Efficiency; Figure 5-4 Waveform With Multiple Cycles - Commodore Amiga Hardware Reference Manual

128
-127
Samples taken over time -
Always requires an even
number of samples -
Shows a case in which a high-frequency waveform may need more than one full cycle to accurately
reproduce the periodic waveform
Figure 5-4: Waveform with Multiple Cycles
EFFICIENCY
A certain amount of overhead is involved in the handling of audio DMA. If you are try-
ing to produce a smooth continuous audio synthesis, you should try to avoid as much of
the system control overhead as possible. Basically, the larger the audio buffer you pro-
vide to the system, the less often it will need to interrupt to reset the pointers to the top
of the next buffer and, coincidentally, the lower the amount of system interaction that
will be required. If there is only one waveform buffer, the hardware automatically resets
the pointers, so no software overhead is used for resetting them.
The "Joining Tones" section illustrated how you could join "ends" of tones together by
responding to interrupts and changing the values of the location registers to splice tones
together.
If
your system is heavily loaded, it is possible that the response to the inter-
rupt might not happen in time to assure a smooth audio transition. Therefore, it is
advisable to utilize the longest possible audio table where a smooth output is required.
This takes advantage of the audio DMA capability as well as minimizing the number of
interrupts to which the 68000 must respond.
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Audio Hardware 153