N64 recompilation and amiga application

[copse]

I'd be interested in a thought experiment into the practicality of using this technique with Amiga related projects.

Existing emulators have used recompilation but were limited in how the recompiled version worked and differed from the original. This new tool allows how the game works to be modified so it can run natively, rather than as before on presumably an emulated display that is rendered natively.

Here is Digital Foundry showing different ways a recompiled project can be generated (anti-aliasing, ray tracing, original resolution, etc) and comparison between the outputs:

[ Show youtube player ]

Here is Modern Video Gamer showing himself going through the process and doing it for several games:

[ Show youtube player ]

[copse]

The process of recompilation is not automatic. Someone has to disassemble the code and:

1. Identify the entry point.
2. Functions.
3. External calls.

This is then used to produce C (c++ ?) code that is portable and can be compiled against a target API.

Now this is for N64 and the library calls are fixed and known and there is perhaps more of a mapping of it to the native target APIs we use today.

[lmimmfn]

What JOTD is doing with his arcade ports is similar except rather than converting Z80 instructions to C its transcoding directly to 68K instructions(JOTD can clarify ). Arcade ports are different from N64 though in that each arcade machine has different gfx/sound hardware and those need to be rewritten to map to Amiga hardware vs N64 where it is just one platform.

The N64 recompilation to C code & compiling natively is fine for modern hardware as CPUs/Gfx hardware has hugely improved since the days of the N64 so its not required to recompile to native assembly, i.e. the C step would be too slow on Amiga.

[gimbal]

Simple version: you need a monster PC to run a game which looks like a PC game from the 90's that ran fine on late 90's hardware

[copse]

Originally Posted by lmimmfn

What JOTD is doing with his arcade ports is similar except rather than converting Z80 instructions to C its transcoding directly to 68K instructions(JOTD can clarify ). Arcade ports are different from N64 though in that each arcade machine has different gfx/sound hardware and those need to be rewritten to map to Amiga hardware vs N64 where it is just one platform.

The N64 recompilation to C code & compiling natively is fine for modern hardware as CPUs/Gfx hardware has hugely improved since the days of the N64 so its not required to recompile to native assembly, i.e. the C step would be too slow on Amiga.

I think the focus on C is irrelevant. As I understand it, the framework that this recompilation is based on translates to assembly as well and the C or C++ is just a variation of this (I think MVG refers to this specifically). For this to happen it is likely there is an intermediate representation that can be translated to whatever platform's assembler you want. This would be a more general form of what JOTD does.

The more complicated part is the automatic mapping of hardware access. In the case of the linked external functions for the N64 these can likely be shimmed out as a layer. In the case of CPC, ZX, C64, Amiga, Atari ST, etc where hardware access is performed, this layer is internalised and merged into the translated code and is much harder to shim out.

If an Amiga or Atari ST instead uses OS calls then this can ideally be shimmed out. In fact, I would suspect that vamos could be extended in the same way.

Now, if we look back to the N64 recompilation we can see that there is an intermediate step where a coder needs to mark methods to guide the recompilation translation to C step. We can now think to paraj's efforts to shim out graphics methods for the flight simulator to speed it up by doing graphics operations in fast memory for instance. Of course there's a lot more work here and it's much harder for output platforms with direct hardware access.

[x-vision]

Originally Posted by gimbal

simple version: You need a monster pc to run a game which looks like a pc game from the 90's that ran fine on late 90's hardware

no.

[Cris1997XX]

Originally Posted by x-vision

no.

yes.