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FDS vs. NES sound hardware


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#1 per OFFLINE  

per

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Posted Thu Apr 22, 2010 4:06 PM

I've recently been trying to figure out what the actual differences is between the Famicom disk system and the NES when it comes to sound. As many of you may know, the hardware in the Famicom and NES is more or less identical, but there are some notable differences.

One of the differences is that the pin connector of the famicom has two lines for audio (one for input, the other for output), and this allows cartridges to have their own sound hardware in addition to the sound hardware already present in the CPU. After some searching, I found that some cartridges that used those lines added extra squarewave channels, but some had more advanced soundchips that did FM synthesis (Konami VRC7), Wavetable (Namco N106 and Nintendo FDS), and sawthooth waves (Konami VCR6).

The NES does actually have the audio I/O lines, but they are only present on the expansion-connector hidden by a panel on the underside of the NES. Sadly, no expansions were comercially sold in the western world. Therefore, all western games will only take use off the 5 sound channels present within the CPU (two square-wave channels, one triangle wave channel, one DPCM channel and one noise channel).

Then I decided to take a spectrum analysis of a tune that did sound different on a FDS and a NES. The intro theme of Kid Icarus, to be precice. The reason I chosed this pice is that the FDS version sounds different, but it doesn't sound any differences in what notes are played.

Now to the results (see pictures). A lot is quite similar, like the bass line. I believe it's generated using both the triangle-wave chanel and the DPCM. In addition, the entire composition is almost identical. Then you have the differences. What I noticed first is the long tones in the beginning. On the FDS, those are generated by a squarewave with a duty cycle of 25% (you can see that because it adds an octave of the actual tones). The cartridge version does however use the DPCM instead, something that is quite noticable. Then the rest of the tune is quite simple. From the bass-tone through the rest of the melody, the disk version uses the wavetable channel that is special for the FDS to play the main melody. Since the cartridge version lacks this sound channel, it has to use a normal squarewave channel instead, and only one squarewave channel remains for the submelody. On the FDS the submelody is played by both of the squarevave channels, seperated by a fifth to make it sound more like chords.

As a result, the squarewaves sounds much sharper in the cartridge versions since they aren't mixed together as one "instrument". In addition, the wavetable channel of the FDS has more flexibility than the 4 tone generators in the NES/Famicom, therefor it can generate more complex sounds. My final note is that both versions are great tunes, even the cartridge one may sound a bit cheesy when comparing.

Any coments/thoughts on this topic?

Attached Thumbnails

  • Kid icarus theme spectrum.JPG
  • Kid icarus theme spectrum Explained.JPG


#2 Mitch OFFLINE  

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Posted Thu Apr 22, 2010 7:36 PM

Well, I know you can open up your NES, solder in a resistor on the expansion port and you can hear the extra sounds from the Famicom games. Of course you also need a Famicom to NES adapter that supports it as well.

Mitch

#3 kool kitty89 OFFLINE  

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Posted Thu Apr 22, 2010 9:29 PM

I doubt any did wavetable synthesis, though some may have added additional PCM channels (perhaps ADPCM), though the NES already has a dedicated 7-bit DPCM channel. I'm sure some added variable pulse and not just square. (NES has variable pulse)
Honestly I don't like what some games did with the FDS sound, or rather prefer the remixed sfx and music on the stock NES/Famicom, particularly Zelds -especially sfx. (on-cart sound is another matter)

#4 malducci OFFLINE  

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Posted Thu Apr 22, 2010 11:21 PM

I doubt any did wavetable synthesis, though some may have added additional PCM channels (perhaps ADPCM), though the NES already has a dedicated 7-bit DPCM channel.


