Hacking What's going on with saves?

MunkeeMan · Jul 21, 2006

Hey guys,

I was gonna buy a G6 Lite because I thought it wasn't like the EZ4 Lite...as in you don't have to restart your system in order to save your game to the cart. But recently I've seen that in the new G6 firmware that you have to do it the same way as EZ4 Lite.

Is this true?

Thanks

outphase · Jul 21, 2006

This can go either way as it might be the same as before or not, but if it does require a restart, the save is held in sram until you turn it back on. You don't need to soft reset to store the saves as it will take care of that automatically whenever you turn it off/on.

Lily · Jul 21, 2006

It's the same as before, it writes saves to the cart without any need of a restart.

outphase · Jul 21, 2006

QUOTE(Qrayzie @ Jul 21 2006 said:
It's the same as before, it writes saves to the cart without any need of a restart.

Kinda makes me wonder what goes on in the "do not turn off" time

pelago · Jul 21, 2006

It should be easy enough to prove what it's doing:

1, Load a game onto the G6 Lite
2, Play it a bit and save the game
3, Switch the DS off and on a few times, just to make sure the save is definitely on the cart
4, Put the G6L in your PC and copy the savegame (.0) file onto your PC
5, Put the G6L back into the DS
6, Play the same game some more and save it
7, Turn off the DS but do not turn it back on
8, Put the G6L back in your PC and copy the savegame (.0) file onto your PC, giving it a different filename
9, Binary compare the two savegames to see if they are different. (e.g. from a dos prompt fc /b save1.0 save2.0)

If the G6L writes directly to the savegame.0 file as soon as you save in-game, then the files will be different. If it doesn't actually write to the savegame.0 file until you next switch the DS/G6L off and on again, then the two files should still be the same.

VomitOnLino · Jul 21, 2006

QUOTE(pelago @ Jul 21 2006 said:
It should be easy enough to prove what it's doing:

1, Load a game onto the G6 Lite
2, Play it a bit and save the game
3, Switch the DS off and on a few times, just to make sure the save is definitely on the cart
4, Put the G6L in your PC and copy the savegame (.0) file onto your PC
5, Put the G6L back into the DS
6, Play the same game some more and save it
7, Turn off the DS but do not turn it back on
8, Put the G6L back in your PC and copy the savegame (.0) file onto your PC, giving it a different filename
9, Binary compare the two savegames to see if they are different. (e.g. from a dos prompt fc /b save1.0 save2.0)

If the G6L writes directly to the savegame.0 file as soon as you save in-game, then the files will be different. If it doesn't actually write to the savegame.0 file until you next switch the DS/G6L off and on again, then the two files should still be the same.

This sounds reasonable, and I will try it when I get the hands on my G6Ls which are currently underway.

Killermech · Jul 21, 2006

To be honest, it would make perfect sense to some past experience with saves I've had if this is true.. If it actually writes the save to the proper game save file when it's turned on from the sram.

Sometimes in the past, i've backuped the .0 save file just to find out that the save was a bit 'old' when used it back in the game. As in, it would restore an older save point than what I originally did. So I've always backuped the save to .1 and when backuping the saves. I copied over the .0 and .1 file to my hd just in case.

But if this whole theory is true, then as I said. It would make perfect sense in why I would experience an older savepoint than I had. As I might have not turned the game back on at that time and just copied the files over to the hd.

EDIT:This is just a theory atm, as im not home atm and uncapable of testing it myself.

But I think the whole 'save process' works like this:

You play a game and save. It then saves to sram and uses the gamesave.0 file in the ndsgame dir. A savefile non independent to any game.

When you turn on your nds, it 'copies' (or backups if you prefer) to the 'gamename.0'. file

ceevee · Jul 21, 2006

The G6 Lite does need a restart. This isn't a new thing either because the same things happened to me w/ 4.0beta, 4.0, 4.0a, 4.1, and 4.1a loaders. I have the Chinese G6 Lite.

Even before 4.1 came out & had that new 'data processing ... don't turn off the power!' disclaimer, the saves were not being written to the cart until a restart. Before 4.1, I played a game, saved something to a slot, then turned off the DS Lite. I immediately backed up that .0 save file to my computer using the U-disk burner w/o restarting the G6 Lite. I put the G6 Lite back in and played the same game. The changes to the save were recorded (because the G6 lite was restarted).

Then I put the .0 save file that I just put on my computer back on to the G6 Lite. There were NO changes to the save file; I didn't see my new save slot. This is because I didn't restart the G6 Lite before I put the .0 save file in my computer.

I also verified the CRC32 checksums to 2 save files in a method like pelago's & the checksums were the same. They should NOT be the same if the changes were made to the cart.

I guess they put that disclaimer on recently because people were losing saves, like I was. But the only thing you should be worried about is making sure that you restart the G6 Lite in your DS before backing up your saves. It only takes one restart.

And the required restart is apparent because the disclaimer only appears if you played a game the last time you turned on the G6 Lite. If you turn on the G6 Lite w/o playing a game, turned it off, then turned it back on, the disclaimer does not appear.

