Motherboard Layout and Routing Guidelines

Figure 2-17. Registered SDRAM DIMM Example

SDRAM

SDRAM

SDRAM

SDRAM

SDRAM

SDRAM

SDRAM

DRAMS

 

Register

 

PLL

Register

 

Data

Control

 

 

Clock

 

 

 

There are also “population” rules which need to be observed. To properly adjust memory timings for 100 MHz operation, it is asked of the OEM and end user to populate the motherboard starting with the DIMM located the furthest from the 82443GX.

2.9.1.1Matching the Reference Planes

Providing a good return path for the AC currents induced on the power and ground planes is critical to reducing signal noise. The best way to provide a low inductance return path is to “match” the BGA and motherboard reference planes for a given signal. For example, MD0 is routed on the BGA next to the ground plane. To “match” the reference planes, MD0 should be routed on the Motherboard such that it is closest to the motherboard ground plane. Routing the memory signals in this manner will provide the best possible path for the return currents.

Table 2-17. MDx lines Reference Planes Routing

Memory Data Line

82443GX BGA

Motherboard

Reference Layer

Reference Plane

 

 

 

 

MD0,MD1,MD2,MD3, MD4, MD7, MD11, MD14,

 

 

MD15, MD16, MD17, MD19, MD20, MD21, MD22,

 

 

MD23, MD27, MD28, MD29, MD31, MD33, MD36,

GND layer

GND plane

MD37, MD38, MD40, MD41, MD42, MD43, MD 44,

 

 

MD45, MD48, MD49, MD52, MD53,MD55, MD56,

 

 

MD 57, MD 58, MD61, MD62, MD63, MECC[6:0]

 

 

 

 

 

MD5, MD6, MD8, MD9, MD10, MD12, MD13, MD18,

 

 

MD24, MD25, MD26, MD30, MD32, MD34, MD35,

3.3v VCC layer

3.3v power plane

MD39, MD46, MD47, MD50, MD51, MD54, MD59,

 

 

MD60, MECC7

 

 

 

 

 

2.9.1.2Adding Additional Decoupling Capacitor

Another way to provide a low inductance path for return currents is to provide additional decoupling capacitors next to signal vias. It is not possible to route all the MD lines on a single layer. As a result, some of the MD lines will transition between signal layers through vias. The return currents associated with these signals also require a low inductance path between Vcc and ground. This low inductance path is provided by decoupling capacitors between Vcc and ground. These decoupling capacitors should be placed as close as possible to the signal vias.

Intel®440GX AGPset Design Guide

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Intel 440GX manual Matching the Reference Planes, Adding Additional Decoupling Capacitor, Register Data Control Clock
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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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