68K Access Under OS4

[nyteschayde]

Is it possible to access the 68K processor from OS4 just like we were once able to access the PPC from OS3.x? Basically RunInUAE is a great idea but is more or less completely unusable under OS4 Classic (at least with my BlizPPC).

It kills me I have a 68060 sitting there dreaming while the 603e struggles to emulate a 68K for E-UAE. Any chance of passing through to the real 68K (ala ShapeShifter for MacOS, etc...)

[nyteschayde]

OS4.1 is really quite nice. One very nice thing about RunInUAE is that it allows me to use the RTG graphics card for running classic OS games (in theory).

My reference to Shapeshifter was the direct use of the CPU in the emulated environment. This direct CPU usage was the only thing that allows Amigas to emulate 68K Macs at almost as fast, and sometimes faster, speeds as compared to a real one.

I've heard from the author/supporter of RunInUAE Christopher Handley that one of the main reasons RunInUAE is so slow is that there isn't a JIT being used in the emulation.

Anyhow, it doesn't look like this has been done or that people have tried to do it (access the 68k from OS4). Just thought I'd ask is all.

[nyteschayde]

See this thread: http://www.amigans.net/modules/xforum/viewtopic.php?topic_id=1296&forum=3&post_id=15422

Steve

That helps but simply raises more questions. E-UAE under OS4.1 doesn't have a JIT. Petunia is a perfectly working JIT but lacks the environment provided by E-UAE in order to make older games function correctly.

Has anybody done any dev work on OS4 that takes advantage of or directly works with Petunia? Do we know if there are APIs of any type exposed to allow this happen?

I've sent an email to Chris and Álmos about just this. If people want to chat more about it, feel free to do so; otherwise I'll update this thread later when/if I hear more from them.

[nyteschayde]

So Karlos, have you worked with the 68K or even accessed it at all from OS4? I know you have a lot of experience working with the PPC from 68K code but was curious if you've done anything from OS4 regarding the 68K?

[nyteschayde]

I'll forward that link to Chris and Álmos

UPDATE: I'm a dork. If I actually read closely I would have found the link to http://euaejit.blogspot.com/. On this page, the author of Petunia, Álmos is already working and likely nearing completion a JIT for E-UAE for OS4.1.

Still it would be nice to know more about this stuff being a dev myself who is getting into Amiga programming.

[nyteschayde]

Sure, I understand you're busy. I'm so fragmented with my time as well I never seem to get anything done. Just was curious on your level of experience with the OS4->68K usage as opposed to your past experiences.

[nyteschayde]

It might be possible but there are a few things you may need to consider.

Shapeshifter is not emulating the MAC's video hardware in the same sense that UAE emulates the every detail of the Amiga's chipset. Apple has an abstraction layer on the hardware (QuickDraw) and Shapeshifter patches into that.

The slowness with UAE may not even be the CPU emulation anyway. The bottleneck is far more likely emulating the custom chipset.

Finally, the architecture of UAE. For example the custom chip emulation may require hooks into the CPU emulation.

That may be, but other than the amount of work it would take to tap into the existing chips (and I understand there may be work there that is not easy; i.e. securing direct access to the chipset if that's even possible), all those custom chips are actually available and shouldn't need emulating. It's likely that the E-UAE Amiga port simply did the least amount of work as possible and avoided using the real hardware even though it does exist and is within easy reach.

Emulating an Amiga on an Amiga should be a fast process.