Monster is an all-in-one development system comprised of an editor, assembler, debugger, and linker all running natively on the Commodore Vic-20. The design philosophy is uncompromising maximalism without sacrificing efficiency or code density.

Large RAM expansions have become ubiquitous on the Vic-20 in recent years, so the philosophy of this project is to provide a rich feature set for a generously expanded memory configuration. Virtually any feature that I deem valuable in an assembly IDE is implemented. Monster leverages the Ultimem expansion to implement the following features (and many more) while running in such a way that almost the entire flat address space is still available for the user's program.

For more information about each of the major components of Monster, refer to the documents linked below.

Assembler

Editor

Debugger

Monitor

Linker

Monster requires the Ultimem to function.

Much of this RAM is used to store the multiple source code buffers (up to 8), but it is also used to store code, debug-info, and other data.

The banked memory allows the user program to execute in almost complete isolation. The user program state is entirely backed up in the Ultimem, which means that, although this environment consumes a vast amount of memory itself, everything except address the IO address space ($9800-$9fff) is preserved when control moves between the editor and the user program. Moreso even than small monitor cartridges, the program itself is virtually unaware of the resident tooling.

Prebuilt binaries can be found for all the necessary files in the bin/ directory. These can also be built from source with the Makefile. Build instructions can be found in the next section of this README.

To run from Disk find the BOOT.PRG and MASM.PRG files. Write these to your disk of choice and load Monster as you would any other program on your Vic-20:

LOAD "BOOT.PRG",8,1
RUN

The cartridge binary, monster.bin, can be flashed to your Ultimem to boot Monster directly from ROM.

If you wish to run Monster in an emulator (VICE), ensure that VICE is installed on your machine and run make start-disk or make start-cart from the root of the project to attach the corresponding disk or cartridge image. Alternatively, simply run VICE with the -ultimem argument:

xvic -ultimem monster.bin

• cc65 (tested with version 2.19)
• make
• python3 (any version should do)

The build process also requires python3 (any version should do).

Clone this repo git clone https://github.com/gummyworm/monster.git

cd to the directory you cloned to and run make for the appropriate target

Monster can be built for two targets: disk and cartridge. The disk format is useful if you want to test on your Ultimem without erasing its firmware.

The cartridge is a better choice for emulators or power users on real hardware. It loads significantly faster (although JiffyDOS mostly closes the gap between the two)

To build the disk version, run make TARGET=vic20 EXPANSION=ultimem disk

To build the cart version, run make TARGET=vic20 EXPANSION=ultimem cart

Here is a simple hello world program to demonstrate the basic syntax of the assembler:

.ORG $1400
START:
  JSR $E5B5
  LDX #$00
  LDA #' '
CLR:
  STA $1000,X
  STA $1100,X
  DEX
  BNE CLR
DISP:
  LDA MSG,X
  BEQ DONE
  JSR $FFD2
  INX
  BNE DISP
DONE:
  JMP DONE

MSG:
.DB "HELLO WORLD!",0