> 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 con

> 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.