An Oberon System for the VM-8 computer, and a Linux emulator
This is the third version of a system for the VM-8 Computer : now it is written in Oberon-07 only, and the Turbo Modula-2 Reloaded compiler is not supported any more...
Short rationale for the abandon of Turbo Modula-2 :
- firstly, the Turbo Modula-2 compiler actually required more than 64 KB (in order to run in the 64 KB address space, it used overlays, ie. the code of several modules shared the same location, these modules were loaded from disk each time a call or return required them to be present in memory),
- secondly, I have been experimenting working with a small stack (1 KB typically), it cannot work with the Turbo Modula-2 compiler (due to some recursions in the linked-lists of the symbol table), whilst it can work with the Oberon compiler,
- and thirdly, I gave up providing a proper decompiled source of Turbo Modula-2 (because the use of variant records makes the decompiling process such a hard puzzle to decipher).
The Oberon-07 compiler is derived from Project Oberon (http://www.projectoberon.com/) : roughly, it replaces the custom-RISC code generator with a new code generator that targets a modified Turbo Modula-2 Reloaded VM (some opcodes are modified, and some other opcodes have been added).
The firmware for the VM-8 computer (ie. the Modified Turbo Modula-2 Virtual Machine) is provided on the MCodeOnAVR repository.
Alternatively, the system can be run on Linux-type systems, with the provided (ugly) VM implementation for Linux.
TODO: I need to provide a reduced FAT32 image of the SD card (due to the huge number of file operations I have done on this card, even if the size of the stored files is not so big, the compressed image of the 8 GB SDcard is too big for Github).
STATUS: The system is up and running, it is able to compile itself and can be modified. However, this is not the final released version yet, I intend to optimize the set of opcodes used in the VM. But for these experiments on the VM opcodes, it might be faster to have a cross-compiler in order to generate the VM and the system at the same time (this type of modification is currently very cumbersome to do on the target platform itself)... So, I'm currently developing an Oberon compiler targetting LLVM's Intermediate Representation.