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My POKEY experiments using nonstandard settings


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17 minutes ago, patjomki said:

Taking all CPU power is prohibited. ?

 

So, how can I get variable duty cycle?

 

Or is there a mistake in the wikipedia article?

 

https://en.wikipedia.org/wiki/POKEY#Features

"Per-channel volume, frequency, and waveform (square wave with variable duty cycle or pseudorandom noise)"

 

Two tone is an "overlaid" result of two 16 bit channels. The have to be set "modulo", to get a recognizable waveform. If the frequency of both channels isn't set correctly, you just get weird noise. This makes variable "duty cycles" impossible.

 

You could build those Duty Cycles using software as ROger wrote.

But you also can do that, using the "Filter" to produce variable Duty Cycles. "Filter" is needed, because there is a direct common start programmable.

Using Cancelling to build those Duty Cycles  is much more problematic, as the Start of every Channel isn't 100% to handle.  

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1 hour ago, emkay said:

Two tone is an "overlaid" result of two 16 bit channels. The have to be set "modulo", to get a recognizable waveform. If the frequency of both channels isn't set correctly, you just get weird noise. This makes variable "duty cycles" impossible.

 

You could build those Duty Cycles using software as ROger wrote.

But you also can do that, using the "Filter" to produce variable Duty Cycles. "Filter" is needed, because there is a direct common start programmable.

Using Cancelling to build those Duty Cycles  is much more problematic, as the Start of every Channel isn't 100% to handle.  

What if you use that timer reset trick pavros discovered for $Cx mod 3 bass?

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48 minutes ago, Synthpopalooza said:

I am actually going to experiment with hi pass plus SKCTL next.  Try to see what modulating the first two channels with hi pass gets me.

 

 

This tune is using 2 tone with generator 4 and the high cymbal sound is high pass .

The Bass , btw. ist using an approximation, to warble through all orbits of the bass generator. In the last seconds of the tune it changes to Filter modulation . 

It is done in the patch 8 version of Analmux'  RMT patches. 

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2 hours ago, Synthpopalooza said:

What if you use that timer reset trick pavros discovered for $Cx mod 3 bass?

Pavros syncs timers to polynomial generators. For full control over PWM with filter you need something different. You need to sync 2 channels to each other. Typically you will sync 1 and 3, and use "high-pass" filter on those.

You can use STIMER, or setting frequency to 0 for some time. That time can be greatly decreased by setting channel 1 and 3 to 1.79MHz source. That can't be done with channels 2 and 4 though.

After you reset both channels, you set them them to different frequencies for some defined time. During that time the phases of the two channels will gradually shift away from each other. You can control how much by the frequency difference and the time. Then you set them to the same frequencies.

 

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52 minutes ago, Synthpopalooza said:

Altirra emulates this correctly too i think

At the moment I don't know about anything which Altirra doesn't emulate. I haven't tested some of these thing of yours though on real hardware.

Might be useful if you report any discrepancies.

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8 hours ago, R0ger said:

At the moment I don't know about anything which Altirra doesn't emulate. I haven't tested some of these thing of yours though on real hardware.

Might be useful if you report any discrepancies.

I think this particular case still needs work?

 

 I tried to download the latest altirra 3.2 to check but had config issues (crash on boot with any os), so not sure.

 

I think the trace on here is from that, but not 100%. Pokey vs EclaireXL in that case.

 

http://www.64kib.com/redmine/issues/67

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6 hours ago, foft said:

I think this particular case still needs work?

 

 I tried to download the latest altirra 3.2 to check but had config issues (crash on boot with any os), so not sure.

 

I think the trace on here is from that, but not 100%. Pokey vs EclaireXL in that case.

 

http://www.64kib.com/redmine/issues/67

Interesting. You have to reset Altirra settings sadly. I had the same issue.

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I tried Altirra 3.2 (oddly it worked after I rebooted my pc!) and confirmed it differs from my 600XL (with an original pokey). Altirra and pokeymax in the same 600XL match, so its not down to the post-pokey circuitry. 

Edited by foft
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So here are a couple of renditions of the Area 1/Area 3 theme from the NES shooter Zanac

 

zanac1.mp3

 

zanac2.mp3

 

Both use 2-tone mode ... in the first instance, channel 1 is silenced.  In the second, channel 1 is permitted to play the carrier frequency atop the modulated one.  This improves the sound, but at a cost:  Channel 1 also feeds through the other channels, and when it decays, it puts an awkward volume stutter into the tune.  Any ideas how to fix this?

 

Binaries below:

 

 

zanac.asm zanac.s zanac2.asm zanac2.s

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And another ... the overworld theme from Super Mario World.

 

super mario world - overworld theme.mp3

 

This one uses AUDCTL=$60 and two tone mode on $Ax, which is the very famous "Save to Cassette" setting familiar to all of us. :) A very ringy bell timbre.

 

The note table for this setting is up in the thread. :)

 

 

marioworld1.asm marioworld1.s marioworld1.xex

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  • 2 weeks later...

You know that all your energy will end in the nirvana?

On the Atari  almost no one wants music. There is a dedicated detune, they like. If you correct things, 99% of them will ignore or dislike it. 

 

This is the most advanced peace of music , playable on a real Atari. See the reaction to it.

 

 

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2 hours ago, emkay said:

You know that all your energy will end in the nirvana?

On the Atari  almost no one wants music. There is a dedicated detune, they like. If you correct things, 99% of them will ignore or dislike it. 

 

This is the most advanced peace of music , playable on a real Atari. See the reaction to it.

 

 

Nothing wrong with this tune, but “most advanced” is highly subjective.

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