M68K for DC

[Ian_micheal]

[quote author=Propeller link=board=dcemu;num=1083323639;start=30#38 date=05/06/04 at 09:15:14]Anyway guys, emulating the Amiga 500 is not the only point on this idea. An asm done 68k core for the sh4 would undoubtely improve things. If it's possible to emulate Amiga, we'll do it, but it's not the only point I see on this proposal. There's a lot of fun hidden in here, and everyone is called to collaborate. And don't set the Amiga emulation as the only goal, because I think that the next step in dcemulation will be doing fast mean and sharp asm cores, starting from the most commonly used ones, and this means m68K.

I also appreciate Ian's interest on this subject: Undoubtely, there's not an *easy* or *fast* way to emulate Amiga, but we may keep searching for a way to achieve a good compatibility combined with fast (but not complete) hardware emulation.

Thanks for all of your replies, I'm so happy that this topic suggested a hot, interesting discussion.

Propeller[/quote]

There is no way to do an amiga emulator with out complete emulation thats the catch. Every game uses every part of the hardware. DMA system is very complex. I think some of you should look at sh3 asm it runs on dreamcast and is more compact And runs slight faster. But The sh4 core's your talking about asm Have to be API complaint or were going to have to Totaly re do any emulators to match it leading to a lot of work.

I love to see MUSASHI Version 3.3 Re written in sh3 or sh4. API complaint. over night lots of project fullspeed or close to it neogeocd mame projects genesis plus many more use this core.

But sh4 asm is not going to help if the cpu is running fullspeed in c example snes emulation. SH4 and asm is not the god cure to hardware limts of the dreamcast.

Im only a c coder and porter. I know your main goal should not be the amiga. It's a waste of good time that could be spent doing some thing that can be achived.

Debate is fine but none understading of the machine your wanting to emulate and the dreamcast limts is going to end with a whole lot of people upset.


Atari st and mac plus sound good. Good luck to you guys but these new cores would have to be API complaint with c cores we used to be of a lot of use. Moding emulators back and forth to match the cpu cores is not allways easy or a nice thing to do can break things working.


Any way motvation needs to spring from some thing that can be achived and worked for.

Good luck guys ill leave it at that.

[Propeller]

Yeah, compatibility is not an option at this time, Ian. It *must* be compatible with the most often used core.

And about that problem you refer to, the cpu running fullspeed in C... if there are spare cycles on a CPU, one must use them. Maybe implementing multitasking, maybe doing another type of emulation (there are more than one or two type...) but that's a "must be".

Propeller

[Ian_micheal]

Must often used core is MUSASHI m68k. Used in almost every project on dc that uses a m68k. I think some optimzing tips from some of, you guys, would be handy. For these cores. Snes9x uses a tight loop checking functions and varys it depending on load as far as i understand it's turned on via a -D which works and brings 10% speed. type of vary-able unclocking depending on load or left over cpu cycles.

If thats what your talking about. There is Nothing much but setup and porting and compiler settings i can help with and basic c coding. ASM is not my strong point i leave that to the compiler. Sorting out the compiler to make better code for all of us, would help as well. Unless your an sh4 expert gcc is going to make code almost as fast as badly made hand tuned asm.

I lend any help i can on it. Mostly will be porting and setup. Asm is some thing i dont have the skill for at this time. Gcc compiler would beat me.

[Stef]

[quote author=Ian_micheal link=board=dcemu;num=1083323639;start=30#40 date=05/06/04 at 12:39:35]
I think some of you should look at sh3 asm it runs on dreamcast and is more compact And runs slight faster.
[/quote]

What are you talking about ???
Do you mean there is a M68000 CPU emulator written in SH3 assembly ?

But sh4 asm is not going to help if the cpu is running fullspeed in c *example snes emulation. SH4 and asm is not the god cure to hardware limts of the dreamcast.

I guess we can emulate a 16 Mhz 68000 with Musashi on a DC, nice, this is actually twine as much we need for Genesis for instance, for that means it still take about 50% of CPU time just for the 68K emulation !
Then only half of CPU power is available to emulate the rest ... it's always better to have a faster core, then you have more time for the rest.
Of course, optimise the 68K core only isn't really usefull, i know Genesis Plus won't be fullspeed just by changing musashi, even without 68000 emulation, Genesis Plus DC doesn't run at full speed :-/

[Propeller]

Thanks for your support, Ian. By the way, I knew Musashi is the most often used C core for 68k, but it was just a way for me to refer to it, calling it "the most used" ;D

Now, it's time for documentation, after MadriDC (we're kinda overloaded for now) we'll start.

Propeller

[Ian_micheal]

[quote author=Stef link=board=dcemu;num=1083323639;start=30#43 date=05/06/04 at 15:34:22]

What are you talking about ???
Do you mean there is a M68000 CPU emulator written in SH3 assembly ?


No i wish . Sh3 asm runs on the dreamcast it can run sh3 code sh4 chip is compatable with sh3 code. On some tests ive seen on docs sh3 runs faster then sh4 asm on the sh4 chip some times not allways. But it's intresting.

SH4 chip in the dreamcast can run sh3 code compiled for it.

Dont hold me to it. But Gleem used a sh2 asm core in the nes emu for example. So we could use sh2 or sh3 asm on the dreamcast that might give a wider range of coders a chance.

Gleem the first nes emu used a sh2 cpu core.

[Christuserloeser]

The DreamSNES team rewrote the 65c816 SNES CPU (clocked at 3,58Mhz) specific code only to SH4 assembler to get faster emulation results and IMO it really shows: After porting and further optimizations, emulation speed has almost doubled! Main prob with SNES were gfx and sound!

If M68k SH4 would take the CPU time under the 50% mark even SegaCD and AMIGA500 emulation could be possible!

[quote author=Ian_micheal link=board=dcemu;num=1083323639;start=30#36 date=05/06/04 at 05:02:21]Why dont we work on nogeo cd it's near perfect and only needs a little push from other people i cant seem to fix cd audio on all games or get sfx to work right. It's open source. If were working for the greater good then it's a good project. Many others that need finshing like *wonderswan all of use working on it would be finshed.[/quote]

I thought u`d just take a break! I didnt know u were getting stucked with this! I`d like to help out since I realy love the NeoCD for DC but I can`t program :-[
Damn, look how much ppl are getting back to the scene after this great release! Its the currently most important project for the DC scene!


Chris

[Clessy]

If you cant go anywhere with speed on NeoGeo Cd emulation you can defanitly go much father in options and menu's.

Also I'm still trying to figure out why you never finshed WonderSwan Emulation. It need's saving and sound and Oswan for PC has really nice sound now too. Nothing compared to Wscamp still but its much better than it use to be.

[quzar]

that thing is hard. i tried to do things to the source, but ian has lost his old source anyways so anything would have to be a from scratch fix

[Ian_micheal]

Ok Maybe this is easyer .

3mhz cpu emulated on the super SH4 chip runs fullspeed Making it Converting it to SH4 would have little to no effect *when the emulated chip is running fullspeed.


Amiga is impossable to do on the dreamcast at any useable speed.