Archive for the 'Apple II Technical Info' Category

A2 Diagnostic

Sunday, September 9th, 2018

Apple Internal Diagnostic Routines Apple IIgs The Apple IIgs has a fairly extensive inbuilt diagnostic program that is easily accessed at power up by holding the Open-Apple & Option keys when turning on the power, or at any time when pressing Control – Open-Apple – Option – Reset. #Name$Location 1 ROM Checksum $FF/7CAE 2 RAM […]

IIgs Bus Timing

Sunday, September 9th, 2018

The IIgs has two memory clocks: the processor (65816) bus, which connects to the Fast RAM, and the Mega II (Apple II-compatible) bus, which connects to the Slow RAM and peripherals. The 816 bus clock is identified by the symbol ?2 and the M2 bus clock is identified by ?0. The complement of the M2 […]