Compaq EV68A specifications Cache and External Interfaces, Introduction to the External Interfaces

Models: EV68A

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4

Cache and External Interfaces

This chapter describes the 21264/EV68A cache and external interface, which includes the second-level cache (Bcache) interface and the system interface. It also describes locks, interrupt signals, and ECC/parity generation. It is organized as follows:

Introduction to the external interfaces

Physical address considerations

Bcache structure

Victim data buffer

Cache coherency

Lock mechanism

System port

Bcache port

Interrupts

Chapter 3 lists and defines all 21264/EV68A hardware interface signal pins. Chapter 9 describes the 21264/EV68A hardware interface electrical requirements.

4.1 Introduction to the External Interfaces

A 21264/EV68A-based system can be divided into three major sections:

21264/EV68A microprocessor

Second-level Bcache

System interface logic

Optional duplicate tag store

Optional lock register

Optional victim buffers

The 21264/EV68A external interface is flexible and mandates few design rules, allow- ing a wide range of prospective systems. The external interface is composed of the Bcache interface and the system interface.

Input clocks must have the same frequency as their corresponding output clock. For example, the frequency of SysAddInClk_L must be the same as SysAddOutClk_L.

21264/EV68A Hardware Reference Manual

Cache and External Interfaces 4–1

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Compaq EV68A specifications Cache and External Interfaces, Introduction to the External Interfaces