Search found 49 matches

by Sauraen
Tue Oct 20, 2015 1:27 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

mikejmoffitt wrote:I'd actually love to see a decapping of the Genesis 3 all-in-1 ASIC, if that's available.
You want to donate one?
by Sauraen
Mon Oct 19, 2015 10:55 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

I've done a little more research since my last post, and I'm pretty much on the same page. The wiki at siliconpr0n lists a technique using concentrated sulfuric acid only, and it looks like this may be possible with the facilities I have access to. I will have more information in the coming weeks. W...
by Sauraen
Mon Oct 19, 2015 2:15 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

Cool, can't wait to hear how it goes! My backyard setup would be handy for the long term, and hell it's just plain fun to try, but I have a feeling you'll be able to turn around a result quicker than I'll be able to get my rig up and running, especially with how little time I've had this last year....
by Sauraen
Sat Oct 17, 2015 12:13 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

If you can read the digital output of an operator, it would be very productive to dump with a logic analyzer the output of the carrier with TL at max, with all modulators silenced, to get a decent dump of the sine table used internally. That won't be necessary. Nemesis probably already has it 100% ...
by Sauraen
Fri Oct 16, 2015 3:01 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

Wow, seriously awesome work Sauraen! Thanks! I was hoping to see you here at some point! And I will thank you in return for the years of work on this chip--I wouldn't have known where to begin with the die, nor frankly would have had the interest, without your wonderful details. I'm especially exci...
by Sauraen
Thu Oct 15, 2015 10:43 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

Potentially good news! As a graduate student in electrical engineering at a major research university in the US, I know people with access to some pretty good equipment. I'm actually getting independent study research credit for my work with the YM2612, so I can get access to a micron-level optical ...
by Sauraen
Fri Oct 09, 2015 12:45 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

Well, given the nature of NMOS devices and static power consumption, that's actually what led me to wonder if it was a 2612 in the VDP in the first place. The VDP should be NMOS, and it does get hot, hotter than the NMOS 68K CPU in the machine. Well then... Maybe what's going on is that they put a ...
by Sauraen
Thu Oct 08, 2015 1:29 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

Given that the discrete YM3438 has different behavior than the ASIC one, and the ASIC one is further different from the YM3438 design, are we sure the ASIC one isn't actually a Sega fixed-and-improved YM2612 core? The YM2612 is implemented in depletion-mode NMOS ratioed logic with dynamic gates. It...
by Sauraen
Tue Oct 06, 2015 3:47 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

Thanks, definitely gold informations for anyone developing Z80 driver ;-) You sometime need to write a lot of data to the YM2612 so saving cycles for write is important ! Thanks, but I hope it's right! This is why I keep asking for someone to write some tests and run them on real hardware. I will b...
by Sauraen
Mon Oct 05, 2015 3:18 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

Some writes such as TLs seem to take longer to process than other stuff, I do full software timing in my old sound driver and I always had to have longer delays on TL writes or the data got mangled and I got wrong output. Same deal with the LR flags register. Others seemed to work faster. It doesn'...
by Sauraen
Mon Oct 05, 2015 3:35 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

Definitely very precious informations you're revealing here Sauraen !! The 9th bit of the DAC which is actually present in the test register, wonderful finding :) Thanks! I'm having a lot of fun with this too. :) Something i'm really wondering, you said it would be pretty difficult to predict the b...
by Sauraen
Sat Oct 03, 2015 2:21 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

I'm writing a VHDL equivalent description of the operator unit. This is the only way to express in detail how it works, other than the die shot itself. I drew out some diagrams and these are the final results. There's no concept of a complete cycle for updating a channel, but if such a concept is ar...
by Sauraen
Thu Oct 01, 2015 10:47 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

I played with clocking the YM2612 with a function generator. At a VERY low frequency it seemed to lose its internal state, and it may have been around 1/4. The use of DRAM would explain that. Naturally a high speed clock caused issues as well, though it went remarkably high before issues appeared. ...
by Sauraen
Thu Oct 01, 2015 3:01 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

I've been bashing my head against the operator unit for the last couple days, and here's some results. Some of these things were figured out from the YM2203 die, just because it's easier to read; but I've been confirming critical elements against the YM2612. 1. The YM2612 uses dynamic memory (DRAM) ...
by Sauraen
Tue Sep 29, 2015 3:03 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 859
Views: 392112

Re: New Documentation: An authoritative reference on the YM2612

Two things to mention. First I figured out the unit which allows the Z80 to read data from the YM2612: http://i.imgur.com/QvnRFS9.jpg The unit which outputs the BUSY signal and the two timer overflow flags is elsewhere and not pictured, though there's nothing more to it. (EDIT: it also contains the ...