[50G] Question

[Claudio L.]

(03-25-2015 04:33 AM)Tim Wessman Wrote:  Well, I think "simulator" is murky here. It actually is a native application in all locations. For example, you have Chrome on OSX and Chrome on windows. Is one a simulator of the other? The underlying code is essentially identical if you look at the whole. True, there are some specific bits that are different to handle differences in the underlying OS that is running the application, but the core of the application is identical.

I think "simulator" is an appropriate term. I'd say:
Emulator = One hardware platform trying to mimic exactly the behavior of a different platform. The same binary (possibly for a different CPU) runs on the emulator, and may not be aware that is not running on the original hardware.
Simulator = The same high level code or very similar, but a different binary (recompiled) running natively on a different platform. The simulation part comes from additional native code not present in the original platform that tries to replicate or "simulate" the behavior of the other platform's hardware, not necessarily identical, but using at least a similar API.

In this regards, the Prime is a simulator, not a native application because it tries to simulate the same hardware screen, with the same fixed resolution, and also draws a keyboard simulating the keys of the hardware platform.
Chrome is a native portable application, runs on all platforms, not simulating the screen, or the keys, or anything, but taking what's available on each platform and using it.
The Prime would be a native application if you could for example make it fullscreen and it would take advantage of the bigger screen to show more pixels (scaling the fixed resolution screen doesn't count, it's still "simulating" the low-res screen).

Back to the 50g: ARM improvements were implemented as new opcodes in the emulated platform: First you have a 100% compatible emulation of the old hardware, then they added a few new "instructions" to the old processor to do things faster, and even to do direct code execution on the host platform, but all within the emulated platform.
So what you have is a new binary ROM that is slightly modified to run on the enhanced virtual Saturn, which has a few improvements over the physical chip but is still a completely emulated platform.

To answer the original question, on the PC, Android and iOS, you have Emu48 (and various others derivatives and rewrites), which is a Saturn emulator, running the hp49 original Saturn ROM with no enhancements.
At first, it appears logical to provide the same enhancements to the virtual Saturn in Emu48 as the 50g emulator has, then running the new enhanced ROM for faster response.
The problem with that is that one of the key enhancements was to allow running native ARM code (hpgcc used those extensions to run C programs). You can only use those extensions if you actually emulate the ARM processor too, otherwise programs using hpgcc wouldn't execute. So it would be faster, enhanced but crippled and not 100% identical to a real 50g.
That gave birth to x49gp, the only one I know of that is an ARM emulator capable of running the same ARM binary ROM that runs on the 50g, which in turn emulates the new "enhanced" virtual Saturn.

Claudio