Emulators with rewind option


Seb

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Joined
Aug 25, 2003
Messages
53
I really don't know how you guys feel with "rewind".


I'm a full time teacher with a 2yo boy so i can't find a lot of time to play.


I used to have a psp and i was happy to have a "rewind" option like in nesterj, so i was able to play and finish the first zelda without spending to much time. I do know that it is not the same as finishing the game the normal way but at least i was able to finish it.


So what about a "rewind" option in emulators ?
 
It's more complicated than you probably think. Even a simple console like the NES would be very complex to imlement - You'd need a running log of memory accesses and register/port changes for every instruction the CPU executes, which would either fill memory very rapidly or write huge amounts to disk over time.


The only other way to implement it would be to save "snapshots" of the machine's internal state every few seconds or so - which again would be fine for a small, low-memory unit like the SNES but when you get into the realms of PSX or N64 you're looking at multiple megs of data being written every time. It's not practical for more advanced emulations.


D.
 
I don't say it is easy because I really don't have a clue how to do it, i'm not into coding.


Just thinking about me and myself and an easy way to play games.


A psp could do it so I was thinking that, probably, a pandora could do it too but you're right as I didn't know how to do it and maybe speaking about systems isn't relevant at all.
 
I don't understand whats different about a rewind that a simple mapped keyboard shortcut of a save state won't do.


I mean it would be nice to be able to rewind but if you are paranoid you can hit the save state all the time :D
 
Actual rewind is probably too much effort, and might not be feasible at all. But I imagine it should be reasonably easy to modify any emulator to automatically save its state every 10 seconds, and keep track of the last few saves. That's probably all you need. It should be doable without too much performance overhead (perhaps increase those 10 seconds to some slightly bigger number for PSX/N64, and perhaps you'll get a few framedrops while it is copying the state to some other area in memory; if you're tight on memory it'll also need to write the states to disk (SD), but it can do that slowly in the background).


You can also just play the game and save a lot, that's what I usually do. The advantage of that approach is that you can save just before some important decision, and don't overwrite that save slot until you're certain that it was the right one.
 
that's what i do, hit the save state.


Just that rewind is more " in the game" , you stay in your game, rewind and just turn right to avoid being hit, but you're right, save state are great too.
 
Here's the source code for SMS plus with rewind feature:


http://svn.akop.org/...smsplus/1.2.55/


Save states are nice, but it's a really cool feature to rewind the gameplay at any time. I have used the nes emulator with rewind, it is very fluid and doesn't pull you out of the game as much as if you were hitting save state every so often.
 
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