HP Vectra XU5 Reference Manual page 26

The PCI/ISA Bridge (PCEB and ESC)
The PCEB and ESC serve as a bridge between the PCI local bus and the ISA expansion
bus. They incorporate the logic for a PCI interface, an ISA interface, a DMA controller that
supports fast DMA transfers, data buffers to isolate the PCI and ISA buses, Timer/Counter
logic, and NMI control logic.
The PCI/ISA bridge also provides decode for the following peripheral devices:
Flash BIOS
Real Time Clock
Keyboard/Mouse Controller
Flexible Disk Controller
Two Serial Ports
One Parallel Port
IDE Hard Disk Drive
Two PCI Accessory Board Slots (supporting 7.5W/3.3V boards).
Vectra XU Technical Reference System Overview 26