Posted: Sat Jun 19, 2010 8:45 am
I wish I could donate some money. But I am totally broke right now . If the donations are accepted for a month or two, I may throw something in.
Sega Megadrive/Genesis development
http://gendev.spritesmind.net/forum/
http://gendev.spritesmind.net/forum/viewtopic.php?f=24&t=386
I saw the result of Chinese crackers. They make decap of chip, find the position security fuse bit and clear it with laser. Then just read the firmware by programmer. Simply brilliant.TmEE co.(TM) wrote:The Flylogic guys seem good. I looked at their blog and how they crack different security measures etc. in chips, lol
Already done. That's how I derived the algorithm I provided in this thread to re-create the bit-accurate sine table.1.) I know the YM2612 has an internal ROM with a sine wave. This has been read out with other FM chips using the test mode, and the YM2612 has a test mode too. Couldn't we use that or at least attempt to?
Well, none I know of that we need to read. The tables I know about are:2.) Are there other tables in the YM2612 we need to read? If so, what?
I don't think there's any data of note in there other than the tables.3.) What ROM data is in the VDP that we intend to recover by decapping?
I think this is still the biggest, unresolved issue concerning correct YM2612 emulation. When I got my first Mega Drive (which was after I used Genecyst and KGEN), I immediately noticed this strange bias in the audio output in quiet passages.HardWareMan wrote:I confirm that! A very noticeable ladder effect is exist.Nemesis wrote:I was going to look at the DAC last, once I've finished examining the other components of the YM2612. I've also noticed the extreme jump between low volume and silence though. I'm sure the answer to that behaviour lies in the DAC.
Thank you, but... isn't the "ladder effect" supposed to occur on the real YM2612 only? Does your MD2 have the external YM2612 and not the integrated one?TmEE co.(TM) wrote:Here's some fragments of a recording form my MD2 I took long ago,
Eke wrote:Here are some extracted text from the previously posted YM3438 manual that is mentionning the DAC, it would be nice if someone could translate them:
Eke wrote:On that topic, some other part of the YM3438 manual I would be curious to have translated (i.e info that are not already covered by YM2608 translated manual):
Something about the read mode (when reading FM address 1,2,3):
An article about differences between Yamaha OPN chips:
Paul Jensen wrote: Didn't I already post translations for some of this stuff in the Spritesmind forums?
I can post a more thorough translation later, but here are some basics:
HTH
- 1. Each slot/carrier is output as a 9-bit value.
- 2.The DAC is 9-bit.
- 3. The chip has a 96 dB dynamic range internally/theoretically, but the DAC is only 9-bit, so the effective dynamic range is 54 dB.
- 4. Due to the lower dynamic range of the DAC, overflows can occur if you set attenuation (TL) too low.
- 5. The minimum wait time between writes to addresses $21 through $B6 is 17 clock cycles.