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Two Freddie Chips Question...


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#26 ClausB OFFLINE  

ClausB

    Stargunner

  • 1,366 posts
  • Location:Michigan

Posted Sat May 27, 2017 12:41 PM

This might shed some light:

 

http://www.atarimuse...freddie-mcu.pdf



#27 guus.assmann OFFLINE  

guus.assmann

    Moonsweeper

  • 317 posts
  • Location:Netherlands City EDE

Posted Sat May 27, 2017 1:12 PM

The 7 or 8 bit refresh has to do with the memory chips.

Older DRAM's use 7 bit refresh.

The newer (and faster) ones had 8 bit refresh.

So some memory upgrades to 256K needed an extra bit for the refresh.

That was created using a counter.

Have a look at the attached schematics. (a rework from the original design)

 

So I assume that Atari was planning to use different memory chips and they would need another way of multiplexing.

Hence, two different Fraddy-chips.

 

BR/

Guus

 

Attached Files

  • Attached File  256K.pdf   36.38KB   34 downloads





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