Communication from a processor in a computer system to a remote input/output (I/O) unit in an expansion drawer using a Peripheral Component Interface (PCI) protocol is optimized to improve system performance. An InfiniBand (IB) protocol link is used to couple the I/O unit to the computer system. In one case the computer system uses a PCI to IB bridge to couple from the processor to a corresponding IB to PCI bridge in the expansion drawer which couples to the I/O unit using a PCI link. Intelligence is added to the PCI to IB bridge to optimize communication by assigning selected PCI command sequences to optimized Macro IB commands. The IE to PCI link has like intelligence to receive and convert the Macro IB commands to the corresponding selected PCI command sequences. Optimization is accomplished by either a learning routine or by a logic state machine that generate the· optimized Macro commands. In other embodiments, a modified operating system (OS) or software running on an unmodified OS intercepts PCI commands and generate the Macro IB commands which are sent to the ill to PCI bridge via a host communication adapter (HCA). In other embodiments, device drivers are linked to a library of software routines which intercept the PCI commands. In this case, the library generates the optimized Macro IB commands.