Integrated

Circuit

Systems, Inc.

ICS94258

Third party brands and names are the property of their respective owners.

Block Diagram

94258 Rev B - 12/19/01

Functionality

Pin Configuration

48-Pin 300mil SSOP & TSSOP

Recommended Application:

ALI 1644 style chipset

Output Features:

•

2 - CPU clocks (including 1 free running) @ 2.5V

•

13 - SDRAM @ 3.3V

•

7 - PCI (including 1 free running and 1 early selectable

free running) @ 3.3V

•

2 - AGP @ 3.3V

•

1 - IOAPIC 14.318MHz @ 2.5V

•

1 - 48MHz, @ 3.3V

•

1 - REF 14.318MHZ @ 3.3V, (selectable strength 1X or

2X) through I

2C programming

Features:

•

Programmable ouput frequency

•

Programmable ouput rise/fall time

•

Programmable CPU, SDRAM, PCI and AGP skew

•

Real time system reset output

•

Spread spectrum for EMI control typically

by 7dB to 8dB, with programmable spread percentage

•

Watchdog timer technology to reset system

if over-clocking causes malfunction

•

Uses external 14.318MHz crystal

Skew Specifications:

•

CPU - CPU: <250ps

•

PCI - PCI: <500ps

•

SDRAM - SDRAM: <250ps

•

AGP - AGP: <500ps

•

PCI - AGP: <750ps

•

CPU - SDRAM:<350ps

•

CPU - PCI: <3ns

Programmable System Clock Chip for PIII

™ Processor

Notes:

REF0 can be 1X or 2X strength controlled by I2C.

* Internal Pull-up Resistor of 120K to VDD

** Internal Pull-down of 120K to GND

1. This input has 2X drive strength

Note: PCICLK = 33.33MHz , AGP = 66.66MHz

FS3

FS2

FS1

FS0

CPU

SDRAM

0

0

0

0

66.66

66.66

0

0

0

1

66.66

100.00

0

0

1

0

100.00

66.66

0

0

1

1

100.00

100.00

0

1

0

0

100.00

133.33

0

1

0

1

133.33

66.66

0

1

1

0

133.33

100.00

0

1

1

1

133.33

133.33

1

0

0

0

66.66

66.66

1

0

0

1

66.66

100.00

1

0

1

0

100.00

66.66

1

0

1

1

100.00

100.00

1

1

0

0

100.00

133.33

1

1

0

1

133.33

66.66

1

1

1

0

133.33

100.00

1

1

1

1

133.33

133.33