The N106 is wavetable. It's just like a GUS sound card ( a unified bank of memory and channels that point into this global memory for which sample to play. The more channels you enable, the more frequency steps you loose. And the max frequency starts dropping). It's also a very similar the Konami SCC and PCE audio chip (which are small wavetable chips). Not the frequency thing, but that you define small samples for it to playback at a specific frequency. MMC5 adds a PCM channel. Not sure what others add as far as PCM (never heard of ADPCM for NES). The DPCM channel on the NES is just 1bit deltas (signed) that accumulate the PCM sound (it's padded to 2bits though. The reason becomes apparent when you look at the frequency table). But the DPCM channel is a bit too coarse in frequency steps to be considered wavetable. And I'm not sure on the specs of the FDS extra channel. (Wavetable is kinda incorrect, it's really referred to as sample-based synth)

I'm sure some added variable pulse and not just square. (NES has variable pulse)


In the NES scene, all pulse modes are referred to as square. It's not the literal sense of the meaning (50% duty cycle). It's square in the sense that it's only "on/off" (square edged pulse), as opposed to anything else (like triangle, saw, sine, or something custom).

Per: That's cool. I've would have never thought to check it out like that. Kudos :D

Edited by malducci, Thu Apr 22, 2010 11:23 PM.


#5 per OFFLINE  

per

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Posted Fri Apr 23, 2010 2:31 PM

I've just done some more research. Now, the worst thing for me is that my NES is a PAL version. Because of this, early NES games like Kid Icarus aren't ajusted for the slower clock speed, making the gameplay, sound, and pitch running 5/6th of the original speed. You may think that a beat reduced to 5/6th of the original isn't much a difference, however, it is. After a little counting, I have determined the underworld theme of kid icarus to run at about 144 beats per second. Reducing this to 5/6 makes a beat of 120 beats per second. Everybody that has at least some experience in music know that vivace has a quite differen effect than moderato, at least when it comes to how well it helps the listener to generate adrenaline. It's like jogging versus walking in a moderate-to-fast tempo.

But since the game runs slower too, it's slightly easier to actually get through areas where you have to be fast.

Anyways, back on topic:
About the NDS sound chip, here is the only decent information I have found: http://famitracker.s...tendo_FDS_sound

Edited by per, Fri Apr 23, 2010 2:51 PM.


#6 kool kitty89 OFFLINE  

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Posted Sat Apr 24, 2010 12:03 AM

The N106 is wavetable. It's just like a GUS sound card ( a unified bank of memory and channels that point into this global memory for which sample to play. The more channels you enable, the more frequency steps you loose. And the max frequency starts dropping). It's also a very similar the Konami SCC and PCE audio chip (which are small wavetable chips). Not the frequency thing, but that you define small samples for it to playback at a specific frequency. MMC5 adds a PCM channel.

Hmm, interesting they would add something that complex on the cart. Is it actual sampled based systhesis with long, complex samples being pulled from ROM and manipulated, or limited programmable wave channels like the PCE? (the SCC seems rather similar to the PCE's simple set-up except using 32 bytes per channel instead of 32 5-bit words)
On the PCE, of course you could used the 5-bit DACs directly for PCM playback or even a software mod player, but that's another matter.

I've seen some sites listing the FDS having an FM synthesis channel.

In the NES scene, all pulse modes are referred to as square. It's not the literal sense of the meaning (50% duty cycle). It's square in the sense that it's only "on/off" (square edged pulse), as opposed to anything else (like triangle, saw, sine, or something custom).

Yes, but many chips can only do plain square (50% duty), like the AY-3-8910/YM2149 or even simpler SN76489, and I think some famicom carts even used such. (FME-07 is supposedly a modified derivative of the AY-3-8910)
Variable pulse gives a LOT more varying sound than plain square, certain pulse widths do a fair approximation of sawtooth waves too.

#7 philipj OFFLINE  

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Posted Mon Jan 6, 2014 7:32 PM

I know this is a bit old topic, but here's something from the n106 cartridge... It sounds good; it sounds like some "Hall & Oats" groove. :) lol

 


Edited by philipj, Mon Jan 6, 2014 7:49 PM.


#8 wood_jl OFFLINE  

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Posted Tue Jan 7, 2014 1:26 AM

I thought this thread was about Feminine Deoderant Spray.

 

Apologies for the misunderstanding, and the misplaced enthusiasm.   Now that I "get it," I choose the NES.  Although if the NES is not available (as some folks here are against this system) , I definitely THEN choose the FDS instead.  Details at 11.






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