SpritesMind.Net

Bumping this as I've added a number of additional links to the OP. I'm sure there's stuff I've missed, so feel free to suggest additions here.

I then checked Galibert's microcode dump (see here , or here for all data he has) and confirmed the same thing.

Oooh, I didn't realize he had gotten that far with decoding the microcode. I'll definitely have to check that out when I get time.

The TL;DR version is: "btst dN,#immed8" shares ...

l_oliveira wrote: Wed Sep 19, 2018 9:11 pm If it is not done that way, the YM3438 actually fails to work on a lot of games.

Which games? I haven't heard of widespread compatibility issues with the Teradrive (which as I previously mentioned has a discrete YM3438), but I'd happy to test some if you know specific games that have problems.

Sik wrote: Sun Sep 16, 2018 4:06 pm This reminds me, the Mega Drive never had a discrete YM3438 (somebody pointed it out to me last night after I had posted >.>).

The Teradrive has an actual YM3438.

Wow, good job with this!
Thanks!

I always wanted to investigate this hardware more, but never found the time.
Still quite a few unknowns if you suddenly find yourself with a bunch of free time :wink: Happy to share test code and/or IDA disassembly projects if that happens (though I know how ...

First, let me start with a big thanks to Nemesis and piroxilin for providing Teradrive disk images and firmware images respectively. Having easy access to software/firmware to reverse was a big help. Now for the info I've figured out:

M68K Memory Map (standard MD hardware omitted)
000000 ...

You should put a non-zero number after the rs.b/rs.w/rs.l as that's the number of elements of that size you're allocating. Not sure if that's causing your syntax error, but you definitely won't get the right results with zero.

sverx wrote: Tue Feb 27, 2018 2:57 pmWhere can I read more details about this? (yeah, I know it's an advanced topic, but I'm curious )

Check out this thread and the linked documentation.

I wonder if the last line is correct - I mean, I can't display color 0 of any of the 4 palettes even if I use the tiles in a background?
It is correct; however, the backdrop color (i.e. what's drawn in the borders or if all the layers above it are transparent) can be any of the 64 CRAM entries ...

I was wondering what values were legal for the IO support field in the standard Sega ROM header so I poked around a bit. This page from the official docs gives quite a few of them, but omits newer peripherals. Looking at the games in my collection I was able to fill in a few gaps and come up with ...

Hm. I wonder if anyone ever transcribed the whole microcode portion of US4325121... having it as a searchable document would be a lot better, as well as less error prone because of how bad the scan is.

I've got just shy of 100 transcribed which is pretty far from complete, though it probably ...

Interesting. The comment does seem to be in line with what the code does (saves the 12 nibbles as 12 bytes in the buffer and pulls the A,B,A',B' state from the 11th byte rather than the 12th). Though it also suggests that A,B,C,D comes in the first nibble with E1,E2,Start,Select in the second. It ...

So I managed to find an XE-1AP while I was in Japan recently and I wrote a little test ROM to better characterize its behavior. First off, big thanks to Eke for emulating this peripheral in Genesis Plus GX as having some idea how this peripheral was supposed to work was a huge time saver when ...

OK, tested on the same Genesis with my UMDK and it works correctly there. Looking at where it seems to get stuck, I think I know what the problem is. You're not filtering out the RESET instruction. While RESET does nothing to the Genesis/MD hardware itself, it does pulse !VRES on the cartridge port ...

For what it's worth, I've seen the same thing on my VA3 Model 1 US Genesis also with a MED v1. Not sure which 68K variant it has off hand. Haven't had a chance to test with my VA6 Model 1 or my Model 3 or using my UMDK yet though. I had no 32X or Sega CD attached during the test.