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NullDC-360 project is back again

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#1 Xbox-Scene


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Posted 02 September 2012 - 03:29 PM

NullDC-360 project is back again
Posted by GaryOPA | September 2 10:29 EST | News Category: Xbox360
Dreamcast on 360

The DreamCast emulator for Xbox 360 emulator development has been resumed


Good news for all the retro-fans out there. One of the best Dreamcast emulators for PC, nullDC has been ported to Xbox 360 and after a long time stucked in development, it has been resumed. According to French developer GliGli:

Hey, as you might have noticed, I resumed my work on nulldc-360 and libxenon not long ago.

Iím currently working on 3 things: compatibility/sound/speed.

6 months ago I was badly stuck on 2 bugs, one texture endianess problem, and one random crash/infinite loop in the dynarec.
First thing I did was to look at that texture bug, in a few days I found the exact case where it happened and fixed it for good.
Then I fixed the dynarec one, it was quite an awful one: I forgot to save/restore the SH4 condition flag on dreamcast interruptions, so it was randomly corrupted as the emulated console handled its IRQs!
I fixed a few more bugs until it was clear I needed proper sound emulation for more games to boot.

Adding sound was relatively straightforward, of course there were the usual endianess related bugs, but I guess Iím getting used to it ^^
The Dreamcast sound chip (AICA) is a complex design, it has an ARM processor core, a 64 channel sound generator, and a DSP.
I donít emulate the DSP for now, many games donít really need it.
Main problem with sound is the induced emulator slowness, though thanks to the 360 multicore cpu, I was able to make it almost free.

Updating peripherals in the dynarec works that way: each code block knows how many SH4 cpu cycles it emulates, and each time a fixed number of cycles (448) is reached, it calls a procedure that updates those peripherals.
To multithread sound, and by the way, other peripherals, I run parts of that update on a separate core.
It runs concurently with the dynarec, and, basically, every 448 SH4 cycles both get sychronized. so as long as peripherals emulation takes less time than SH4 emulation, the dynarec doesnít have to wait for them!
So that makes them almost free to emulate, almost because they still stress the 360 L2 cache and memory controller a little.

Anyway, compatibility seems pretty good now, sound works, speed is more or less the same it was before sound emulation, a proper binary release *might* not be that far

News-Source: NullDC-360 project (via) 360 Crunch



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Posted 02 September 2012 - 11:14 PM

Sweet, JGR on the 360 before the XBLA port!

Great work keep it up

#3 ploggy


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Posted 03 September 2012 - 12:45 AM

Agreed. It would be hilarious if this was released and played Sonic Adventure 2 and JGR played at Fullspeed before the XBLA versions were released. smile.gif

#4 DaBuisneZ


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Posted 03 September 2012 - 03:28 PM

Awesome news. Powerstone here we come!!!

#5 -x-


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Posted 04 September 2012 - 05:12 AM

This is awesome. Great work!!!!

#6 justathief


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Posted 05 September 2012 - 10:34 PM

I cannot for the life of me understand how they could fail so miserably as they did with the Dreamcast...

I still remember buying it, and being completly blown away of how great Soul Calibur was!

It was just like having the real cabinet at home, such a huge step up from the other consoles...

Anyways, this is great news, going to put a 360 (w. a SSD) in my car later on, so emulators are great when having to kill a few minutes waiting for the missus to finish shopping...

#7 cablematrix


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Posted 08 September 2012 - 09:30 PM

So ready for this!
DC 4 Ever!

#8 Gromber


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Posted 10 September 2012 - 07:40 PM

It uses libxenon nor xexdk, must move to:


#9 garyopa


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Posted 10 September 2012 - 08:22 PM

QUOTE(Gromber @ Sep 10 2012, 02:40 PM) View Post

It uses libxenon nor xexdk, must move to:


Thanks this topic has now been moved.

I think we should really have an 'emulator' sub-forum now for 360, since there been so much development in that area recently, like we have for the original Xbox 1 forums, it would be much easier to find all the retro stuff in one place.

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