Versatile ExpressModule Invigorates Servers

Aug. 4, 2005

What will your next server look like? It might have an ExpressModule or two in it. ExpressModules are about the same size as a CompactPCI 3U board. However, ExpressModule uses a less expensive edge connector that sports an x8 PCI Express connection. This should provide plenty of bandwidth, high-performance network interfaces, or hard-disk drives. A large hard drive can fit into a double-wide module.

ExpressModules will show up in their own racks, inside 1U servers, and even in desktop workstations. The form factor is designed to provide high-performance, modular expansion with hot-swap features. It could be used for everything from housing RAID hard-disk drives to Ethernet switch concentrators for a cluster server. It's also an interesting, high-density form factor for blade servers that use off-board storage.

The specification is rather extensive. It even notes the module's hexagonal vent design. On the other hand, the design is rather simple. There are pins for an x8 PCI Express, up to four x1 SATA/SAS storage interfaces, and an I²C-based system management bus (SMbus). The SMbus supports the Intelligent Platform Management Interface (IPMI).

Hot-swap support and status lights are standard, so there will be consistency between different vendors. The ejection lever provides smooth insertion and removal, and it locks the module in place.

ExpressModules will come in single- and double-wide versions. They can use up to 25 and 50 W, respectively. The backplane provides just 12 and 3.3 V. The modules, which can plug into a PCI Express switched backplane, are designed to provide improved electromagnetic interference and cooling.

ExpressModule shipments are expected before the end of the year.

CI-SIG www.pci-sig.org

See associated figure

ExpressModule Specs
Interfaces:	x8 PCI Express, four x1 SATA/SAS, SMbus
Dimensions:	100 by 168 mm single wide: 21 mm double wide: 43 mm
Connector:	edge
Cooling:	forced air
Power:	25-W single, 50-W double

ExpressModule Pins
Quantity	Description
32	x8 PCI Express lanes
2	Differential inputs
40	Ground
8	Power
3	Power status/control
1	Module reset

ExpressModule Pins
Quantity	Description
3	SMbus
1	Presence detect
1	Wake system
1	Attention switch
2	Status LEDs
4	Reserved
98	Total

ExpressModule Pins
Quantity Optional	Description
16	4 SATA/SAS storage
18	Ground
4	Storage control
2	Reserved
40	Total

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William G. Wong | Senior Content Director - Electronic Design and Microwaves & RF

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