PLXX471 is a V3.4.02 patch for ICP.

Correct problem where 3172 ESCON adapter was hanging
with NMI condition.
The problem seems to manifest itself when attached to an Amdohl
mainframe.
The fix is in the Serial Engine code, CSP2CHC0.EXE.
The fix delays setting the data transfer latch until reception of the
accept command response from the channel.