M68K for DC

[BlackAura]

[quote author=fox68k link=board=dcemu;num=1083323639;start=300#308 date=08/03/04 at 17:01:49]Ian, what do you mean by advanced functions? built-in memory handling support?[/quote]

It needs to be able to trap BIOS calls for the CD emulation to work. It doesn't actually emulate the CD drive itself, but it intercepts the BIOS calls to access the CD, and emulates them using native file operations.

[Hola]

Is that why the cd audio is about 5 seconds delayed?

[BlackAura]

I don't think so. That's probably related to something else entirely.

[quzar]

Audio problems in NeoCD mostly stem from the fact that the CD audio drivers used the Z80 to do some stuff(not processing, but like really basic things) and the z80 is turned off and broken.

[fox68k]

[quote author=BlackAura link=board=dcemu;num=1083323639;start=300#310 date=08/03/04 at 19:44:57]

It needs to be able to trap BIOS calls for the CD emulation to work. It doesn't actually emulate the CD drive itself, but it intercepts the BIOS calls to access the CD, and emulates them using native file operations.[/quote]

I am going to try to guess what you mean:

NGCD emu changes interrupt handler routine (BIOS) to point to a new one to avoid CD access. Instead, NGCD emu emulates those accesses doing native file operations like you said, but those accesses are performed out of the m68k core, right? So this way, m68k core remains the same. I saw some code in NGCD emu that changes data directly before emulation process start probably getting things up about CD acceses. Right again?

Thanks.

[BlackAura]

Pretty much, yeah. When an interrupt is called, the emulator calls some native code which does the same thing instead of jumping to the appropriate M68k interrupt handler. The actual file I/O is performed outside the CPU core, of course, but there needs to be some mechanism to supply a callback function that can be used instead of calling an interrupt handler.

[fox68k]

[quote author=Hola link=board=dcemu;num=1083323639;start=300#309 date=08/03/04 at 17:41:13]Is there a estimated release date plained for this sh4 68000?
[/quote]

Not yet. There is work to do and i don't know when i could release it. I will keep you informed about progress.

[fox68k]

Very interesting BlackAura. I'd never thought about that feature :

How could i implement that in the core in a cool fashion? (i mean function interface or any other kind of management).

Thanks!

[BlackAura]

I've never seen any CPU emulator that implements that cleanly. The ones that implement this kind of feature at all tend to be fairly tightly integrated with the system emulator.

[Stef]

The way is done in musashi and C68K is just to wrap some undefined opcodes 0xFxxx to internals emulators functions.
Quite simple to do but it's a hack...