SpritesMind.Net

I'd like to know the opinion of the devs here on this kind of of modification. It involves patching the SUB CPU BIOS to change internal backup behavior and adding a 32KB RAM in place of the original 8KB RAM.

I actually re-installed the YM3438 mod I had made many years ago in one of my MD consoles. I now remember why I undo it. The noise floor was very high and it annoyed me a lot. Anyway, not a single one of my games did fail with it. But I only own Japanese cartridges.

One game I know that have ...

I forgot to mention this:
Consider that people using YM3438 on Mega Drive are actually cheating by piggybacking the YM3438 with the original YM2612 and tying the /RD pin to +5V so the original YM2612 is the one spammed with reads by the system.

If it is not done that way, the YM3438 actually fails ...

We know that the integrated version is not exactly like the YM2612 but it's also not exactly a YM3438 either. Not sure what Yamaha actually did here.


Very likely they had it changed from the original YM3438 design so it doesn't break when the games spam reads on the status register.

I ...

I don't think it's even possible to reach a high enough read rate that would cause the YM3438 to glitch on a PC printer port.

For sake of being illustrative, this is the ASM macro I was using for the YM2612 access:

OPN2: MACRO
super: Driver Driver_PrintInfoImpl

; e = register
; d = value
SafeWriteRegister:
ld a,e
cp 21h
ret z ; block TEST register
cp 27h
jr z,TimerControl ; mask timer control
cp 2AH
jr z ...

Researching on a hardware design to play Mega Drive VGM data on my beloved MSX platform I have been slowly progressing from just the YM2612 to YM2612 + PCM then YM2612 + PCM + PSG. Even after achieving solid results with the YM2612 chip, I never managed to get the YM3438 to work properly on this ...

That behavior is mentioned in one of the service manuals that got released a couple months ago...

They refer to the affected units as "FUNAI units". FUNAI is the company SEGA contracted to build some of their production of MEGA/SEGA CD2 units.

FUNAI units are more common in the US, equipped with ...

Certain motherboards from the SEGA/MEGA-CD2 have a different CDC, based on a NEC MCU. Even SEGA/MEGA-CD1 units with a JVC mechanism do have a different CDC and that cause problems with at least one game.

KEGA Fusion emulates a CD-ROM drive with the SONY CDC.

So some CD BIOSes don't work in it ...

/CE is not enough for a 8Mb Cart.

Better wording for this ...

/CE gives you 4MB of memory window.

If you ignore /CE you will have bus conflict problems on systems with MEGA/SEGA-CD unit attached.

That's why very big games like Super Street Fighter have mapper chip in them. Pier Solar, too, for ...

This forum is a enormous think tank for retro systems programming and research, even the site being focused on SEGA 16bit hardware and peripherals, other systems still benefit enormously from it directly or indirectly.

I don't think I need to say anything else.


Thank you for keeping this ...

I think I know the deal about the VA6.8:

The VA7 ASIC (same as used in the MD2-VA0 for the most part) - the 315-5487 has some issues with PAL mode, and looking at the date stamps on the ICs between a VA7 and a VA6.8, the first has earlier dates than the latter. so maybe it was an EU-only version ...

Somewhat. There was something weird back then in the old times where we got asian games with megakeys, and I think asian MD systems too, but I don't remeber details :|

Japanese SEGA hardware is quite common here because he had a lot of people from here (Brazil) working in Japan through the ...

Jorge Nuno wrote:It's quite rare yes, I had one and yep it was PAL. No idea if it ever came in NTSC

I've never seen it. And I've seen units from all over the world. Of course PAL stuff is rare here. I bet Asian stuff is quite scarce in Portugal. Is that true ?

So that VA6.8 was released when they were almost ready to switch into the chipset with VDP+Bus Arbiter+I/O chips on the 208 pin SMD thing ?

I did not know about that type. PAL only perhaps ?