Specifications

Appendix B: TDM Mixing and DSP Usage 597
Another example of how TDM II is more effi-
cient than TDM I is to imagine a single HD Core
card with one Engine chip and two Mixer chips.
The DSPs with plug-in instances associated with
the first Mixer don’t need to communicate with
the second Mixer, therefore the time slot num-
bers used can be re-used by the second Mixer to
communicate with other DSPs loaded with
other plug-ins.
DSP Allocation
(TDM Systems Only)
Digital Signal Processing (or DSP) capability is
one of the most powerful elements of your sys-
tem. The DSP chips in your system provide the
real-time processing power for your TDM Mixer
and plug-ins. There is a limit, depending on
your system, to how many functions a single
DSP chip can power at once. This section con-
tains some guidelines for getting the most from
your available DSP capacity.
DSP Allocation Basics
As in the analog world, every send bus or output
mix that you use demands that a summing
mixer exist for that group. On an analog con-
sole, the number of these summing mixers is
fixed by the physical layout of the console. In
the Pro Tools mix environment, this number is
variable, and depends on the number of output
mixes or sends that you choose to create.
Pro Tools allocates DSP power as it is needed to
build the mixers for each session.
We refer to certain mixing or signal processing
functions as “using one DSP” or “using two
DSPs.” This refers to the fact that there are a cer-
tain number of DSP chips on a card, as follows:
Figure 50. TDM bus on Pro Tools HD-series hardware
to previous
HD card
to next
HD card
DSP
1
DSP
1
TDM II bus allows individual connections between DSPs
bi-directionally with 512 time slots each at 44.1 and 48 kHz
HD-series card
512
DSP
2
512
DSP
3
512
DSP
4
512
DSP
5
512
DSP
6
512
DSP
7
512
DSP
8
512
DSP
9
TDM bus
DSP chips on a TDM card
TDM System Card Chips
Pro Tools|HD-
series
HD Core, HD
Accel, or
HD Process
9
Pro Tools24
MIX-series
MIX Core, or
MIX Card
6
Pro Tools|24 DSP Farm 4