Advantages of SNES hardware vs. Genesis hardware

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Originally Posted by evilevoix

The Genesis did not have the Bios to properly marry the "Bittness" of the two chips properly. So unfortunately it is a proper 16 Bit machine but nothing more.

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There's a reason your BIOS statement has been quoted in sigs around here before...

Anyway, to get to picking you apart. The Neo Geo's Z80 only has control over the YM2610, or at least is only ever used with that FM/PCM chip. It is never used for game logic or even graphics. The 68k is seldom used for anything outside game logic. The Genesis is the exact same way. The graphics processor in the Neo Geo is largely what makes it so different and advanced from the Genesis. The BIOS in the Neo Geo has nothing to do with joining the 68k and Z80 together. The most the BIOS ever does is automatically boot power-on self test code before any data is read from the cartridge slot, to make sure the system works properly before proper operation, and determine what kinds of data is implemented in the output graphics and game code (region/censorship). The UniBIOS can do a ton more things, but it's not an SNK-made BIOS.

Also, the TMSS routine in the Genesis can sort of be considered a "BIOS", in the loosest of terms. That is, ROM data that is executed before anything on the cartridge slot.

Unrelated, but somewhat interesting. Only the MVS ever displays it's POST routine. The AES usually doesn't, but I've had it occur once or twice.

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Originally Posted by Joe Redifer

You don't know much about computers, do you?

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He's joking, it's a throwback to the PCE thread.

You could always try the link in his signature.

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Originally Posted by saturndual32

tomaitheous, where can we see some of the stuff you have coded for the PCE?. Are you eventually gonna make a game for it?. Sorry, i dont know much about your background. Could you mention some examples of the "unshown potential" of the PCE?.

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Originally Posted by Team Andromeda

Oh no... not more demo's and Youtube ? Play the real games on real hardware and hear the difference. Even the Amiga out did the Mega Drive when it came to sound and colour and that came out years before the Mega Drive . SEGA could and should have done better with the MD colour pallet and sound sample - But all machines had their pro's and cons

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Tiidos stuff does work on real hardware. It's not cheating or using any additional hardware. It's just a very well coded sound driver. If I remember correctly doesn't Pier Solar use Tiidos Sound Engine for the FM audio?

And no where did we say Eternal Champions music was the best ever, we were talking about the sample quality for the voices. And if I remember correctly it is one that can have 2 samples play at once, but I could be wrong on that bit. It's been a very long time since I played it.

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Originally Posted by Joe Redifer

You don't know much about computers, do you?

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You obviously don't understand the ability of a Neo Geo AES/MVS Memory card slot with a double bios/memory upgrade marrying chips to double the output of the 24 Bit machine 2 48 bits. I suppose it would be possible to double the efforts of the Mega Drive coupled with a Mega CD but the issue would be the Mega Hrtz differences so this is why we got the 32X.

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Originally Posted by Guntz

There's a reason your BIOS statement has been quoted in sigs around here before...

Anyway, to get to picking you apart. The Neo Geo's Z80 only has control over the YM2610, or at least is only ever used with that FM/PCM chip. It is never used for game logic or even graphics. The 68k is seldom used for anything outside game logic. The Genesis is the exact same way. The graphics processor in the Neo Geo is largely what makes it so different and advanced from the Genesis. The BIOS in the Neo Geo has nothing to do with joining the 68k and Z80 together. The most the BIOS ever does is automatically boot power-on self test code before any data is read from the cartridge slot, to make sure the system works properly before proper operation, and determine what kinds of data is implemented in the output graphics and game code (region/censorship). The UniBIOS can do a ton more things, but it's not an SNK-made BIOS.

Also, the TMSS routine in the Genesis can sort of be considered a "BIOS", in the loosest of terms. That is, ROM data that is executed before anything on the cartridge slot.

Unrelated, but somewhat interesting. Only the MVS ever displays it's POST routine. The AES usually doesn't, but I've had it occur once or twice.

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Again I would revisit what I wrote above. Everyone knows that hardware upgrades are capable with memory/bios upgrades to the architecture. Bios allows the chips logic and power to be increased in speed and efficiency and effectively increase the "bittnes" of the unit. The greatest example is of course the PCE, going from Keith Courage to Arcade cards with bios and a reasonable example of AOF is amazing in itself. The Neo Geo Dual chip architecture is "24 Bit" as stated on the box having that leg up over traditional 16 Bit machines and pseudo 16 bit machines. The bios revisions of 1995 implemented by SNK to keep up with the Bit-Wars and double the output to 48-Bit would have trumped that of the PS1 and Saturn however the N64 was on its way and SNK scrapped the Idea in favor of Traditional KOF's and so on.

They dumped the bios revision into the 64-Bit machine from SNK however it flopped although I loved it, particularly beast busters.

You can still see remnants of the "Bit-Wars" phenomenon at your local gas station, just look at the counter and see that little bottle of 5Hr Energy and right next to it was 6Hr Energy, tough choice, quality Vs quantity.

http://i644.photobucket.com/albums/u...f-serious-.jpg

The Genesis - Sega CD - 32X is like a bazillion bit, especially if you multiply the CPUs bitness by the on board oscillators and then square it for good measure.

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Originally Posted by tomaitheous

No. Mira, the master clock of the SNES is 21.47727mhz. There's DMA and there's HDMA. They are not the same, but they will use the same 'channels' - but HDMA only runs during active display. Forget HDMA for now. So DMA only runs during vblank. The speed of DMA (and HDMA) to copy a byte from the cart bus to the A bus is 8 master cycles (regardless if you have fast rom installed on the bus which is 6 master cycles). 8 master cycles is 21.47727 / 8 = 2.68465875mhz. If all you had was vblank or the display was disabled, you could transfer 2,684,658 bytes per second. But that number is kind of useless since we want specifically for vblank periods.

