Specifications

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Chapter 3The PCI Environment

Introduction 3

The PCI (Peripheral Component Interconnect) BUS specifications was created out of the

need to create a simple plug and play mechanism for access I/O resources. PCI has sev-

eral physical and electrical variances. Generally, a PCI based system can have up to 256

PCI buses with upwards of ten(10) PCI devices per bus. Practically, the actual number of

PCI buses and devices is generally restricted by other factors.

The following sections will cover varies aspects of the PCI environment as supported by

PowerMax running under Motorola base platforms. A subset of functionality described in

this chapter is supported by PowerMax on NightHawk Platforms. The supported PCI

subset varies by combinations of NightHawk platforms and their respective PowerMax

OS releases, contact Concurrent Corporation for support when attempting to use PCI

devices on these platforms.

PCI Variants and Form Factors 3

The variants of PCI buses are PCI 32/64 bit, PMC(PCI mezzanine connector)(32/64bit),

and CompactPCI (32/64bit) with either 5.0volt or 3.3volt drivers and running at either

33mhz, or 66mhz bus speeds. Also, the Advance Graphics Port(AGP) specification is a

variant of PCI 64bit/64mhz with special 133/266mhz modes with either 1.5volt or 3.3volt

drivers. Each PCI variant has a unique connector configuration with some implementa-

tions able to support boards that require only a subset of that function.

Generally the 64 bit PCI variants can accommodate 32 bit cards with some restrictions.

The faster PCI bus speeds reduced the number of available slots for add in PCI devices.

Wider PCI buses usually have extra connectors installed to supply connectivity for the

additional signals. PCI buses which support 5.0 volt drivers are keyed differently from

those that which support only 3.3 volt or 1.5 volt bus drivers.

The most common PCI form factors are:

- PCI 32 bit, running between 25 and 33mhz with 5.0volt drivers

- PMC 32 bit, running between 25 and 33mhz with 5.0volt drivers

- Compact PCI 32/64 bit, running at 33mhz with 5.0volt drivers

There are also 64 bit implementations of PCI, PMC and AGP buses. These