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MiSTer-devel / MacPlus_MiSTer

Macintosh Plus for MiSTer
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Missing sound effects on legacy audio (Lode Runner, ...) #7

Closed jsmolina closed 1 day ago

jsmolina commented 3 years ago

Lode runner has missing sounds effects for 'laser', 'pickup money', ...

It has music effect for ending level, so I guess it's something related to samples.

Tried at 8 MHz and same disk image works perfectly on mini vmac.

jsmolina commented 2 years ago

already failing on latest versions

jsmolina commented 1 year ago

macplus was known to have 6522 VIA chip.

The sampled sound engine piggybacked on the video circuit. As the raster scan returned from the right side of the screen to the left, one byte of data was placed into a PWM generator instead of the screen. This provided 8-bit sampled monaural sound sampled at the 22.25 kHz horizontal blanking rate. General purpose 6522 outputs could mute the sampled sound, or set its volume to one of 8 levels of attenuation.

A square wave generator was included on the 6522. One of its two timer circuits could be set to toggle the mute output periodically. This could produce frequencies higher than 11 kHz.

jsmolina commented 1 month ago

hardware described here: https://archive.org/details/Guide_to_the_Macintosh_Family_Hardware_Second_Edition/page/71/mode/2up

darylrichards commented 2 weeks ago

Fix contributed...

https://github.com/MiSTer-devel/MacPlus_MiSTer/pull/12