The purpose of this blog is documenting the development of the extension of the E-UAE Amiga emulator with the possibility of making use of Just-In-Time compile based Motorola 680x0 processor emulation.
A short lesson of history
WinUAE, the Amiga emulator for Windows have JIT compiling for many years now. Unfortunately, it is closely tied to the intel x86 architecture, because the most efficient way of implementing the JIT compiling is kinda similar to an actual programming language compiler: the end result is machine code, which is executed directly. Although it is possible to implement a processor independent JIT compiler, but to squeeze more speed from the executed code in a general compiling model is much more complex.
Recent Amiga (like) computers are using PowerPC processors, porting the WinUAE solution to PPC processor would be closely as hard to do as implementing a brand new solution. Not to mention that there are special requirements from the environment of the emulation, that cannot be simply resolved.
Since not many coders have experience with JIT compiling on the whole world, the line of applicants for creating JIT compiling for PowerPC processor was pretty short for years.
On the other side, users needed the JIT compiling for UAE emulation for running all sorts of the legacy applications, which cannot be run on the recent incarnation of the AmigaOS systems (because those are buggy, not system-friendly, hitting the hardware directly, and a number of other reasons). The demand was so high that even a bounty was set up for this specific project on the AmigaBounty site, yet nobody wanted to take the job.
The insane with a rattle
You might ask why anybody would invest countless hours into this project. And I must say it is a valid question.
I have already experience in this field, I completed the similar component in AmigaOS4 (code name: Petunia). If you are interested in the fine details of the JIT compiling, then I suggest checking out my Project Petunia web page.
There are a few other reasons; some folks were bugging me with it for years and it is a bit of a challenge. Also there is this typical feeling in every coder’s head, when a project finished: trying to implement it second time the outcome would be much better because of the previous experience.
Well, here is the time to see how well it goes…
Principles to follow
There are some ground rules I will try to keep to make as many future users happy as possible. These are:
- The source files will be freely available to anybody under GPL license or directly from me with a different license on request.
- While the development will be done on AmigaOS4, I won’t use any AmigaOS4-related feature, which makes it harder to port the solution to any platform. (It means my previous project won’t be used directly in any form.)
- I will try to keep the solution as flexible as possible, to let others make use of it without E-UAE.
- I won’t sacrifice compatibility over speed.
- I will implement some possible adjustments to let the user fine-tune the JIT and therefore improve compatibility with the old applications.
That is all for today, more technical details will follow in the next post.