SpritesMind.Net

After some testing, it appears that the timer counter is only reloaded at the following times: 1. When the counter underflows 2. When the load bit is switched from 0 to 1 (IE, the counter is changed from the stopped state to the running state). The counter does not restart from the last point it was...

Here are a few more things I've found out about the YM2612 over the last few days: 1. Status registers The YM2608 manual describes 3 separate status registers that can be read. Significantly, one of them reportedly returns an ID number for the chip, when the status register is read while register lo...

I've just uploaded a new version of the YM2608 manual translation. It includes too many fixes to detail. Suffice to say, it corrects numerous transcription errors in the previous document (eg, the write wait times on page 14), a bucketload of OCR corrections I missed the first time around which grea...

It is possible to physically toggle the !CART line "on the fly" however, without any side effects. I've used a modified version of your dumping utility MoD to dump problematic devices (like the Sega Channel or the XBand modem) which have exotic address line decoding, and can only be dumped successfu...

TmEE co.(TM) wrote:Your MD has a bit buggy VDP. 5313 is buggy, 5313A is fixed.

Do you know what the difference is? I've been doing all my tests on a 5313, but I have noticed most of my units have a 5313A.

Damn, HDD for a Mega Drive, now that's a mod and a half.

I've just tested, and frequency changes take effect immediately. If you change the frequency for an operator, the new frequency is used for the very next sample, regardless of the current position in the output wave, or the state of the envelope generator. This is consistent with how frequency chang...

Ok then, no emulator that emulates it correctly . :) MAME has an attempt at CSM support implemented, but it doesn't work properly, as is noted in the sourcecode. I've just tried the CSM test ROM in HazeMD, and it just plays a solid tone, which isn't silence, but it isn't correct. I haven't tried MES...

Here's a test ROM which uses CSM to generate a fading, repeating A6 tone: http://nemesis.hacking-cult.org/MegaDrive/Roms/Test/Mine/YM2612/ym2612csmmode.bin Here's the source: http://nemesis.hacking-cult.org/MegaDrive/Roms/Test/Mine/YM2612/ym2612csmmode.asm And here's a sample of the output you get o...

Ok, here's everything I know about CSM mode. The operation is quite simple in the end, but I did a lot of tests searching for unusual behaviour along the way. All this information is based entirely on tests performed on the YM2612 hardware. Enabling CSM mode: CSM mode is a special mode of operation ...

Yep, that should do it in theory. As you said the YM2612 is probably using internally a non signed fixed size register and in some case it underflows. Your fix should emulate it correctly =) well, it doesn't :( I'm probably missing something with this phase increment stuff (this is definitely one o...

I haven't looked for games that use this feature, I've just been experimenting with my own code. If anybody wants to hunt for games which might make use of it, CSM mode is active when the channel 3 mode bits are set to "10", or in other words, when register $27 is set to 10******. CSM mode is not ac...

I've confirmed the presence of the CSM mode in the YM2612, and whatsmore, Kega doesn't emulate it. Hooray, I've found something new! :lol: I've still got more tests to run before I can post a full description of how the CSM mode works, and I'm not going to have time to complete them all tonight, but...

Kudos for your discover ! I searched about this "bug" for a long time, i guess now we just need to figure internal table/reg size for accurate emulation I can tell you right now from initial tests, that the value it overflows to is very close to the maximum frequency value you can set normally (blo...

I just encountered another quirk with the YM2612 which I wasn't fully aware of. This may be common knowledge for people who've worked with the hardware, but I noticed this isn't emulated in Gens, and I wasn't aware of it until I was running these tests either, so I think it should be mentioned. Ther...