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In detail – special properties of the drivers
The following contains in-depth information for those with the need to know. Less experi-
enced users won't encounter any problems if they skip over this section.
32-bit data transfer
The drivers support a special data transfer format known as "32-bit unpacked". Audio
data streams are transferred to the computer's main memory via the PCI bus. The PCI
bus features 32 "lines" (32-bit). A PC generally takes care to ensure that its data lines are
well-utilized. For this reason, 8-bit audio data is always sent on its way in groups of four
packets (4 x 8 = 32), and 16-bit data (2 x 16 = 32) in groups of two (diagram above).
The situation is a bit more complicated from the processing standpoint with 24-bit audio
data: suddenly there's "only" 24 sweet-sounding bits available, i.e. 8 bits are "missing".
The "24-bit packed" process solves this problem in the following manner: the computer
CPU (your Pentium, for example) divides the 24-bit data into multiples of 32 (middle of
diagram). That costs computing power and isn't really necessary.
The "32-bit unpacked" process fills the remaining bits with zeroes and the driver sends
suitable 32-bit packets on their merry way. Most commonly-used applications currently
support this process, which is particularly easy on the computer's resources (bottom of
diagram).
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PHASE 22 (English)
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