HP Vectra XU5 Reference Manual page 25

Local Bus Accelerator (LBX)
The two 82433LX LBX components provide the following data paths:
64-bit data path between the host bus and main memory
32-bit data path between the host microprocessor and the PCI local bus
32-bit data path between the PCI bus and the main memory.
The dual port architecture permits concurrent operations on the host bus and the PCI bus.
There are three write posting buffers and two read prefetch buffers to increase the
performance of the Pentium processor and of PCI master devices. During bus operations
the PCMC commands the LBXs to perform functions such as latching address and data,
merging data, and enabling the output buffers.
Vectra XU Technical Reference System Overview 25