Prom dates, er codes

[Bruce Plecan]

As I understand proms, a 27C128, and 27128A are functionally
the same, meaning they share CMOS technology.
  Anything else may have a different programming voltage, and
maybe of a slower operating speed??..

  On the few 512 proms I've seen they have all been "27512s", with
no As or Cs?.   The ""s are cause I not absolutely sure of that.
Thanks     Again reference to gm type memcals
Bruce