
> > > unclear to me, is a supposed bug in the TOD alarm behaviour. i can find
> > > some references to it on the web, which somehow look like one copied from
> > > the other to me - without
> > > ever mentioning the exact details:
> > There also is 8520.  I haven't yet seen good pictures of the 8521, but
> > the pictures that are there show that 8520 and 8521 are nothing alike
> > (and neither is like the 6526, either -- in the physical layout anyway).
> 
> 8520 is irrelevant in this context - the "TOD" is completely different 
> afterall :)

It is relevant in that until a few weeks ago  I (like most people)
believed that 8520 and 8521 are very similar.  They are not, making
the analysis of the 8520 (for which we do have good pictures) pretty
useless for deriving 8521 behaviour.


Segher

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Received on 2017-03-10 01:00:02

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