Y6502 is a 6502 simulator implemented in IBM/370 assembly language and FORTRAN IV on MUSIC. It was later ported to the VAX/VMS platform. The MUSIC version of the simulator is structured so that object modules can be added to it to implement features of specific 6502 based machines. Code is provided to implement a subset of the BBC Microcomputer. It may also be possible to write similar code to implement other machines such as the Commodore PET or Apple II for example. The BBC Micro operating system is not run natively but sufficient operating system entry points are provided by the simulation to enable language ROM images such as BBC Basic to run natively.
It is possible to read and write files in the MUSIC filesystem. Some keyboard input and most text based screen operations are possible, however, graphics operations, sound and other I/O methods are not provided for. Other than that, an environment similar to that in a 6502 second processor is provided. More 6502 memory is available for programs as less is required for OS functions but attempts to access hardware directly do not work, particularly attempts to access screen memory directly.
Its origins are in a Z80 simulator written in FORTRAN IV to run on MUSIC. See Z80 microprocessor simulator for MUSIC.
I later ported the code to VAX/VMS. See Y6502 BBC Micro / 6502 microprocessor simulator for VAX/VMS.
In writing this code, I initially didn't really believe it would ever work as a plausable BBC Micro simulation. Therefore, much of the code which implements BBC Micro functions is fairly awful hacks. I didn't wan't to put too much effort into doing a proper job of something I didn't think would succeed anyway, just to see how far along I could get. That's my excuse and I'm sticking to it :-)
A .het (Hercules emulated tape) image of the software is provided for those running the MUSIC/SP demo system on Hercules who would like to see the simulator running.
Y6502 simulator for MUSIC tape image.
Installation instructions are provided in install.txt.
Sim390 users probably can't use .het tape images but can download the required source files from:
Y6502 simulator for MUSIC source files.
and transfer them to MUSIC using FTP or some other method.
Once the files are in place, the simulator can be built by following the instructions in building.txt.
The original version of the simulator was written to be compiled by the IBM VS FORTRAN compiler. This was not at all compatible with the FORTRAN G compiler available for use with the MUSIC/SP demo system. Along with some manual alteration, a translation library provided with the WATFIV fortran compiler was used to translate the VS FORTRAN source to FORTRAN IV source which could be compiled by FORTRAN G. The original VS FORTRAN code is also supplied for reference.
After installation, give the MUSIC command
BBCto run the simulator.
Mail _software_@_beyondthepale_._ie_ (without the underscores) for further information.