4 ms·

Keep in mind the Apple II was designed in 1977 by a cash-strapped college dropout from off-the-shelf parts. Fast RAM for video didn’t exist. Classic Apple multi

• duskwuff 3y ago
  > from off-the-shelf parts This was the most serious constraint. Aside from the 6502 CPU, its memory, and the ROMs, everything on the original Apple II was constructed from simple, off-the-shelf logic ICs. No custom ICs besides the ROM; no highly integrated parts besides the CPU. You can still buy all the parts to build one yourself. Later versions of the Apple II replaced increasing amounts of the discrete logic with custom ICs, but the basic principles of operation (and the limitations that came with them) remained the same.
  • PhasmaFelis 3y ago
    Building an Apple II from scratch would be an interesting project.
    • nxobject 3y ago
      IIRC, you even got the schematics in the manual.
    • duskwuff 3y ago
      It's totally feasible, too. Here's some information from someone who used to sell kits: http://www.willegal.net/appleii/appleii-kit.htm http://www.willegal.net/appleii/appleii-kit.htm
• tom_ 3y ago
  It sort-of did have fast RAM for video! The chips used could do 2e6 bytes/second, or thereabouts, of which the CPU could demand just ~1e6 (or near enough), at predictable regular intervals. The remainder is entirely free for the video system! (This was a very common arrangement for the 6502, as it has predictable data bus accesses.) I'm not especially familiar with the Apple II's graphics capabilities, but it sounds like all its various modes need ~1 byte/microsecond for the visible period, so this would work out.