3 System Board (P/Ns D3657-63001 and D3661-63001)

Devices on the ISA Bus

Devices on the ISA Bus

ThePCI/ISA Bridge chip (also known as PIIX, or as the system I/O chip, SIO-

A)is an Intel SB82371FB. It is responsible for transferring data between the PCI bus and the ISA expansion bus.

As the ISA bus controller, the chip supports asynchronous ISA bus operation up to 16 MHz. It integrates: two DMA controllers, two interrupt controllers, a timer, a hidden ISA refresh controller, support for the BIOS, data buffers to isolate the PCI and ISA buses, and NMI control logic. It also contains the two-channel PCI IDE controller (which is described on page 76).

The ISA bus handles the following devices:

•Super I/O controller.

•Serial EEPROM.

•System ROM.

•Other ISA accessory devices.

Super I/O Chip (SMC FDC37C932)

The basic input/output control functions are provided by the Super I/O chip, the SMC FDC37C932. This chip is 100% compatible with ISA architecture and contains the following:

•Serial / parallel communications ports.

•Flexible drive controller (FDC).

•Keyboard and mouse controller.

•Real time clock (RTC) and CMOS memory.

Serial/Parallel Communications Ports

The Super I/O chip supports two serial ports and one bidirectional parallel port. The serial ports are high-speed UARTs with 16-Byte FIFOs, and can be programmed as COM1, COM2, COM3, COM4, or disabled.

The parallel port can operate in four modes:

• Standard mode (PC/XT, PC/AT, and PS/2 compatible)

78