Universal Audio UAD POWERED PLUG-INS ver.6.1 - Manual (Page 60)

UAD Powered Plug-Ins Manual - 60 - Chapter 5: Using Multiple UAD Devices
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 devices during tracking may give the extra
pinch of host CPU you need. The buffer size can then be increased and the
UAD device(s) re-enabled for mixing.