User`s manual

1.2 System Components and Features

Table 1–1 L2 Cache SIMM Sizes

L2 Cache Size Static RAM Access Times

512KB 6 ns, 8 ns, 10 ns, 12 ns, 15 ns

2MB 6 ns, 8 ns, 10 ns, 12 ns, 15 ns

8MB 6 ns, 8 ns, 10 ns, 12 ns, 15 ns

1.2.5 Clock Subsystem Overview

The clock subsystem provides clocks to the 21072 chipset and PCI devices. Two

oscillators provide clocks for the ISA and combination chip functions.

1.2.6 PCI Interface Overview

The PCI interface provides a selectable PCI speed between 25 MHz and

33 MHz (based on the 21064A clock divisor). An Intel 82378ZB Saturn IO

(SIO) chip provides a PCI-to-ISA bridge.

The PCI has three dedicated slots and one shared slot with the ISA.

1.2.7 ISA Interface Overview

The ISA provides an expansion bus and the following system support functions:

• Mouse and keyboard controller functions provided through an Intel 8242

chip

• A National 87312 chip used as the combination chip providing a diskette

controller; two universal asynchronous receiver–transmitters (UARTs); an

integrated device electronics (IDE) interface; a bidirectional parallel port;

and an interface to the utility bus (Ubus) for ISA interrupts and jumper

status

• A time-of-year (TOY) function provided by a Dallas Semiconductor DS1287

chip

• A 1MB ﬂash ROM memory using the Intel 28F008SA chip

The ISA has two dedicated expansion slots and one shared expansion slot with

the PCI.

AlphaPC64 Introduction 1–5