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Revision as of 14:59, 28 August 2026

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You can originally make 3 sounds- a 120Hz beep, a 500Hz beep or a 1kHz beep.

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The speaker can be supplied with one of three frequencies derived from the horizontal line frequency of the video circuitry.

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Coming up are recordings of various sounds mentioned.

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On an NTSC machine, with a horizontal line frequency of approximately 15,734.26 Hz:<br>

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4V  = 15,734.26 / 16  ≈ 983.39 Hz<br>

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If you want to make any other sounds try the improved [[Snippet:Playsong|PlaySong]] subroutine, this however sounds like a broken speaker on the early systems. System II has improved support for this and most of these also have sound on the tv (where you can change the volume).

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8V  = 15,734.26 / 32  ≈ 491.70 Hz<br>

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32V = 15,734.26 / 128 ≈ 122.92 Hz<br>

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<br>

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On a PAL machine, with a horizontal line frequency of 15,625 Hz:<br>

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4V  = 15,625 / 16  ≈ 976.56 Hz<br>

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8V  = 15,625 / 32  ≈ 488.28 Hz<br>

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32V = 15,625 / 128 ≈ 122.07 Hz<br>

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<br>

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If you want to make any other sounds or music try the improved [[Snippet:Playsong|PlaySong]] subroutine. It's not optimal for the early systems - it sounds much like a broken speaker... The second generation of systems has improved support for this and most of these also have sound on the tv so you can adjust the volume.

In VES [[Homebrew:Pac-Man|Pac-man]] the "Pac-man theme" is played before start and the PlaySong routine is also used for the other sound effects.  

In VES [[Homebrew:Pac-Man|Pac-man]] the "Pac-man theme" is played before start and the PlaySong routine is also used for the other sound effects.  

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The PlaySong routine doesn't allow for any other computing while it's running, the song data and other computing (moving graphics perhaps) has to be done alternating in small portions if these are to be combined.

The PlaySong routine doesn't allow for any other computing while it's running, the song data and other computing (moving graphics perhaps) has to be done alternating in small portions if these are to be combined.

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As different machines run on different clock speeds (1.78MHz, 2.00MHz etc) the pitch of the sound varies between PAL, NTSC and also between first and second generation PAL machines.

Sound is controlled by the upper two bits of port 5, 00 means silence and then the three standard beeps:

Sound is controlled by the upper two bits of port 5, 00 means silence and then the three standard beeps:

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                 OUTS 5</pre>

                 OUTS 5</pre>

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Sound will decay rather quickly (about 50 ms before quiet) due to the intentional hardware layout.

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You might need a pause after, not to turn sound off immediately and a

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Port needs to reinit to keep the sound on. 

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clr

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                outs 5

@@ Line 2,211: / Line 2,211: @@
 		.byte	$FF, $00, $10, $E9, $1B, $DD, $E5, $00, $00, $00, $00, $00, $00, $00, $00, $00	; 17EF
 		.byte	$00			; 17FF
 		IF 0

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Outputting Sound

Disassembly:Videocart 24