Regarding the Atari 800...
What's the difference between the 6502A and the 'Sally'? Is it simply a revision, or do the changes improve performance?
It seems the 6502C "Sally" added a HALT pin to allow Atari to remove four support chips and thereby build cost-reduced versions of the Atari 400 and 800.
answered Apr 23 '16 at 0:21
PIN 35 on the SALLY used HALT. There were other advantages. The Wikipedia article is pretty thorough. HALT was used so the ANTIC/GTIA graphics chips could halt the 6502 easier since they shared the same bus.
The SALLY was used in the Atari XL and XE 8-bit computer line, not to mention the 5200 SuperSystem and the 7800 ProSystem gaming consoles.
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Could improve this answer by proving links to the wikipedia article or (better yet) specific sections that highlight some of the advantages? – bjb Jan 29 '19 at 18:40
