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EMU OS

Revamp branch contains WIP (booting, and loading and executing the kernel) code following the __stdcall calling convention

An operating system written from scratch to run the Chip8 apps and later, the NES apps.

It uses only x86 assembly language, and currently runs in 16 bit real mode only. However, the scratch folder contains working code to jump to 32 bit protected mode, setting up the VESA bios extensions, and setting up and drawing font glyphs to the screen.

It comes bundled with the test suite roms from here

Screenshots

  • Home Screen

Home Screen Screenshot

  • Chip8 Logo

Chip8 Logo Screenshot

  • IBM Logo

IBM Logo Screenshot

  • Corax+ Opcode Test.

As you can see, one test is failing.

Corax+ Screenshot

User Input

The home screen is displayed on boot. Arrow keys from the keyboard can be used to change the current selection. Pressing Enter on the keyboard executes the selected application. Once inside the application pressing Esc will bring you back to the home screen.

Build Info

Requirements

This was developed in the Windows Subsystem for Linux 2 environment

The required packages can be installed with

sudo apt install nasm gcc make bochs bochs-x bochsbios vgabios

You might also need to install libalsasound2.

If testing with qemu is desired please install the qemu-x86 package.

VcXsrv is required to display the GUI for the apps from WSL. Available from Sourceforge

Using bochs-sdl2 for the display only showed the graphics mode 'drawing' output but the initial teletype output would always be black. bochs-x displays all types of modes as expected. Also the application startup time reduced greatly with bochs-x compared to bochs-sdl2.

Making

make will

  • compile the assembly files in to freestanding binaries, using nasm.
  • compile the tools into OS binaries.
  • create a 15 MB blank disk image file in the build folder.
  • copy the boot binary into the image.
  • copy the kernel and the Chip8 roms to the disk image using emufs_copy.

make clean will

  • delete everything from the build folder.

make debug will

  • run the image through bochs emulator.

make run will

  • run the image through the qemu emulator.

Adding ROMs to disk image

build/emufs_copy <disk_image> <rom>

It will be added to the disk image and a table entry with be added to the table. It will show up in the main menu when the OS boots up.

The file table size is 512 bytes and each table entry is 14 bytes.