Search found 12 matches

by nukeykt
Thu Jul 06, 2023 3:25 am
Forum: Announcement
Topic: Nuked MD - decap-based cycle-accurate Mega Drive emulator (software & FPGA)
Replies: 8
Views: 61033

Re: Nuked MD - decap-based cycle-accurate Mega Drive emulator (software & FPGA)

Recently got FPGA development board and decided to learn Verilog and try to port my emulator using it :D Github: https://github.com/nukeykt/Nuked-MD-FPGA It is under active development. YM3438 and Z80 are already done and were successfully tested on real mega drive board. Currently working on portin...
by nukeykt
Sun May 14, 2023 8:33 am
Forum: Announcement
Topic: Nuked MD - decap-based cycle-accurate Mega Drive emulator (software & FPGA)
Replies: 8
Views: 61033

Nuked MD - decap-based cycle-accurate Mega Drive emulator (software & FPGA)

hi there :) Thought that people over here might be interested in this, so I'm creating a thread. Was working on this since last year with help from folks behind breaks / breaknes projects. This project is basically plain conversion of mega drive circuit into C code, and thus it is extremely accurate...
by nukeykt
Tue Jun 18, 2019 11:06 am
Forum: Sound
Topic: How DAC works ?
Replies: 8
Views: 12728

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: 12728

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: 865
Views: 2149566

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: 865
Views: 2149566

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: 865
Views: 2149566

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: 865
Views: 2149566

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: 865
Views: 2149566

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: 865
Views: 2149566

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: 865
Views: 2149566

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.