FD + CWS P = no ALT ACQ feature
CMD + CWS P = ALT ACQ feature
In the old FCC, you can go to "CMD + CWS P" either by deselecting pitch mode or by pushing/pulling on the control column. With the new FCC, appareantly the only way to do this is to deselect the pitch mode.
Personally I find CWS P very good tool during the last levels in climb when heavy - to avoid over-sensitive pitch oscillations of the VNAV SPD mode.