As with any major architectural transition, PCI Express
introduces a great deal of production risk for notebook designers. To manage
this risk, many original design manufacturers (ODMs) began designing systems
with proprietary module graphics. To support these customers and accelerate the
adoption of PCI Express in notebooks, NVIDIA collaborated with all the
industry’s leading ODMs to create a consistent graphics interface in the form of
MXM, and committed to creating reference designs for all next-generation NVIDIA®
GeForce™ 6 Go Series GPUs using the MXM specification.

To achieve varying degrees of performance for different-sized
systems, the MXM interface describes three types:

  • MXM-I is designed for small form factors with modest
    performance – 4x32M memory devices

  • MXM-II is designed for medium form factors with higher
    performance – 8x32M memory devices

  • MXM-III is designed for the highest-performance systems –
    8x32M high performance memory devices with 256-bit memory interface. For
    Desktop replacement notebook.

Notebooks and modules that comply with these mechanical
specifications will be interchangeable, and thus upgradeable if the chassis is
designed to support field replacement.

The MXM-I and MXM-II reference modules are designed with an
identical thermal mounting interface. This allows a notebook designer to reuse
the same thermal solution for either an MXM-I or an MXM-II module, facilitating
upgrades without replacing the thermal solution. In the future, MXM graphics
modules could be designed with integrated cooling solutions, much like many of
the current generation of AGP graphics modules. In the meantime, graphics
vendors like NVIDIA will provide reference thermal solutions for MXM-I, MXM-II,
and MXM-III modules to assist customers designing MXM notebook systems.

MXM Connector

The most complex issue for defining MXM was defining the
connector. The connector had these requirements:

  • Reliability

  • High signal integrity

  • Small motherboard footprint

  • Low cost

The motherboard footprint is minimal, less than 72 mm long and
11 mm wide. There are several anticipated heights for the MXM connector,
depending on the mechanical constraints of the system. These heights are 5 mm,
2.7 mm, and 1.5 mm. Connector vendors may develop other heights as MXM becomes a
more popular choice.

The 230-pin MXM connector accommodates full 16-lane PCI Express
signals, as well as all display I/O signals. This flexibility lets notebook
manufacturers use one set of I/O connectors on the motherboard, and simply route
the display signals through the MXM connector to the motherboard. The MXM
connector supports the following display I/O signals:

  • 24-bit LVDS display panel, with EDID support

  • VGA

  • S-video output

  • Component HD video output

  • DVI outputs (2)

  • Integrated graphics pass-through