Motherboard Layout and Routing Guidelines

Figure 2-6. Six Layer Board Stack-up With 3 Signal Planes and 3 Power Planes

Z = 60 ohms

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Primary Signal Layer (1/2 oz. cu.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5 mils

 

 

 

 

 

 

 

 

PREPREG

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ground Plane (1 oz. cu.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

18 mils

 

 

 

 

 

 

 

 

 

CORE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Z = 59 ohms

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Inner Layer #1 (1 oz. cu.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8 mils

 

 

 

 

 

 

 

 

PREPREG

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Power Plane #1 (1 oz. cu)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

18 mils

 

 

 

 

 

 

 

 

 

CORE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Power Plane #2 (1 oz. cu)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5 mils

 

 

 

 

 

 

 

 

PREPREG

Z = 60 ohms

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Secondary Signal Layer (1/2 oz. cu)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Total board thickness = 62.4

Additional guidelines on board buildup, placement and layout include:

•For a 4-layer single processor design, double ended termination is recommended for GTL+ signals. One termination resistor is present on the processor substrate, and the other termination resistor is needed on the motherboard. It may be possible to use single-ended termination, if the trace lengths can tightly be controlled to 1.5” minimum and 4.0” maximum.

•For a 6-layer dual processor design, no termination is required on the motherboard for GTL+ signals, as each end of the GTL+ bus is terminated on each processor. If a single Slot 1 is populated in a DP design, the second Slot 1 must be populated with a termination card.

•The termination resistors on the GTL+ bus should be 56 ohms.

•The board impedance (Z) should be between 50 and 80 ohms (65 ohms ±20%)

•FR-4 material should be used for the board fabrication.

•The ground plane should not be split on the ground plane layer. If a signal must be routed for a short distance on a power plane, then it should be routed on a VCC plane, not the ground plane.

•Keep vias for decoupling capacitors as close to the capacitor pads as possible.

2.3Routing Guidelines

This section lists guidelines to be followed when routing the signal traces for the board design. The order of which signals are routed first and last will vary from designer to designer. Some designers prefer routing all of the clock signals first, while others prefer routing all of the high speed bus signals first. Either order can be used, as long as the guidelines listed here are followed. If the guidelines listed here are not followed, it is very important that your design is simulated, especially on the GTL+ signals. Even when the guidelines are followed, it is still a good idea to simulate as many signals as possible for proper signal integrity, flight time and cross talk.

Intel®440GX AGPset Design Guide

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Intel 440GX manual Routing Guidelines
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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.
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