4
« on: August 30, 2009, 23:19:12 »
May I make a supposition?
8363Hz was the finest C that Paula could do.
The frequency of C is about 523.25Hz... Upper octaves are 1046.5, 2093, 4186, 8372Hz ...
So, if we have a sample consisting of 16 bytes, and we play it at 8372Hz, we ear a C.
Now, we have an Amiga's dsp called "Paula", able to replay that sample at some rates defined by the time between each byte (the period), and the time unit is "couples of CPU clock ticks". That dsp is clocked by a quartz at exaclty 7159090Hz (in the NTSC version). To rate at 8372Hz, we need to wait 7159090/8372=855.1 ticks between each byte. Once that number rounded to the unit (nearest even number is 856), the real rate played is :
7159090/856 = 8363Hz!
If trackers was born on a PAL amiga, we'd have chosen a period of 848 ticks, making a rate of 7093790/848=8365Hz... Instead, PAL amigas inherited the 856 period, and played a mistuned C at 8287Hz.