8520/21

On 3/4/2015 1:47 PM, Gerrit Heitsch wrote:
>
> The 8520 had a normal timer instead of the RTC the 6526 had. That's 
> about it, you can use a 8520 in a C64 if the software doesn't use the 
> RTC.
I just continue to struggle with this.

I am not disputing that they are different, I just cannot understand why 
CSG would have taped out a simpler version of the 6526/8521 when they 
already had a die for the 6526. I can understand doing the work needed 
to move the 6526 into HCMOS II, but why not go straight to the 8521, so 
the resulting part could be used for the 64c/128/1571/1581/etc.

It just does not make sense.  It's like saying:  I am going to modify my 
iOS app for iOS8 and I am going to remove some key functionality, and 
retest the entire app, since that functionality could affect any part of 
the app.

There has got to be more to this story.  I don't buy that the TOD BCD 
stuff took up that much die real estate, and so I can't believe that the 
removal would have improved yield considerably.

Jim


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