README file for yae, my Unix Apple ][ emulator

This is a test version of my Unix based Apple II emulator. Since it is under construction, it looks terrible :). To run the emulator you need two files APPLE.ROM and DISK.ROM. The first one contains the ROM image of the addresses $D000-$FFFF and the other contains the ROM image of the Disk II controller card in $C600-$C6FF. These files must be in the current working directory.

Notes:

CPU This is a Apple ][+ with 64K RAM. However, the CPU implements the 65C02 instruction set. PRODOS 4.0.2 boots fine in the emulator. There is a minor bug in BCD arithmatics. But most softwares tested run correctly. (Many games use BCD in score calculation.)
The emulator keeps track of cycle count though it is not 100% accurate. This is good enough for sound synthesis. Interrupt mechanism is possible though not complete. The 65C02 emulator core is written in optimized C. Condition codes frequently used, i.e. C, N and Z, can be calculated in one or two machine instructions in most cases with common C compilers. The main emulation loop is also structured for speed.
Disk The emulator currently supports one disk drive in slot 6. It uses 143K DOS 3.3 sector order images (DO). Write protection is done using chmod. The emulator saves to images. However, if you do anything which would corrupt a real disk on a real Apple (e.g. pressing RESET while writing), you may corrupt a disk image. The F1 key is used for re-mounting disk. Boot disk is specified in command line. For example
apple2.sparc foo.dsk
Graphics Text, Loweres and mono Hires are supported right now. Will do colour Hires later. Needs improvement in performance. Custom X fonts have been made and will be used later to improve communication efficiency between the emulator and the X server.
Keyboard The keyboard supports buffering. Since lower case is the norm in the Unix world, the upper case and the lower case are swapped in the emulator. Use Shift or Caps Lock for lower case.
Special keys
- Ctrl-Del reset.
- F1 mount/unmount disk.
- F2 shut down the emulator.
- left Meta key left Apple Key (For ][e emulation in future)
- right Meta key right Apple Key
Joystick The mouse is mapped to the Apple II Joystick. The PDL() functions return the relative position of the mouse pointer to the upper left corner of screen.
Audio The emulator supports some Sun (8kHz sampling) and Silicon Graphics (16kHz smapling) workstations with audio hardwares.
Compiler The emulator translates on the fly 6502 machine code into equivalent SPARC or MIPS RISC (SGI & DECstation) machine code. The compiler is far from optimizing though it is working. Depending on applications, the emulator speeds up from 20%-100% with the compiler turned on. It is not a big win though, if you are running very graphics intensive programs. The overhead of X makes improvement due to the compiler marginal.
GUI A Motif wrapper exits but it is decoupled for the time being.
Sources Messy. Mostly written in C but with some assembly programming in the run-time code generator. The sources of the basic emulator (no compiler) is available here in HKU and at wilbur. Look for the file yae.tar.gz in /pub/emulators/apple2/incoming at wilbur.
Bug reports & Comments Please send bug reports or comments to me. My email address is
ctkwan@cs.hku.hk