Re: 6526A synchronous serial behavior?

From: Gerrit Heitsch <>
Date: Fri, 23 Sep 2011 16:54:29 +0200
Message-ID: <>
On 09/22/2011 10:25 PM, Nate Lawson wrote:
> I would think all 1571 drives have a 6526A because they have to run at 2 MHz. The 6526 can only do 1 MHz. As for the 8520, it would be strange to move to the HMOS line in only this chip.

Not quite.. I have a (currently defective) 1571 that contains an 8521R0 
instead of a 6526A. I also own a C64 board (250466) that has a 8521R0 on 
position U2. On position U1 this board has a 6526A. From the looks, this 
is how the board was delivered.

The interesting question is... Does the 8521 behave like a 6526 or like 
a 6526A?

Also, there is a 6526B (3MHz?), I own one with a datecode 4887.

There is also this information:


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Received on 2011-09-23 15:00:03

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