Electronic Design

Contending With New Standards

Serial interconnects will wreak havoc on bus-oriented architectures like PC/104. This will eventually lead to new form factors like the PICMG (PCI Industrial Computer Manufacturers Group) Advanced Mezzanine Card (AMC) standard.

AMC is a new standard initially targeted at the communications arena, versus the XMC (switched mezzanine card) standard that's designed to bring switch serial interconnects to extend PMC (PCI mezzanine card) designs. XMC started out as the VITA 42 standard, which retains the four PMC connectors for parallel interfaces and adds two high-speed connectors for the serial interconnect.

AMC handles the same kind of serial fabrics as XMC, such as Advanced Switching, RapidIO, InfiniBand, and Gigabit Ethernet. But, AMC also addresses other serial interfaces—PCI Express, Fibre Channel, and Serial ATA. Additionally, it differs significantly from XMC with its hot-swap capability. This led to the AMC cards having an edge connector and a specially designed handle for hot removal and insertion.

The AMC form factor is designed to handle line-card architectures, replacing a typically proprietary format with a standards-based solution. Actually, the AMC standard is rather varied, supporting two heights (full and half) and single- or double-width cards. Carrier boards such as an AdvancedTCA product from Artesyn Technologies (www.artesyncp.com) and SBS (www.sbs.com) will initially be the home for AMC cards. The interesting design aspect is that for switch fabrics, the carrier board simply links the AMC cards to the backplane switch fabric. In this case, the carrier board often contains a switch.

It doesn't take much imagination to see that AMC cards might work very well in their own rack instead of plugging into a carrier board that in turn plugs into an AdvancedTCA rack. This approach is interesting not only for a rack of line cards, but also as a board-level architecture for general embedded applications or blade servers. A single, half-height board can handle 20 W of power and has enough board space for a single-board computer plus a switch-fabric interconnect. This may well move AMC beyond its original target of standardized line cards.

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