Motherboard Layout and Routing Guidelines

2.9.6Intel® 440GX AGPset Clock Layout Recommendations

2.9.6.1Clock Routing Spacing

A Intel® Pentium® II processor / Intel® 440GX AGPset platform requires a clock synthesizer for supplying 100 MHz system bus clocks, PCI clocks, APIC clocks, and 14 MHz clocks. These clocks are supplied by a CK100 clock synthesizer as defined by the CK97 clock/driver specification. The 100 MHz SDRAM DIMM clocks are generated from an I2C controlled clock buffer (CKBF) which produces 18 DIMM clock outputs from a single DCLK output provided by the 82443GX.

To minimize the impact of crosstalk, a minimum of 0.014” spacing should be maintained between the clock traces and other traces. A minimum spacing of 0.018” is recommended for serpentines.

Figure 2-30. Clock Trace Spacing Guidelines

0.014”

0.018”

Clock

2.9.6.2System Bus Clock Layout

System bus clock nets should be routed as point-to-point connections with a 22 Ohm series resistor that is to be placed as close to the output pins on the clock driver as possible (<0.5”).

In a UP system, clock skew between the 82443GX and the processor can be reduced by tying the clock driver pins together at the clock chip and driving the processor and 82443GX from this net with a 10 Ohm resistor at the driver for each. Trace lengths still match the specs defined below.

Layout guidelines: Match trace lengths to the longest trace.

Net

Trace length

min

max

Substrate

 

 

 

 

 

 

 

 

 

 

Clock chip - Processor

H

1.0”

9.0”

3.25”

 

 

 

 

 

Clock chip - 82443GX

H + 3.25”

1.0”

12.0”

NA

 

 

 

 

 

Clock chip - ITP

H + 4.00”

1.0”

13.0”

NA

 

 

 

 

 

2-32

Intel®440GX AGPset Design Guide

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Intel Intel 440GX AGPset Clock Layout Recommendations, Clock Routing Spacing, System Bus Clock Layout, 014 018 Clock

440GX specifications

The Intel 440GX chipset was launched in 1997 as part of Intel's series of chipsets known as the 440 family, and it served as a critical component for various Pentium II and Pentium III-based motherboard architectures. Specifically designed for the second generation of Intel’s processors, the 440GX delivered enhanced performance and supported a range of important technologies that defined PC architectures of its time.

One of the main features of the Intel 440GX was its support for a 100 MHz front-side bus (FSB), which significantly improved data transfer rates between the CPU and the memory subsystem. This advancement allowed the 440GX to accommodate both the original Pentium II processors as well as the later Pentium III chips, providing compatibility and flexibility for system builders and consumers alike.

The 440GX chipset included an integrated AGP (Accelerated Graphics Port) controller, which supported AGP 2x speeds. This enabled high-performance graphics cards to be utilized effectively, delivering many enhanced graphics capabilities for gaming and multimedia applications. The AGP interface was crucial at the time as it offered a dedicated pathway for graphics data, increasing bandwidth compared to traditional PCI slots.

In terms of memory support, the 440GX could address up to 512 MB of SDRAM, allowing systems built with this chipset to run comfortably with sufficient memory for the era’s demanding applications. The memory controller was capable of supporting both single and double-sided DIMMs, which provided versatility in memory configuration for system builders.

Another notable feature of the Intel 440GX was its support for multi-processor configurations through its Dual Processors support feature. This allowed enterprise and workstation computers to leverage the performance advantages of multiple CPUs, making the chipset suitable for business and professional environments where multitasking and high-performance computing were essential.

On the connectivity front, the chipset supported up to six PCI slots, enhancing peripheral device integration and expansion capabilities. It also included integrated IDE controllers, facilitating connections for hard drives and CD-ROM devices.

Overall, the Intel 440GX chipset represented a balanced combination of performance, flexibility, and technology advancements for its time. Its introduction helped establish a foundation for subsequent advancements in PC technology and set the stage for more powerful computing systems in the years to come.