Apple II emulator running on original IBM PC

Spotted on comp.sys.apple2:

Very nice writeup, and the emulator looks great and shows impressive performance.


Indeed, a nice README there with some interesting implementation details.

back when we wrote this code Appler achieved 75% of the speed of a physical Apple ][ (which runs at 1 MHz) on a 4.75 MHz PC/XT

…individual emulation routines for each 256-byte page of the 6502 address space. These routines share the same instruction space used to implement the 6502 opcodes, occupying the second half of each 256-byte segment (so, the emulation routine for opcode $20 (JSR ) shares the same segment as the emulation routines for reading and writing at addresses $2000…$20FF.

At the time we wrote Appler we of course knew that the colors are supposed to be purple, blue, green, and orange, but we had never seen them displayed by an actual physical computer, because the Apple ][ displays that were available in Bulgaria were all monochrome-green. Alex looked at the schematics, and he used the actual resistor values of the DAC to calculate what the 4 primary colors should be.

Very nice debugger/front panel:

Some by-design not-a-bug artefacts: