It's pretty hard to find any specific information on the Apple III Plus. How did it differ from the original Apple III? I assume it didn't have those infamous heat-related reliability problems? Anything else?

Edit: To be more specific, are there any ROM differences? Any differences in the memory map, new or changed soft switches, new hardware registers? Any differences in the Apple II emulation?

In short, are there any software-visible changes?

Regarding added hardware such as the clock mentioned in the answer, is it directly compatible to stuff that was available as a plug in card for the older model? Are there fewer slots because of it?

And: is there any material online regarding any of those changes?

  • 1
    The original question seemed to have been answered by Raffzahn. The additional questions in the last edit are bordering upon "mission creep"... Jul 15, 2023 at 9:55
  • 1
    Concur with @Greenonline there, it may have been better to ask a new question for that extra stuff.
    – paxdiablo
    Jul 17, 2023 at 2:25
  • I admit I should have worded the question like that in the first place since this was the stuff I was actually interested in. Well maybe I’ll ask a new question at some later time
    – TeaRex
    Jul 17, 2023 at 8:55

1 Answer 1


Most important changes:

  • 55-watt power supply,
  • 256 KB of RAM as base size,
  • A new keyboard (Much like the later IIe),
  • clock included (built in),
  • standard port connectors.
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    Also, an interlaced video interface, and a better PCB (books.google.ch/books?id=fC4EAAAAMBAJ&pg=PA17)
    – airman
    Jul 12, 2023 at 18:20
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    Might be worth specifying the actual change, such as "55W power supply instead of a 45MW electricity substation".
    – paxdiablo
    Jul 13, 2023 at 1:30
  • Thanks for the great answer!! I expanded the question a little bit - feel free to answer those too if you like to...
    – TeaRex
    Jul 14, 2023 at 7:47

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