Search found 53 matches
- Mon Jan 09, 2023 4:02 pm
- Forum: Mega/SegaCD
- Topic: Thoughts on BIOS modding.
- Replies: 2
- Views: 32729
Thoughts on BIOS modding.
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.
- Thu Sep 20, 2018 2:51 am
- Forum: Sound
- Topic: Regarding the YM3438 on the Mega Drive...
- Replies: 11
- Views: 18742
Re: Regarding the YM3438 on the Mega Drive...
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 problem...
- Wed Sep 19, 2018 9:11 pm
- Forum: Sound
- Topic: Regarding the YM3438 on the Mega Drive...
- Replies: 11
- Views: 18742
Re: Regarding the YM3438 on the Mega Drive...
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 t...
- Sun Sep 16, 2018 6:02 pm
- Forum: Sound
- Topic: Regarding the YM3438 on the Mega Drive...
- Replies: 11
- Views: 18742
Re: Regarding the YM3438 on the Mega Drive...
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 actually stic...
- Sun Sep 16, 2018 2:57 pm
- Forum: Sound
- Topic: Regarding the YM3438 on the Mega Drive...
- Replies: 11
- Views: 18742
Re: Regarding the YM3438 on the Mega Drive...
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.
- Sun Sep 16, 2018 5:07 am
- Forum: Sound
- Topic: Regarding the YM3438 on the Mega Drive...
- Replies: 11
- Views: 18742
Re: Regarding the YM3438 on the Mega Drive...
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,pcm2612 ; do not w...
- Sat Sep 15, 2018 9:31 pm
- Forum: Sound
- Topic: Regarding the YM3438 on the Mega Drive...
- Replies: 11
- Views: 18742
Regarding the YM3438 on the Mega Drive...
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 set...
- Mon Dec 12, 2016 1:14 pm
- Forum: Mega/SegaCD
- Topic: CDC DMA failing on Kega Fusion?
- Replies: 8
- Views: 15209
Re: CDC DMA failing on Kega Fusion?
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 eit...
- Thu Dec 08, 2016 1:37 am
- Forum: Mega/SegaCD
- Topic: CDC DMA failing on Kega Fusion?
- Replies: 8
- Views: 15209
Re: CDC DMA failing on Kega Fusion?
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 (They'...
- Tue Sep 01, 2015 2:03 pm
- Forum: Hardware
- Topic: Understanding a 139 decoder to wire up 2 roms.
- Replies: 4
- Views: 13716
Re:
/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 exam...
- Fri Aug 28, 2015 12:50 am
- Forum: Announcement
- Topic: Don't forget what SpritesMind is
- Replies: 17
- Views: 46109
Re: Don't forget what SpritesMind is
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 precious re...
- Fri Mar 20, 2015 7:17 pm
- Forum: Hardware
- Topic: Model 1 MD PCB hacks topic
- Replies: 17
- Views: 38225
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, u...
- Fri Mar 20, 2015 5:07 pm
- Forum: Hardware
- Topic: Model 1 MD PCB hacks topic
- Replies: 17
- Views: 38225
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 eighties...
- Fri Mar 20, 2015 5:01 pm
- Forum: Hardware
- Topic: Model 1 MD PCB hacks topic
- Replies: 17
- Views: 38225
- Fri Mar 20, 2015 4:48 pm
- Forum: Hardware
- Topic: Model 1 MD PCB hacks topic
- Replies: 17
- Views: 38225