Mega-CD/Sega CD FPGA Optical Disc Emulator

[broken]

I wish Todd would have addressed mine and some other questions prior to jumping into the more inflammatory discussion.

I’m sorry, what questions do you have?

[nihilblack]

Does de Mega SD suport EEPROM and SRAM saving like the Mega EverDrive X7?

[Barone]

These ones, Todd. I know some of them are more like pie in the sky but I'm really curious about the possibilities here.
Thanks.

Thanks a lot for taking your time to reply to us here.

Mega SD looks very interesting and I think it's very nice to have an alternative to the original units which are rather expensive and falling apart at this point. I believe Arcade816 project will be using it, for an example; very cool.
From the perspective of someone using CRTs it seems far more interesting than the Mega SG 'cause I can keep the rest of my setup intact.

I have a few questions about it (if they've been answered somewhere else, please, forgive me):
- Did you test Duke Nukem 3D's save with Mega SD? I'm asking because that game uses a bit unusual save RAM size IIRC and some Everdrive MD revisions don't work properly with it. You seem to have saved successfully but then it fails to load your save.


- Do the EEPROM save-based games such as NBA Jam TE (bigger list here: http://www.sega-16.com/forum/showthr...l=1#post619874) require hacking/conversion to battery save to have their saving system working or are they all going to work without any additional trouble for the Mega SD owner?
I'm not talking about save sates.


- Does Mega SD allows you to control Mega Drive/Sega CD volume balance? I mean, games such as Space Adventure Cobra (Lords of Thunder is another offender) have very loud YM2612 instrumentation and if you don't have the Mega Drive 1's volume slider to control it you can barely here the voice overs in the game.
Furthermore, would it be possible to control PSG and FM volume levels independently? That would be one of my wet dreams.


- MSU1 like feature is interesting but is there any chance of implementing something that would make it feasible to re-route Mega Drive games PCM playback to use the Ricoh RF5C164 instead? I think there are far more MD games with garbled PCM playback than games with poor music (not that I wouldn't be enjoying the hell out of MSU1 like support).
Games using SMPS Z80 audio driver usually have really shitty PCM playback, such as Art of Fighting. Being able to play them with decent PCM audio quality would be awesome.


- MD-side overclock breaks Sega CD compatibility when using real hardware. Any chance of Mega SD being more robust/tolerant to it?
I mean, it would allow us to play games which run off the MD's 68000 such as Sonic CD without slowdowns.


Thanks in advance.

[Da_Shocker]

On a slightly different note does anyone have the full romset for the NeoSD? I know you can get them on the Neo-Geo forums but for whatever reason they rejected my membership request.

[Vector]

That was showed on the presentation, timestamp 30:51.

https://youtu.be/8fE0GR9prQE?t=1851

Yes, and unfortunately that is the only youtube content showing or explaining it. A direct feed video like the 10 to 20 of his Mega SD videos with direct line of audio and video he just posted, would let you hear the sound better (compared to the open space air echoed audio of his video camera mic filming the content you time stamped) and many people are interested in this feature from a product and potential homebrew perspective. Glad he will add that to his 10+ video playlist soon =)

[Vector]

Part of me wishes we could just kind of forget / move beyond the 32X at this point. And I say that as someone who bought and enjoyed the 32X when it came out (and still have it connected to this day).

Yes, but I still love Virtua Fighter (16:9 wide screen option in 1995 =0 , might work good today on tvs?) and Virtua Racing Deluxe (since no virtua racing md svp rom support so far) along Space Harrier, Afterburner (only 30 fps instead of Saturn 60?) along with homebrew with Doom64 and Chilly Wolf3D and other games I thoroughly enjoy =) Sure it is probably only 10 solid games I play for it, but the option would be outstanding. I play Virtua Racing 32x a lot !

Also, maybe unfairly when AVGN and his fans of the SNES rival, Genesis, they remember the tower of power supply and cable monster, genesis with sega cd with 32x with wires and power supplies everywhere kind of now. The fact Genesis games came out after 32x died, tend to lean me on the side of it was part of defining Genesis era along with Sega Channel cable service etc. Anyway, now I can watch Game Sack episode on my genesis =)

I mean there is a console/system that now uses a more updated Kega (always wanted that) @ 4:15 of https://www.youtube.com/watch?v=HNvipcHkN3A , maybe that 2019 updated special Kega can be put in Mega SD 2.0 Side Mount, to play the 10 32x games we like? So it uses real genesis, fgpa of sega cd and emus 32x =0

I would also like to say thank you to Todd once again, for not only making this product possible but also taking the time to post on this forum and address things and future support and answer many questions =) Appreciated.

What exact main advantage would the future "side mount Mega SD" have over cart plug in based one now, to a common person like me? Just letting 32x add on rest in cart slot, and maybe faster transfer of info? I don't want to pay $250 for version 1, when version 2 (side loader) might be a better choice.

I'm guessing all threads are now merged and Todd can just reply to questions here now, good.

