Search found 9 matches

by nukeykt
Tue Jun 18, 2019 11:06 am
Forum: Sound
Topic: How DAC works ?
Replies: 8
Views: 1374

Re: How DAC works ?

Is not amplification always just 6x base DAC volume as all YM channels output DAC instead of just channel 5 ? That could also be used to do stereo DAC by setting ch0-2 to LEFT and ch3-5 to RIGHT.. but then you need to be perfect sync for DAC update which is almost impossible to do (and it requires ...
by nukeykt
Mon Jun 17, 2019 6:42 am
Forum: Sound
Topic: How DAC works ?
Replies: 8
Views: 1374

Re: How DAC works ?

$2C is a test register (hence why it's "undocumented") and from what I gather the exact behavior differs between the two YM2612 variants used on the Mega Drive. Well, both test registers are same across YM2612 and discrete YM3438. so i assume they're same on ASIC YM3438 too(it's different on YMF276...
by nukeykt
Mon Nov 26, 2018 1:56 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 385411

Re: New Documentation: An authoritative reference on the YM2612

I have started to translate your code to Verilog so we can have this level of accuracy in FPGA too. I don't know whether it will make an audible difference to current JT12 or not, but once the knowledge of the real implementation is published, I think we ought to use it. I understand the original c...
by nukeykt
Sun Nov 25, 2018 6:24 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 385411

Re: New Documentation: An authoritative reference on the YM2612

One FM clock in my code is 6 master clocks. For example in Genesis Plus GX emulator OPN2_Clock is called 1.27(7.67/6) million times per second(for comparison MAME code works at 53.267 KHz). Like real hardware my implementation updates registers within 12 FM ticks. Look carefully to OPN2_DoRegWrite ...
by nukeykt
Sat Nov 24, 2018 7:36 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 385411

Re: New Documentation: An authoritative reference on the YM2612

I agree that it doesn't affect accuracy for well behaved software. What you called one FM cycle, is what I have been calling 24 FM clock ticks, and from the discussion above we have determined that register updates happen in a 12-FM-clock-tick frame. Thus when software changes dynamically register ...
by nukeykt
Sat Nov 24, 2018 4:47 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 385411

Re: New Documentation: An authoritative reference on the YM2612

Sik wrote:
Sat Nov 24, 2018 4:33 pm
But register $2A only has 8 bits...
LSB bit of PCM is mapped to $2C:3.
by nukeykt
Sat Nov 24, 2018 3:06 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 385411

Re: New Documentation: An authoritative reference on the YM2612

On the topic of DAC output: how do DAC bits map to the actual channel output? Because DAC seems to sound too quiet compared to what FM channels can do and I always have to make samples louder to compensate (and that's considering I already make FM channels to be TL = 8 or quieter). 9 bits of PCM da...
by nukeykt
Sat Nov 24, 2018 8:43 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 385411

Re: New Documentation: An authoritative reference on the YM2612

That's an impressive piece of work. I will look at it carefully. Particularly I want to learn more about the undocumented bits. I do not see any schematic in Github, though. Only a very nice SVG file but that is very little information about the chip. Do you have something else? Apologies for sayin...
by nukeykt
Sat Nov 24, 2018 7:10 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 385411

Re: New Documentation: An authoritative reference on the YM2612

Probably my cycle accurate YM3438 emulator(which is basically translation of YM3438 schematic to C code) can give some insight about YM2612/YM3438 internals.