Forums  /  Donkey Kong series  /  Donkey Kong '94  /  BGB emulation inconsistencies
  NullSpriteNullSprite

Hey,

After checking out LudwigVonKoopa's run (https://www.speedrun.com/run/zq60jl8y) I noticed an admin notice saying that GBC emulation + initial SGB frame is "probably the best for DK94". I decided to check it out since I got excited, but I don't actually think that is the best way to emulate the game if you are playing on BGB, the reason being that it seems like the game is still being emulated using SGB.

The simple way to check it is by opening the meny and choosing Other > Cart info. If you're using GBC emulation, it will read "emulating as GBC in DMG mode" or something to that effect. However, GBC + initial SGB frame reads "emulating as SGB". Not only that, but the SGB timer lag is also there. When you finish a level and Mario exits the screen, there will be a short sound, a small delay, and then the timer starts ticking down. That small delay is actually a bit longer on SGB timing, and is very noticable when emulating using GBC + initial SGB frame.

Because of this I have some doubts about this method of emulation being GB accurate. I was wondering if there has actually been any research done on this to confirm that it does indeed use GB timing, or if we are just assuming that this is the case?

 
  dadinfinitumdadinfinitum

Hi.

I contacted the developer of bgb prior to posting that comment. I asked:

"do the "SGB + GBC" and "GBC + initial SGB border" emulated systems both emulate the packets that are sent in a Super Game Boy enhanced game (which cause frames of lag)?"

The response was:

"SGB + GBC emulates a system that does not exist, so it may produce undefined behavior (depending on the game)

initial SGB border emulates a SGB until a border is sent (or until a timeout), then it restarts in GBC mode (without SGB emulation) but keeps showing the border."

So, it shouldn't actually be emulating the SGB after the border is sent. If there any sort of lag or delay, it is because it is being ran as the GBC. If you have more specific questions, I'd suggest contacting the developer of bgb (as I did), since I can't answer anything further. Info on how to is here: http://bgb.bircd.org/#email

Now, I think the most ideal system selection in bgb is "Gameboy." I made that comment initially because it seems that a lot of people really care about the SGB border. I'll go ahead and remove my comment, since it's pretty unclear right now.