Lucasfilm's sound processor at 1983 had fixed 1.5
ms latency.
they probably had h/w that processed stuff sample-by-sample, rather
than using block-oriented processing the way that general purpose
computers do it.
if you want to match a sample-by-sample design for day, ProTools TDM
h/w has a 1-3 sample delay, no matter what the DSP load.
--p