From: Gerrit Heitsch <>
Date: Sat, 23 Jul 2016 22:01:47 +0200
Message-ID: <>
On 07/23/2016 09:42 PM, Segher Boessenkool wrote:
> On Sat, Jul 23, 2016 at 09:16:18PM +0200, Gerrit Heitsch wrote:
>>>>> The visual6502 project has a die picture of an 8501.  From the picture
>>>>> it seems clear that both the 8500 (c64c) and 8502 (c128) used the same
>>>>> silicon, with different contacts bonded out.
>>>> You sure? The 8501 is missing Port-Bit 5. It's not only not bonded out,
>>>> it's not present, you can't set it while the 8500 has all the port bits,
>>>> you can set them.
>>> (bit 5?  Do you mean bit 7?)
>> No, the 8501 is missing Bit 5, Bit 6 and 7 are present and used. They
>> are used as inputs from the IEC bus. I assume since that makes is easy
>> to use the BIT command or ROL/ASL for serial/parallel conversion.
> Ah, yes, I should look more carefully at the die pic :-)

Which reminds me... we still don't have a die pic of a 8360R2... I only 
have a moderatly good one of the 8360R1.

>>> Why do you think you can set all port bits on the 8500?
>> Because people have been trying to use Bit 6 and 7 to determine CPU
>> temperature or detecting a 6510 or 8500 from the time it takes a 1 to
>> become a 0 when switching the port from output to input.
> It will be interesting to see what 8500 looks like, then.

I would assume like a 6510, just smaller since it's no longer NMOS but 
HMOS-II. I really doubt they made more changes than they really had to.


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Received on 2016-07-23 21:00:02

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