Random emudev bugs list

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byuu
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Random emudev bugs list

Post by byuu » Tue Jun 18, 2019 3:54 pm

Hope this is an okay topic ... I have a few pesky bugs in my emulator, and was curious if anyone else had similar issues, which might save me some time researching them.

1) Popful Mail hangs after the "Sega" boot splash screen. Both CPUs seem to be waiting for the other to say something.

2) Sonic CD occasionally has a row or two of errant tilemap data at the top of the screen during the FMV opening sequence.

3) Lunar: The Silver Star (JP)'s "Game Arts" splash screen seems to run about 30% too fast.

4) the Mega CD 2.00 (JP) BIOS doesn't play any music. But I know it's supposed to have a song. The Sega CD 2.00w (US) BIOS does play music though.

5) Lots of Titan Overdrive II issues:
* there's no soft background hum when you first start the ROM like I hear on the recording of it (but I do hear the pong ball bouncing sounds)
* the sound goes to pure garbled noise after the ship leaves the dock
* after the rain effects ends around 1:48, instead of seeing the sprites I get a big wall of garbled tile data
I stopped at that point, heh.

I thought all of these would be timing issues, and I spent a week getting the cycle timings ~99% accurate down to exact points for prefetching for both the 68K and the Z80 cores, but to no avail. I also added stalls when the Z80 tries to access the 68K bus as 3 Z80 cycles + 11 68K cycles per byte access. I also support blocking the 68K during the load DMA, and tried messing with the DMA transfer rate to no effect.

The things I know I am missing so far are DRAM refresh waits and VDP FIFO emulation.

Any ideas? ^-^;

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Sik
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Re: Random emudev bugs list

Post by Sik » Wed Jun 19, 2019 11:46 am

byuu wrote:
Tue Jun 18, 2019 3:54 pm
5) Lots of Titan Overdrive II issues:
* there's no soft background hum when you first start the ROM like I hear on the recording of it (but I do hear the pong ball bouncing sounds)
It's not trying to output any sounds besides the beeps at that point, any hum you hear is noise (´・ω・`)
byuu wrote:
Tue Jun 18, 2019 3:54 pm
* the sound goes to pure garbled noise after the ship leaves the dock
The sound driver is extremely timing sensitive so expect to run into this a lot (in particular synchronization between 68000 and Z80). I forgot if it also used longword accesses to Z80 like Stuck Somewhere In Time does (where every other byte goes nowhere, it was done because it made bulk transfers faster).
byuu wrote:
Tue Jun 18, 2019 3:54 pm
* after the rain effects ends around 1:48, instead of seeing the sprites I get a big wall of garbled tile data
Implement 128KB VRAM mode. It abuses it to make every other byte go nowhere (since it needs to stream byte-wide data instead of word-wide in this particular scene). Note that this mode doesn't just throw out every other byte but also reshuffles the VRAM address lines.

You should take a look at this https://plutiedev.com/mirror/kabuto-hardware-notes

EDIT: wait you mean the effect that comes after the clouds (my reading skills are awful :​v). Yeah, probably related to timing. In particular, you said that sound went haywire, and the whole demo is timed to it, so the moment sound goes haywire the whole thing is bound to break. You absolutely need to fix that first before moving on.

Still check that link since it has a lot of information relevant for the demo in general.
Sik is pronounced as "seek", not as "sick".

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