Classic, a Guildhall tools applet

Classic is a Tools applet that emulates a Motorola 68K processor and tries to emulate the A-line traps used by applications that once ran on Mac's System 9. Unlike existing emulators for that system it will attempt to effect the emulation without requiring or emulating any Apple ROM code. This is not going to be a simple task. The 68K part of the emulator was clearly the easy part. As shown below it's pretty far along. Duplicating the functionality of those A-line traps will be difficult. But it's also true that most of what's needed to get the old applications to run is already present in Guildhall's internal toolbox. So it's not hopeless. Just really, really hard.

Another curiosity I have about this emulator isn't centered on System 9 at all. With the 68K virtual machine already pretty functional (from scratch, because it was fun), I got to wondering about using it as an alternate pseudo code for Codex compilations. The trick is, though, the current 68K virtual machine won't work. The number system assumed by Codex includes 64 bit integers and 128 bit floating point numbers. So I've begun to think about what a 64 bit 68K architecture would be like. There are few discussions on that topic out on the web, if I recall correctly proposing a 68080 instruction set. I didn't find a good spec for that, or mention of any compilers for it, but there are open source versions of true 68K compilers out there that perhaps could be adapted.

Next Steps

This applet is on a back burner, but as ideas spring forward regarding a 68080 instruction set I'll jot them down and see where they lead.