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The Byte Attic

Modern replacement for 'Sally' CPU

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Is there interest in the community for a little board, built entirely with general-purpose, currently-manufactured parts, which replaces the 'Sally' custom CPU in the 8-bit systems? Here is a video of the reverse-engineering and design process:

https://youtu.be/iTJLFSFqFeE

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Well, new/old-stock SALLY chips can be purchased from Best Electronics for $8 each, so there’s likely not a huge demand for any kind of replacement right now.

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On 7/29/2020 at 7:36 PM, The Byte Attic said:

Is there interest in the community for a little board, built entirely with general-purpose, currently-manufactured parts, which replaces the 'Sally' custom CPU in the 8-bit systems? Here is a video of the reverse-engineering and design process:

Maybe there'd be more interest for a 65C816 replacement for Sally (there is one for the "normal" 6502 that fits in the Apple II). In a perfect world it would have RAM as well and all RAM access beyond Bank 0 would go to onboard RAM.

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The main feature of Sally is just having the HALT line that isn't in a normal 6502, right? I guess it depends on if you can make RDY work like HALT. Doesn't HALT work by stopping the CPU, but RDY just pauses a bus access for slow memory? So I'm going to guess that RDY doesn't free up the address bus. But it seems that on the 65816 there's the BE pin which will disable the address buss.

 

So I guess it would be do-able as a plug-in replacement with a 65816. It's just not worth the effort with a plain 6502 because Best Electronics still has plenty. And I can see how 8-bit users might want one.

 

And in fact, I found this thread:

 

Here is someone trying the reverse, a 6502C in place of a 6502:

http://forum.6502.org/viewtopic.php?f=4&t=4190

 

And here is some information about Sally:

http://ushomeautomation.com/Projects/Atari/65816.html

 

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