A method is provided for quenching a slurry in a slurry vessel of slurry phase apparatus which comprises a gas distributor arranged to inject a gas into the slurry at a predetermined level, and an apertured solid particles support below the level at which the gas distributor is disposed to inject the gas. A support processor sends a sequence of commands over and FSI interface to a memory-mapped support interface on a processor chip. The source followers may be sensitive to power supply noise at the gate terminal.