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furnace/papers/doc/7-systems/sms.md
tildearrow c7ea30dda1 Revert "Revert "Added "c" in "channel" typo and added a TI-99 bit (#551)"" 
This reverts commit 2ffec02e26.
2022-06-22 15:16:19 -05:00

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Sega Master System

the predecessor to Genesis.

surely had better graphics than NES, but its sound (fairly weak, 4ch PSG with A-3 is a lowest tone) is subject of several jokes.

this console is powered by a derivative of the Texas Instruments SN76489.

the original iteration of the SN76489 used in the TI-99/4A computers was clocked much lower at 447 kHz, being able to play as low as 13.670 Hz (A -1). consequentially, pitch accuracy for higher notes is compromised.

effects

  • 20xy: set noise mode.
    • x controls whether to inherit frequency from channel 3.
      • 0: use one of 3 preset frequencies (C: A-2; C#: A-3; D: A-4).
      • 1: use frequency of channel 3.
    • y controls whether to select noise or thin pulse.
      • 0: thin pulse.
      • 1: noise.