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Okay, I have no idea what the master clock even does. So that is what I was missing.

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Originally Posted by tomaitheous

Ok, assume vblank is 38 scanlines long (224 vertical display setting). How many master cycles are in a scanline? Easy: 21,477,270 / 60 = 357,954.5. So there is 357,954 master cycles per frame. 357954 / 262 = 1366 master cycles per scanline. Since the DMA speed is fixed at 8 master cycles per byte; 1366 / 8 = 170.78 bytes per scanline. 170.78 * 38 scanlines = 6.49k per second. That number doesn't equal 6.3k, but if you subtract 1 scanline from 38, then 37 * 170.78 = ~6.3k. My numbers might be slightly rounded or such, but anyway that's the math for it.

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Awesome. Thank you. I knew I was trying to find the per frame DMA from the top down. I guess I need to study PAL and NTSC signals and their interaction with these consoles more. I just don't know where to start.

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Originally Posted by tomaitheous

@sheath If you really want the most in depth details about the SNES, I recommend contact byuu in one of the forums he hangs out. He wrote the most accurate SNES emulator to date and attention to detail is his thing.

Don't divide 2.68mhz by 8. It's 8 master clock cycles, *not* 8 cpu cycles.

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All I need for this is documentation to site outside of forum comments. I also need to be able to fact check the numbers.

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Originally Posted by tomaitheous

Yeah, the bitness of the VDP means nothing - really. What if you learned that the VDP was built all on 4bit chained logic? It wouldn't change anything 'cause you've played the Genesis and have seen what it can do. It's fun to talk about specs in relation to what can be exploited for the system's advantage, but most of that stuff has already been figured out on both systems. The only thing left to wow gamers on the Genesis is homebrew softs with really good graphic art that looks like it goes beyond the color limitations. And for the SNES, games that appear to tap that 'hidden' speed potential of the stock CPU. Else, it's all been done on both systems. Well, maybe samples on the Genesis but TmEE's got that one handled. That's pretty much why I dev mostly on the PCE/TG16. It had quite a bit of potential that wasn't shown off. So, I get more bang for the buck (my effort) than on other systems. Plus, I love the challenge of the limitations it does have in relation to the SNES and Genesis. So it hits both my coding g-spots :P But I digress...

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Really, for my part, it would only matter in comparison to the TG16, where multiple RE docs make a point of showing the graphics chips as 16-bit. The "bitness" of the VDP versus PPU hasn't come up as far as I have seen. The CRAM limitation of the VDP and Sprite size limits of the PPUs seems much more relevant.

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Those Youtube videos are recorded off of real hardware if they're from Tiido or me.

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Name the game and I'll happily go out and buy it - Real my foot

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Originally Posted by Team Andromeda

Name the game and I'll happily go out and buy it - Real my foot

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It's still running on real hardware, and aside from the Wave Playing engine there's nothing preventing any of those homebrew Z80 sound engines from being used in a real game situation. It's not like 100% of the Genesis's power is going into playing 2 PCM channels with 5 FM and 4 PSG. From how I understand it you are essentially just using the PCM channel is a different way. It's not cheating, it's not unrealistic, it's not unfair, or any of that. It's 100% possible and legitimate.

I was told by someone that goes by Shiru that has coded MD related software, that there are commercial games that use 2-4 PCM channels for the Genesis. I can't think of any that uses 4 though.
One off the top of my head is Skitchin', which iirc uses 2 simultaniously for Guitar and Drums. There are many others that use many PCM channels. The thing about having more than one PCM sample being played back on the Genesis though, is that it has to be done all in software with very proper coding.

That angry bird port uses the 4 PCM Z80 driver of SGDK :
http://www.youtube.com/watch?v=rXQ2hBdMt40
You can easily heard that we have severals PCM samples playing at same time.

The basic 4 PCM Z80 driver (without envelop support) only eat about 60% of the Z80 time so i can easily add both FM and PSG support to it.
That would make 4 PCM 8 bits @ 16 Khz + 5 FM + 4 PSG, and all that on the Z80 cpu leaving the 68k 100% free for the game logic.
If you don't make any operations which retain the 68k bus for a long time then the PCM playback quality is very good.
It is a pity that almost genesis game just did not take care of that (that is why we often observe poor voices PCM quality on megadrive).

Actually a lot of commercials games are able to play 2 PCM samples.
I'm not sure but i believe that the Duke Nukem 3D Z80 driver is able to play FM + 4 PCM at variable pitch (playback is limited to 8 or 4 Khz though).

Couldn't the Master System's SN76489 be abused to play PCM samples ? Not that the quality would be great but I imagine it could be handy for some effects and percussion. Could that technique be added to a more advanced sound driver for MD ?

As far as I have seen from discussions the most advanced PCM sound engine in a commercial game is in Toy Story. Street Fighter II sounds so bad because it has samples in the music, sampled sound effects and sampled voices playing simultaneously with FM, not sure about PSG in that one. Supposedly that isn't more than two channels though and Super Street Fighter II took out the sampled sound effects and has slightly less garbled voices.

I'm really surprised that something like GEMS didn't handle sample timing perfectly, by the time that was commonly used there wasn't any excuse.

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Originally Posted by Joe Redifer

They should have just put another VDP on there with its own RAM to handle backgrounds.

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Or why not another 68000 while they were at it. Or four.

Or how about 16 MB of RAM.

Or maybe a Voodoo 5 5500 GPU.

Everyone would have loved a $29,995 MSRP Mega Drive.