Linards Ticmanis wrote:
David Wilson wrote:Linards Ticmanis wrote:It occurred to me though that I could simply have used a 2732 chip instead with a single external wire soldered to it, no need to use a real adapter or go hunting for exotic EPROMs, since half of the 2764 isn't used at all. Two Apple fonts occupy only 4K, not 8K.Each half of the 2764 (PAL IIe) chargen has one copy of the font (256x8=2048 bytes) plus another 2048 bytes of LORES & HIRES bit patterns (unlike the II(+) which generates the graphics with other logic).I found this out too shortly after I wrote the above... when my graphics were suddenly rendered useless because I had simply connected A11 to GND. Though I have to admit I don't quite understand the role of those patterns.
It just simplifies the logic and timing of the video generator by using the same data path for all modes. -michael NadaNet networking for Apple II computers! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."