Apple says that a plurality of memory lies within the airflow created by the cooling fans and includes modules arranged in a plurality of pairs of memory modules aligned in substantially the same direction as airflow. Each pair has a first memory module and a second memory module, the first and second memory modules each have a length, and the first memory module and the second module are disposed such that the length of the first memory module is in a substantially parallel relationship with respect to the length of the second memory module. A portion of the length of the first memory module is disposed between another pair of memory modules.

The present invention relates broadly to circuit board design. Specifically, the present invention relates to removing heat from components on a circuit board. More specifically, the present invention relates to arranging memory modules to allow improved cooling on the circuit board.

Here's Apple's background on the invention: "Heat is a traditional enemy of circuit board designers in the computer industry. Excessive heat causes components to fail or, at the very least, operate in error. Because heat is such a problem, very clear design rules are followed that minimize the effect heat has on various components on a circuit board. The problem is somewhat more significant when larger geometries are involved, such as found in computers that have multiple central processing units, chipsets, power supply units, memories, and storage devices. Cooling equipment such as heat sinks and fans are used in various configurations to remove heat from the various components, and components may incorporate power saving modes that allow less power to be used (and therefore less heat to be generated) when the component is not being used. Power distribution is always a prime consideration for managing heat within circuit board design. The particular board layout is constrained by distribution of power resulting in heat generation and the efficiency of cooling systems that can be applied in a given board layout. Placement of the components and cooling applications is often dictated by a heat budget that designers adhere to in order to keep components from failing or operating in error.

"Coupled with the problem of heat is the design goal of accommodating more data and accessing it at a faster rate. Memory is often arranged in a grouping or collection of memory modules. Technological advances in memories are of particular concern to board designers. Currently, a popular choice among board designers is the single inline memory module (SIMM), a small circuit board that contains memory chips served by a 32-bit path. Pentium processors from Intel are often used in circuit board design, and require a 64-bit path to memory mandate that SIMMs are installed two at a time. Because they are installed in pairs, it is common to place fans proximate to rows of SIMMs and blow cooler air down the channels defined by the placement of the SIMMs, which absorbs heat from the SIMMs as it passes them."

And here's Apple's summary of the invention: "In one aspect, the present invention provides a printed circuit board that has a plurality of cooling fans and a plurality of memory modules. The cooling fans are arranged to blow air in substantially the same direction. The plurality of memory lies within the airflow created by the cooling fans and includes modules arranged in a plurality of pairs of memory modules aligned in substantially the same direction as airflow. Each pair has a first memory module and a second memory module, the first and second memory modules each have a length, and the first memory module and the second module are disposed such that the length of the first memory module is in a substantially parallel relationship with respect to the length of the second memory module. A portion of the length of the first memory module is disposed between another pair of memory modules arranged in a substantially parallel relationship with respect to each other, wherein the plurality of memory modules is disposed such that airflow is directed along the length of the memory modules between opposing memory modules.

"In another aspect, the present invention provides a low profile server computer, preferably sized to a 1 U chassis. The computer has a storage array, an array of cooling fans; and a plurality of dual inline memory modules. The array of fans separates the storage array from the plurality of dual in line memory modules. The storage array is positioned proximate to the array of cooling fans, which are configured in an alignment to draw air from the storage array and direct the drawn air to channels defined by a plurality of memory modules. The memory modules are aligned in the direction of the flow of the drawn air along the channels. The memory modules are partially interleaved with neighboring memory modules. The interleaved memory modules having partial overlap with at least one neighboring memory module, such that a channel separates the partially interleaved memory modules from all neighboring memory modules.

"In yet another aspect, the present invention provides a method of cooling components on a printed circuit board, by activating a plurality of fans configured to blow air in the same direction across a plurality of memory modules disposed in a substantially parallel relationship with respect to each other and arranged in a staggered relationship, wherein each memory module is positioned partially opposite at least one neighboring memory module, with the neighboring memory module in a substantially parallel orientation with respect to the memory module of the plurality. The orientation defines, for each contiguous memory module pair, a channel between the memory module of the plurality and the neighboring memory module(s), the channel aligned with the direction of air flow through which air is moved by a portion of the fans in the plurality.

"When dual inline memory modules are used in accordance with the present invention, they can be located at a minimum distance of 10.16 millimeters from the closest neighboring memory module."

The inventor is Nayanna Ghantiwala. The graphic below is a plan view of memory modules and cooling fans as used in existing architectures.

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