Chapter 1. Introduction
5
STD 32 Bus Interface
The ZT 8905 operates in the STD 32 system. In an STD 32 system, data transfers are dynamically
sized for either 8- or 16-bit Standard Architecture or 8-, 16-, or 32-bit Extended Architecture transfers.
All STD-80 compatible memory and I/O boards are supported using 8-bit Standard Architecture
transfers. STD 32 compatible memory and I/O boards are dynamically sensed to determine the width
of the data transfer.
The STD 32 system provides the platform needed for multiple master operation. In a multiple master
system, up to seven ZT 8905 boards share STD bus resources with a fixed or rotating priority granted
by an external bus arbiter, such as the ZT 89CT39.
See Chapter 3, "STD 32 Bus Interface" for a detailed description of the ZT 8905 interface to the
STD 32 bus architecture. The topics discussed include compatibility, interrupt structure, and multiple
master operation.
Pentium Processors
The ZT 8905 supports the second generation Pentium processor family, commonly referred to as the
P54C. The P54C is a 3.3 V processor and operates at higher frequencies and lower power than did
the first generation Pentium (P5). The ZT 8905 operates the external microprocessor bus at either
50, 60, or 66 MHz. The P54C operates internally at 1.5x, 2x, 2.5x, or 3x the microprocessor bus,
supporting potential Pentium internal operation at up to 200 MHz.
The "Pentium Processor Comparison" table below indicates the possible operating frequencies of the
ZT 8905. The PCI bus always operates at 1/2 the external microprocessor bus speed. Not all
processor speeds are offered by Ziatech, nor will Intel necessarily offer all speeds below. Contact
Ziatech for latest product offerings.
The Pentium processor includes 16 Kbytes of cache (referred to as L1 cache). This L1 cache
supports both write-through and write-back cache. A secondary cache (L2 cache) option is planned
to further enhance memory performance. Contact Ziatech for details on availability of the L2 cache
option.
Pentium Processor Comparison
Processor
Speed (MHz)
Internal Clock
Multiplier
External
Processor Speed
PCI Operating
Frequency
90
1.5X
60.0
30.0
100
1.5X
66.6
33.3
120
2.0X
60.0
30.0
133
2.0X
66.6
33.3
150
2.5X
60.0
30.0
166
2.5X
66.6
33.3
180
3.0
60.0
30.0
200
3.0
66.6
33.3
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Содержание ZT 8905
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