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NES emulation

vbt - Feb 2, 2003

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ExCyber

Nov 6, 2003

	
	
		
		
			That'd probably be insanely hard, if it was possible at all.

Aside from DMA timing (which I imagine would be a tremendous pain in the ass), is there anything else that would be a really tough issue?

slinga

Nov 7, 2003

	
	
		
		
			Originally posted by Tagrineth@Nov 6, 2003 @ 11:02 PM



 vbt, here's a thought... try to get multiprocessing running on the 68k (say, run the sound on it) before using the second SH-2, and see how that runs.

I don't follow. By 68k do you mean the saturn's sound processor (which is similiar to the genesis cpu)? And if so, do you mean to emulate all of the NES sound system on that cpu? :huh

		AntiPasta		Nov 7, 2003
			Hey, the entire Speccy has been emulated on a 68k In fact I think it's a pretty neat idea, but not that neat that it can replace one of the SH2's... that is, if you can find a useful use for dual CPUs in a emulator.

Tagrineth

Nov 7, 2003

	
	
		
		
			Originally posted by slinga@Nov 7, 2003 @ 11:56 AM



 I don't follow. By 68k do you mean the saturn's sound processor (which is similiar to the genesis cpu)? And if so, do you mean to emulate all of the NES sound system on that cpu? :huh

Yes, I mean the Motorola 68EC000 that controls the sound chip in Saturn.

	
	
		
		
			Hey, the entire Speccy has been emulated on a 68k



In fact I think it's a pretty neat idea, but not that neat that it can replace one of the SH2's... that is, if you can find a useful use for dual CPUs in a emulator.

See, 68k is surprisingly powerful and NES's sound... isn't.

Hell, Pagefault (of ZSNES fame) said it might be possible to run the SNES's famous SPC700 entirely on that 68k. And yes, he's done some Saturn work now.

And dual CPU's are insanely useful in emulation. More spread out processing resources = very good for emulation, since you're emulating several chips at once. Context switches aren't exactly good for performance.

And... I know it can't replace one of the SH-2's, BUT it's a lot easier according to pf to get "MP" running via the 68k and one SH-2 than via both SH-2's, and this could be all vbt needs to get speed up. It was just a suggestion to do first, since it's a good idea anyway, and if necessary he can still spread work onto the other SH-2... but they aren't called Twin Terrors for no reason.

		antime		Nov 7, 2003
			Mehh, what OS are you running to suffer from context switching penalties?

		Jurai		Nov 7, 2003
			does this require a comms card?

Tagrineth

Nov 7, 2003

	
	
		
		
			Originally posted by antime@Nov 7, 2003 @ 04:48 PM



 Mehh, what OS are you running to suffer from context switching penalties?

It's a given. Nothing to do with OS, it's part of CPU architecture.

I'd like to see you develop a CPU which can flush its pipeline and L1 cache, redirect pointers, and refill its pipeline in one cycle.

		slinga		Nov 7, 2003
			I'm with Antime on this one. CSPs only occur when you swap in\out processes\threads. I'd assume that VBT's code would be multithreaded (how else would you make use of the dual cpus?), but that each thread would run on its CPU. So 2 threads on 2 cpus = no switching processes.

antime

Nov 7, 2003

	
	
		
		
			Originally posted by Tagrineth@Nov 8, 2003 @ 01:34 AM



 I'd like to see you develop a CPU which can flush its pipeline and L1 cache, redirect pointers, and refill its pipeline in one cycle.

But why would you do any of that? (And if you really want to know, there are CPUs which do zero-cycle context switches by storing the needed data on-chip. Obviously it only works for a set number of processes.)

Tagrineth

Nov 7, 2003

	
	
		
		
			Originally posted by antime+Nov 7, 2003 @ 06:19 PM-->QUOTE(antime @ Nov 7, 2003 @ 06:19 PM)