[broken]

Sorry for the late reply. Had to wait on neodev to write up answers to some of the more technical questions. Plus, you know, weekend.

Did you test Duke Nukem 3D's save with Mega SD? I'm asking because that game uses a bit unusual save RAM size IIRC and some Everdrive MD revisions don't work properly with it. You seem to have saved successfully but then it fails to load your save.

Yes, it works. In fact, that game was not properly detected to use the SRAM overlay mapper, but I've added it to the firmware and it's wornking fine.

Do the EEPROM save-based games such as NBA Jam TE (bigger list here: http://www.sega-16.com/forum/showthr...l=1#post619874) require hacking/conversion to battery save to have their saving system working or are they all going to work without any additional trouble for the Mega SD owner?
I'm not talking about save sates.

Yes, EEPROM carts are supported without patches. We have just one issue with Megaman Willy Wars not properly reading the save, but I hope it will be fixed today.

Does Mega SD allows you to control Mega Drive/Sega CD volume balance? I mean, games such as Space Adventure Cobra (Lords of Thunder is another offender) have very loud YM2612 instrumentation and if you don't have the Mega Drive 1's volume slider to control it you can barely here the voice overs in the game.
Furthermore, would it be possible to control PSG and FM volume levels independently? That would be one of my wet dreams.

Yes. You can adjust CDDA and PCM volumes separately, also from the in-game menu. Default volume is 80% for both, so you have a bit of room to increase it. PSG and FM volumes are internal to the console, so they can't be changed.

MSU1 like feature is interesting but is there any chance of implementing something that would make it feasible to re-route Mega Drive games PCM playback to use the Ricoh RF5C164 instead? I think there are far more MD games with garbled PCM playback than games with poor music (not that I wouldn't be enjoying the hell out of MSU1 like support).
Games using SMPS Z80 audio driver usually have really shitty PCM playback, such as Art of Fighting. Being able to play them with decent PCM audio quality would be awesome.

Yes, the enhanced SSF2 mapper allows mapping the MegaCD PCM chip for use it from the console 68k space, so you can have PCM audio without needing sub cpu programs or any MegaCD related.
Although keep in mind that the PCM chip is quite limited, it's 8 bit PCM, and only 64KB sound ram, so sounds usually need to be streamed into it. I think you can probably use the Z80 to access it too
as long as you keep the PCM mapping set. I think we could extend the memory to 128KB, but it's currently not implemented.

MD-side overclock breaks Sega CD compatibility when using real hardware. Any chance of Mega SD being more robust/tolerant to it?
I mean, it would allow us to play games which run off the MD's 68000 such as Sonic CD without slowdowns.

I suppose CD games crashing when overclocking the MD is caused by the slow WordRAM read. That's what causes the "VDP DMA delay", the WordRAM is so slow that
the requested data arrive when the VDP DMA cycle has already read the bus, so, it's read in the next read cycle but it's just fast enough for the 68k to read it when
using CPU read cycles. However, if you overclock the 68k, this cycle will become shorter, and the data will miss the read window, and the 68k will actually read the previous requested data, causing
issues and crashing if the data was new 68k code to be run.
MegaSD WordRAM is over 10 faster, so delays are inserted to make it behave like the real one. However, we can detect when it's a 68k cycle (because it asserts AS) and return the data immediately so overclock will be possible. Other accesses
that don't assert AS (Z80 or VDP) will still return data at the MegaCD speed. This trick doesn't work when running from the expansion connector, as there is no AS signal there, and it will behave the same than a MegaCD, crashes included


Then about the Side mount cart. It's not a different cart at all, it's just a passive adapter that just remaps some signals and adds some pullup/downs to the address lines to identify it's running from the side, and
do the signal decoding accordingly. You plug this adapter to the expansion port, and then plug your normal MegaSD in the adapter.




Also, I have started working on a FAQ on our forum to address some of the most common questions: https://forums.terraonion.com/viewtopic.php?f=25&t=1006

As time goes on I'll flesh it out with more information.

[Thierry Henry]

[Sik]

Although keep in mind that the PCM chip is quite limited, it's 8 bit PCM, and only 64KB sound ram, so sounds usually need to be streamed into it. I think you can probably use the Z80 to access it too

It can't, nor the Mega Drive's 68000, only the CD-side 68000 can access it (in fact PRG-RAM, WORD RAM and the communication ports are the only things the Mega Drive side can see)

The CD drive is capable of streaming directly into PCM RAM tho, which I imagine is how a lot of games stream in the voice acting scenes (that aren't part of a FMV).

[roce]

I read that as "in our implementation it can".

[Vector]

Great review, thanks for posting. I think I'll buy it or side mount version one day that might have advantages???, when price comes down.

[Team Andromeda]

All the reviews so sound great so far, can't wait for mine to ship

[cleeg]

So, what modifications need to be performed for full Nomad compatibility?

[chilled]

Can it load CHD files instead of .iso or .bin ?

[roce]

CHD is a very complex format that supports multiple compression types. Unlikely.