sicklittlemonkey wrote:
Michael J. Mahon wrote:On the //c, the speaker is driven from an op amp on both the low-going and high-going toggles, so it is symmetrical.Thanks for the clarification. I was wondering what the chip in the schematics was. It seems that Apple fixed a some important things in the //c - even the firmware by revision 4! I like it more and more except for perhaps the interrupt complexity, and the few breaking changes they made, like the VBL' IO location.
One of the most practical improvements resulting from the audio op amp is that the audio output is now referenced to ground, so a "line/headphone out" jack was easy to do. But this improvement is more than compensated by the way they screwed up the pushbutton inputs. Prior to the //c, they were trivial to use, but multiplexing their function with mouse functions really messed them up on the //c for use as TTL inputs. It's almost as bad as the Platinum //e, where they just heavyhandedly shunted them to ground with 0.1uF caps! Fortunately, they are easy to cut out, restoring the pushbutton inputs to full functionality. -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."