From: mitch2gs@hotmail.com   
      
       Question: How *exactly* does an Apple IIGS emulate the 8-bit Apple IIe?   
      
       For decades the answer has seemingly been the Mega II chip, essentially   
   an entire 8-bit Apple IIe computer on a single chip (minus the CPU, RAM   
   and ROM). In fact Apple's marketing and technical documentation always   
   pointed to the Mega II as how the Apple IIGS was backwards compatible.   
      
       I've always know the Mega II is what provides classic Apple II video   
   modes for the IIGS (40/80 ASCII, including Mousetext and international   
   symbols, LR, HR, DLR, DHR). And while some functions are not used   
   such as its keyboard control and mouse support, I just assumed the rest   
   was responsible for the Apple IIGS's 8-bit emulation mode....   
      
       Then I saw James Lewis' project to build a single chip Apple II, and   
   read his claim the Mega II's primary (sole?) function is to provides 8-bit   
   video modes. So, that got me curious. What, exactly, is allowing the   
   IIGS to emulate the Apple IIe? Such as its sound generation, or replicating   
   the MMU, IOU and various other components? Is it simply the FPI/CYA   
   chipset and some other TTL logic recreating the Apple IIe? If none of it   
   is coming from the Mega II, I'm looking for the real nitty gritty in terms of   
   technical details on how the Apple IIGS emulates an Apple IIe.   
      
       On a side note, if the Mega II was NOT responsible for Apple IIe   
   emulation, and mainly just used as an I/O controller that bottlenecked   
   the IIGS bus and video draws to 1 MHz, one questions why on earth   
   Apple didn't scrap the Mega II and design a replacement chip for the   
   IIGS in all those years? It seems like it was added to the IIGS simply   
   because it happened to be sitting unused in Apple's development   
   tool box (the Mega II was originally developed for other purposes).   
      
   Mitchell Spector   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)