A hobby project that replicates the 6502js emulator, but with the speed of C. Why? For fun and learning :D
- Simple on the outside: Replicates the simple and educational 6502js environment.
- Simple on the inside: Plain C, and almost no libraries, not even SDL2.
- Fast: Runs up to 37Mhz on my machine. In comparison, 6502js (and the accompanying demos) run at around 30Khz.
- Correct: Passes Klaus functional tests, and Bruce Clark's decimal mode tests.
For programmers, the OS layer contains an example on how to use X11, Cocoa/Quartz2D or Win32 to draw stuff without a library like SDL2. See for programmers for more info.
This emulator does not have a built-in assembler. Check out writing your own binaries for a recommended third-party assembler. Alternatively, check out 6502asm or easy6502.
Finally, do note that this emulator does not have accurate cycle emulation (1 instruction = 1 cycle).
Download binaries for Windows or Mac on the releases page.
For Linux, please compile from source.
Downloads come with a folder of demo binaries which you can use to try out the emulator with. If you wish to write your own, please see writing your own binaries.
For Windows and Mac, simply run by double-clicking the app. However, if you want to change the speed, you'll need to run via command line. The default speed is 30Khz, which is appropriate for most demos.
Command line options:
Usage: 6502 file.bin [options]
Options:
-unlimited: Run with no speed limiter (default: limited)
-s(speed_in_khz): Set speed limit (default: 30)
For Linux, you'll need to run via command line.
Use any assembler for this that can produce simple binaries. I would recommend Virtual 6502 Assembler.
The emulator will load your code into $0600. Specify this in your assembler by putting in *=$600 or similar.
The screen is from memory address $0200 to $05FF, from the top-left to the bottom-right corner for a total of 32 x 32 pixels. Colours repeat after $F. Colour list:
$0 Black
$1 White
$2 Red
$3 Cyan
$4 Purple
$5 Green
$6 Blue
$7 Yellow
$8 Orange
$9 Brown
$A Light Red
$B Dark Gray
$C Gray
$D Light Green
$E Light Blue
$F Light Gray
To get user input, read from $FF, which will be changed to the ASCII value of the character pressed, when the user presses a keyboard button.
To get a random number, read from $FE, which will change every cycle.
Please check main.c for a bunch of fun configuration options, such as the ability to change memory locations, the screen size, FPS, and various debug utilities.
You'll need MingW. (Not tested on actual Windows, I cross-compile via Mac instead.)
Edit build-windows-mingw.sh to change CC to your compiler and LIBRARIES to point to the MingW versions of libcomdlg32 and libgdi32. Compile by running sh build-windows-mingw.sh.
You'll need XCode. Compile by running sh build-mac.sh, or just compile mac6502 from XCode.
You may try compiling without XCode. Just make sure to compile both main.c and mac.c and include -framework Cocoa. However, you will only get a Unix binary, and the menu bar may not work properly.
You'll need XCB and XKBCommon. Edit build-linux.sh to point to your installation of XCB and XKBCommon. Compile by running sh build-linux.sh.
main.ccontains all of the emulator code.os.hcontains a common interface for all 3 OSes, inspired by SDL2.windows.c,linux.c, andmac6502/mac6502/mac.mcontain working examples of how to create a window, receive user input and draw rects using Win32, X11 (via XCB/XKBCommon) and Cocoa/Quartz2D.
It's not the best code (I'm still learning), and it's not hardware accelerated, but some of this information was hard to find, so I hope my code can help you here too.
Merge requests are welcome! Issues are too, but this is just a hobby project for me, so please be patient.