Sean Fahey wrote:
Michael J. Mahon wrote:Maybe - but I expect the plan was to attempt to use parts and tech already on hand before doing something custom.No, the only motivation--besides climbing the mountain because it's there--would have been to save the price of a UART.Ok, I'll add what I thought was implied...I expect the plan was to attempt to use parts and tech already on hand before doing something custom to save money.
My mistake--the copyright date on the card appears to be 1978 (1976??), and the earliest preliminary 6551 datasheet I can find is 12/80! So apparently, UARTs weren't available when this board was designed! This provides interesting historical context for the game port serial interface hack--it wasn't just a money-saver. ;-) -michael Music synthesis for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."