NEStra version 0.66 of December 14, 1999
Nestra is a Nintendo Entertainment System emulator, which uses x86 assembly language optimizations and code translation to achieve fast emulation with relatively modest CPU requirements.
To compile, simply run make.
Keyboard control is as follows. Change it if you want (in x11.c):
Arrow keys - move
Space Bar - Button A
Z,X,D - Button B Tab - Select Return - Start Pause/Break- Reset Escape - Exit
Emulation speed can be adjusted by pressing the numbers 1 thru 8, with 1 being normal speed and 2 being double speed, etc. This is helpful for skipping thru boring intros and such. Pressing ` will run the emulator at half-speed. Zero makes it stop.
Emulation speed is regulated by the system clock and not the CPU speed. If the CPU is unable to draw a frame within the scheduled time, the emulator will skip frames to catch up to the correct timing.
If the game uses save memory, this data is stored in the same directory as the ROM image, unless the directory ~/.nestra exists, in which case all save files will be stored there instead. This allows different users to each have their own saved games.
On 8-bit displays, normally only the minimum number of colors are allocated. This is sufficient for most games, however if you experience color flickering, you may need to use the -s option to allocate the full color palette.
The program works as follows: The compiler translates the 6502 code to native code and executes it. The translated code then calls the input/output functions as necessary.
This was developed on Linux/x86, and users have reported that it works with FreeBSD. It should be possible to make it run on other processor types by replacing the translation table with one for your CPU (and changing the byte-order if necessary). See the comments in table.x86 for a description of the format.
The current version supports only X11 displays, and all the user interface code is contained in the file x11.c. This code provides two functions, InitDisplay() and UpdateDisplay(), which are called at startup and 60 times per second respectively. All data is passed through global variables. If you want to use a different display type, you should need only replace these two functions with ones which support your display.
- Files
emu.c - main() and startup code
dynrec.c - Dynamic recompiler
io.c - Input/output register interface
mapper.c - Memory mapper
x11.c - X11 display fb.c - Framebuffer/pixmap display
pixels.c - Pixmap drawing code
d6502.c - 6502 disassembler
x86.S - x86 assembler code interface
table.x86 - Translation table for dynamic recompiler
comptbl.c - Compiles table.x86
See the file BUGS for a list of known problems.