Search found 791 matches

by Nemesis
Sat Jun 21, 2008 3:38 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

I've cracked it. I know the cause of the mysterious blip sound in Flashback. I had a thorough play with Gens and the "Game Music Emu" thingamajigy, and based on the modifications made to the Gens core, I was able to trace back the differences between the two, and figure out the cause. The sound crea...
by Nemesis
Thu Jun 19, 2008 5:57 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

Thanks, that makes sense now. I've never seen those symbols for boolean operators before. I think I must have tried every combination of operators except the right one.
by Nemesis
Thu Jun 19, 2008 5:15 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

I think it would be a great idea if the manual was submitted to romhacking.net. Nemesis, you can have the guys at romhacking.net help translate any parts that need clarification (several of them are professionals). Here is a link to the forum that can help: http://www.romhacking.net/forum/index.php...
by Nemesis
Thu Jun 19, 2008 4:59 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

Am I the only one who finds the formula for the N3 bit of the keycode confusing? Here's how the YM2608 manual says the N3 bit is calculated, on page 25: N3=F11・( F10+F9+F8 ) + !F11・F10・F9・F8 This is a boolean calculation, so their operator symbols are confusing me a bit. I don't see how addition has...
by Nemesis
Thu Jun 19, 2008 12:49 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

Ok, so those register pairs are different again. If that's the correct allocation, that would mean both the documents are wrong. Actually, order which I said is same as in YM2608 doc, just reversed by some reason. Actually, after checking again, the order of the registers you confirmed in your hard...
by Nemesis
Wed Jun 18, 2008 2:38 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

Ok, so those register pairs are different again. If that's the correct allocation, that would mean both the documents are wrong. In your testing on the hardware, did you specifically test and confirm the register allocation, or were you just listening to the sound output for the channel as a whole? ...
by Nemesis
Wed Jun 18, 2008 12:19 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

Yeah, that's probably it. I found another phonetic entry in the ADPCM section of "Priscal" which is known to definitely mean prescale. It's the part at the end which is throwing me a bit. It almost seems like it's another word tacked on. I was thinking "priscarar" might mean something along the line...
by Nemesis
Wed Jun 18, 2008 6:10 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

Yeah, I noticed that. I have a feeling that register may not exist on the YM2612, as according to this documentation, the register defaults to 0, which would mean the chip would power up in 3 channel mode. It's definitely worth testing though. They might have just changed the default. There's also t...
by Nemesis
Tue Jun 17, 2008 10:14 pm
Forum: Pico
Topic: Emulating Sega Pico
Replies: 33
Views: 63029

I'd just modify a ROM and run it off the flashcart if I wanted to get a Mega Drive game running on the Pico. There are too many differences to just use PAR codes to patch. The control interface doesn't even work in approximately the same way, it's likely attempts to write to the 0xAXXXXX memory bloc...
by Nemesis
Tue Jun 17, 2008 9:36 am
Forum: Pico
Topic: Emulating Sega Pico
Replies: 33
Views: 63029

I wasn't planning on running regular Mega Drive games on the Pico, although that could be an interesting experiment. What I meant was I could compile some basic test roms for the Pico, eg, to test the behaviour of the PCM chip, and run them on the system using a Mega Drive flashcart.
by Nemesis
Mon Jun 16, 2008 10:34 pm
Forum: Pico
Topic: Emulating Sega Pico
Replies: 33
Views: 63029

Yeah, I can manage that. My second Pico unit arrived last week (the first one was "sacrificed" to make the dumper). I haven't tried it out yet though. I'll power it up and capture some audio sometime this week. BTW, once my new etching tank arrives, I should be able to rig up a reverse adapter: Runn...
by Nemesis
Mon Jun 16, 2008 11:47 am
Forum: Megadrive/Genesis
Topic: 68000 datasheet
Replies: 2
Views: 4441

Thanks, I haven't come across that particular document before. It has some good info on the interrupt processing stage which is a little vague in the official docs available today.
by Nemesis
Sun Jun 15, 2008 12:08 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

Ok, I've just completed a translation of this document, using the OCR function in Adobe Acrobat Professional, and a web-based Japanese translator at http://www.excite.co.jp/world/english which was recommended to me. I've been manually correcting OCR errors along the way, which in some cases meant lo...
by Nemesis
Tue Jun 10, 2008 2:59 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

Looking again at the Sega documentation, the formulae they provide for timer calculation are very different to the numbers from the YM2608 manual. Timer A: 18 * (1024 - TIMERA) microseconds TIMER A = all 1's -> 18usec = 0.108ms TIMER A = all 0's -> 8400usec = 18.4ms Timer B: 288 * (256 - TIMERB) mic...
by Nemesis
Tue Jun 10, 2008 1:44 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 865
Views: 2151765

Fortunately, they do provide clock-independent formulas for calculating frequency values and timer intervals in this manual: F-Number = (144 * fnote * 2^20 / M) / 2^(B-1) fnote: Frequency Data M: Master clock (Hz) B: Octave Data tA = 72 * (1024 - NA) / M NA: 0~1023 M: Master clock (MHz) tB = 1152 * ...