Home Page Forums MAME MAME The SNES WIP topic

I can expect that most of them fails their test, but the CG RAM failing is quite bogus...?

Makes sense, it's probably an arbitrary value just so that the SNES-side program knows that the data was sent successfully.


I'm on a roll due to another GB side project I've got, it was pretty straightforward. I'm kind of disappointed that it didn't provide any insight into either what's sent to $6001 or $7800, though.

Hey byuu, you mentioned that you largely took Gambatte's code piecemeal to try to get SGB games working. Could this have anything to do with the issues you were seeing?

http://speeddemosarchive.com/kb/Super_Game_Boy_timing

Edit: Oh, hey, the proper values are already listed on... *shudder*... overclocked.org:

The clock ratio for the Super Game Boy is just the main S-CPU rate, 21.477272MHz, divided by five. It shouldn't matter a whole lot there.

The main transmission protocol is a really, really slow serial thing over the joypad ports. But to send large amounts of data, eg for custom borders, it turns the screen off, then puts a lot of graphics into video RAM, sends a special command and the SGB BIOS uses the next frame's VRAM data for whatever the command was for.

The problem is that $7800 is a streaming auto-increment port, and those commands seem arbitrary and show up whenever. There's never a command-write that says "sync $7800 so the next read starts at offset 0." I think it may be related to the very unusual writes to $6001, but nothing I tried worked. So what kept happening was these commands would read out their own data and end up reading it from the wrong spot, resulting in gibberish custom data, and then the screen video output would get thrown off and the top of the screen would be moved a few lines, kind of like a lousy V-hold or something.

Anyway, on my WIP forum, Fras posted v045 wip09. That one has Super Game Boy support with sound. You should be able to see what I mean from it. The version of gambatte included has a couple of patches to expose the LY-counter, and to load and save to memory instead of disk.

Also, I tried e-mailing Costis to see if he'd be interested in looking into the two registers, but his lack of response seems to indicate he would not. Ah well, worth a try anyway.

Did you also try linking $7800 and the turning on of the gb video hardware? (I suppose you did though)

I don't think that was one of the things I tried, no. I didn't do anything to coordinate $7800 with GB-level events, as I don't really know anything about the GB hardware.

The gb video rendering hardware can be turned off. This allows full access to the gb video ram and is usually used to upload new tile sets for instance. When the gb video rendering hardware is active then during rendering the gb video ram is not accessible from time to time.

Regressions in svn 5824:

-Super Mario World has no sound.
-Rock 'n' Roll Racing resets when entering a race
-Many other games don't even start

What happened?

It seems something wrong. Just check the game : The Legend of Zelda - A Link to the Past

What's wrong with Zelda? I can't see no error in it.