Motherboard Layout and Routing Guidelines

2.3.1GTL+ Description

GTL+ is the electrical bus technology used for the Intel® Pentium® Pro processor and Intel® Pentium® II processor system bus. GTL+ is a low output swing, incident wave switching, open- drain bus with external pull-up resistors that provide both the high logic level and termination at the end of the bus. The complete GTL+ specification is contained in the Pentium II processor databook. The specification defines:

•Termination voltage, VTT

•Termination resistance, RTT

•Maximum output low voltage, VOL, and output low current, IOL

•Output driver edge rate when driving the GTL+ reference load

•Receiver high and low voltage level, VIL and VIH

•Receiver reference voltage, VREF, as a function of the termination voltage

•Receiver ringback tolerance

Refer to the 100 MHz GTL+ layout Guidelines for the Pentium® II Processor and Intel® 440GX AGPset for more details.

2.3.2GTL+ Layout Recommendations

This section contains the layout recommendations for the GTL+ signals. The layout recommendations are derived from pre-layout simulations that Intel has run using the methodology described in Section 2.3.7, “Design Methodology” on page 2-11 . Results from the pre-layout simulations are included in this section.

See the Intel® Pentium® II Processor Specification Update for workarounds for any errata that may be present on the particular stepping of the processor used.

2.3.3Single Processor Design

2.3.3.1Single Processor Network Topology and Conditions

The recommended topology for single processor systems is shown in Figure 2-7. In addition to the termination resistor on the Pentium II processor substrate, a termination resistor is placed on the system board. The recommended value for the termination resistor is 56Ω ± 5%.

Figure 2-7. Recommended Topology for Single Processor Design

VTT

 

L4

RTT

 

L3

 

 

 

L2

Intel®

1

 

L1

440GX

Slot

 

AGPset

 

 

2-6

Intel®440GX AGPset Design Guide

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Intel 440GX manual 1 GTL+ Description, 2 GTL+ Layout Recommendations, Single Processor Design
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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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