User`s manual

1.2 Board 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
1
6 ns, 8 ns, 10 ns, 12 ns
1
,15ns
8MB 6 ns, 8 ns, 10 ns, 12 ns, 15 ns
1
Default as shipped
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
There are four 32-bit PCI slots available, with three slots dedicated to PCI and
one shared PCI/ISA slot (see Table 2–3). The PCI bus interface operates at
30.5MHz, which is defined by the 21064A processor’s clock speed.
1.2.7 ISA Interface Overview
The ISA interface provides an expansion bus and the following board 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 bus has two dedicated expansion slots and one shared expansion slot
with the PCI bus. (See Table 2–3.)
Alpha PCI 64–275 Introduction 1–5