UAD Powered Plug-Ins Manual v5.2 - Just Music

Note: For optimum results, quit any applications using UAD plug-ins before
disabling/enabling cards.
If a UAD Powered Plug-In is loaded on a card then that card is subsequently
disabled, an error message will be displayed. This occurs because a plug-in
is assigned to a card when it is first instantiated. It stays assigned to the same
card until it is de-instantiated (for example, removed from the insert slot).
Host CPU
Using more than one card can cause a slight increase in host CPU requirements,
so disabling unused cards can help you squeeze in a bit more host performance
if you need it. Using additional devices on the PCI bus requires host
resources, so running 15 UAD plug-ins on three cards at five plug-ins per card
may require more host CPU than running the same 15 UAD plug-ins on one
card.
For example, if you are trying to minimize latency during tracking by using a
smaller buffer size (which will increase host CPU) and need a bit more host
CPU, disabling one or more UAD cards during tracking may give the extra
pinch of host CPU you need. The buffer size can then be increased and the
UAD card(s) re-enabled for mixing.
UAD Powered Plug-Ins Manual - 54 - Chapter 5: Using Multiple UAD Cards