Both work with 6.177h.  VCOM.SYS is for Loopback bit support,
 Scratch Register support, and better performance.  COM.SYS is
 for Modem Reset, 55SX Buffer support.  Both are for better
 COM 3 & 4 support.  This VCOM.SYS requires the matching COM.SYS;
 otherwise, it will cause TRAP 12, Stack Exception.