//edit: It really isn't a problem because you're bound to restart the G6 Lite to play another game. Just make sure you soft reset or turn on then off your DS w/ the G6 Lite in before you backup your saves.

gryto · Jul 21, 2006

It's not like you have to restart it as soon as you have finished... As long as the sram battery isn't flat you can just play, turn off and come back when ever you want. The process is quite transparent.

Lily · Jul 21, 2006

It's interesting that folks are experiencing this.

The most interesting test is to play multiple games without turning the DS off. (Using the hotkey combination to go back to the G6 Menu.) They all save fine, and the screen does not appear when the DS is turned on again.

gryto · Jul 21, 2006

I think it backs up the save when it resets.

SpaceJump · Jul 22, 2006

QUOTE(gryto @ Jul 21 2006 said:
I think it backs up the save when it resets.

Indeed. The M3 does the same upon soft-reset.

Dirtie · Jul 22, 2006

QUOTE(Qrayzie @ Jul 22 2006 said:
It's interesting that folks are experiencing this.

The most interesting test is to play multiple games without turning the DS off. (Using the hotkey combination to go back to the G6 Menu.) They all save fine, and the screen does not appear when the DS is turned on again.

The reason for this is probably because the save data is still in the SRAM (rather than a file), so it doesn't really prove anything. Pelago has the best idea.

Lily · Jul 22, 2006

QUOTE(Dirtie @ Jul 22 2006 said:
QUOTE(Qrayzie @ Jul 22 2006 said:

It's interesting that folks are experiencing this.

The most interesting test is to play multiple games without turning the DS off. (Using the hotkey combination to go back to the G6 Menu.) They all save fine, and the screen does not appear when the DS is turned on again.

The reason for this is probably because the save data is still in the SRAM (rather than a file), so it doesn't really prove anything. Pelago has the best idea.

Click to expand...

If it held the last save in SRAM, when I turn off/on the NDS, I should be presented with the same screen while the save is written according to the claims in this thread - but it does not do that.

Killermech · Jul 22, 2006

They have said that when you use the 'reset' feature to save, that it doesn't use the battery. So I doubt it uses the sram process when using that. It prob uses the gamesave.0 or gamename.0 directly for access and writing.

ceevee · Jul 22, 2006

If you soft reset after playing a game, then turn it off, the disclaimer should not show when the DS is turned back on.

If you turn it off while in the game, the disclaimer should show when turned back on.

pelago · Jul 22, 2006

ceevee and killermech's testing and experience has convinced me that the G6 does work the way I expected, that the save is kept in the G6L battery-backed SRAM and not actually written to the (non-battery-backed) cart filesystem until you soft-reset or turn the DS off and on again.

It's a bit of a shame it doesn't save immediately directly to the gamename.0 file in the filesystem, but I guess the technology isn't ready yet to support that. I'm just guessing, but maybe the type of memory that the DS is expecting to access for saves has to be of a fast type, and the normal cart filesystem memory isn't quick enough to be directly accessed by the DS, hence having to use faster SRAM.

Qrayzie is right that in normal usage of the DS and G6L this probably doesn't make much difference. You can play multiple games and turn the device off and on and the saves should 'just work'.

However, there are a couple of situations where you'll need to bear in mind that the save is actually initially kept in battery-backed SRAM. For example, people who only play the DS in short bursts, with a long gap between play sessions, may find that the G6L battery hasn't got a sufficient charge to keep the SRAM save protected until they next switch on. Such people, or anyone else worried about the battery, just need to make sure they soft-reset the DS after saving, or switch it off and quickly on again. The save is then 'permanently' written from battery-backed SRAM to the cart filesystem, which doesn't require a battery to keep alive.

The other time you need to bear the battery-backed SRAM save in mind is if you want to manipulate (e.g. backup or restore) your DS saves from a PC. Again you need to soft-reset or switch off and on the DS to properly write the DS to the cart filesystem, otherwise you won't be accessing the current save. (Obviously the actual save is stored somewhere on the cart, in the SRAM if this theory is correct, but I'm assuming that the SRAM is hidden and not accessible via the cart filesystem interface).

Some questions relevant to his theory - does anyone know:

1, How long the G6L battery will keep the save for, if the battery is fully charged? Is it hours, days, or weeks?
2, How long does it take for the G6L battery to charge?
3, Is the G6L battery charged while plugged into the DS or when plugged into the PC, or both?

Rykar · Jul 23, 2006

Does "turn on" mean simply turning the DS on or do you have to to access the G6 for it to save? And this soft reset do you mean the in game reset or is there a button combo to boot back to the G6 menu?

ceevee · Jul 23, 2006

'Turn on' means turning on the DS w/ the G6 Lite in it.

Soft reset means pressing L+R+X+Y+A+B to go back to the G6 menu while you're in game. Each rom needs to be patched w/ the soft reset option for this to be possible. It is not L+R+Start+Select, which resets some games to the main menu of the game.

Hacking What's going on with saves?

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