DSP-2 loadstate bug

[19day]

I did try searching for this bug, and only found one reference to it as an aside, dated quite some time ago: http://board.zsnes.com/phpBB2/viewtopic.php?t=244


The problem game is Dungeon Master, here's the NSRT readout:

Code: Select all

NSRT v3.3 RC2 - Nach's SNES ROM Tools

---------------------Internal ROM Info----------------------
       File: Dungeon Master (U).smc
       Name: DUNGEON MASTER         Company: LucasArts
     Header: SWC                       Bank: LoROM
Interleaved: No                        SRAM: 256 Kb
       Type: DSP-2 + Batt               ROM: 8 Mb
    Country: USA                      Video: NTSC
  ROM Speed: 200ns (SlowROM)       Revision: 1.0
   Checksum: Good 0x8724              CRC32: 0DFD9CEB
--------------------------Database--------------------------
   Name: Dungeon Master
Country: USA                    Revision: 1.0
 Port 1: Gamepad                  Port 2: Gamepad
Genre 1: First Person RPG        Genre 2: None

With both the 1.42 release, and trying the 0519 WIP, it seems the loadstate (or the save state and not being apparent until the state is loaded) screws something up, apparently with the DSP-2 emulation. To recreate, I just run the WIP version, load Dungeon Master, quickly enter the first screen of the dungeon, and then save and load state a couple of times, and quickly enough the dungeon view will vanish, reminding me of when DSP-2 wasn't emulated, since the display would work except the dungeon view, leading me to suspect that something goes wonky with the DSP emulation with the state saving/loading (and based on no further information, heh)

Hopefully I've covered everything I needed to from the bug-posting requirements. Oh, I would also like zsnes ported to my timex wristwatch

[Overload]

This is expected, if you did the same on a copier you would get the same result. Use the game to save, forget about savestates.

[Noxious Ninja]

Interesting. Why does that happen with state saves?

[Overload]

The dsp-2 is a coprocessor. You would need to save specific data if you wanted to restore it to the position it was when the state was captured.

Personally i don't see a point in saving this data because the game can be saved at anytime anyway and only one game uses the dsp-2.

It would be different if the upd77c25 chip was being emulated but i doubt that will ever happen.

[grinvader]

Well, since we already store extra chip status in our states, we *could* add DSP2/4 stuff... except I don't know what to save, heh.

[Nach]

Well, since we already store extra chip status in our states, we *could* add DSP2/4 stuff... except I don't know what to save, heh.

Let me handle that.

[hydr0x]

Well, since we already store extra chip status in our states, we *could* add DSP2/4 stuff... except I don't know what to save, heh.

Let me handle that.

the chief has spoken

[CyberBotX]

Oh, I would also like zsnes ported to my timex wristwatch

Somehow, I don't think Timex wristwatches have enough buttons to emulate the SNES.

[Noxious Ninja]

The dsp-2 is a coprocessor. You would need to save specific data if you wanted to restore it to the position it was when the state was captured.

Oh, that's all? I figured it was some integral design of the DSP-2 that prevented it.

It would be different if the upd77c25 chip was being emulated but i doubt that will ever happen.

Was that DSP used in SNES games?

[creaothceann]

It doesn't matter (much) how many commercial games use this feature. What about PD ROM authors?