Hybrid backplanes for CompactPCI® and CompactPCI® PlusIO (PICMG 2.30)

2009-07-21, Andreas Lenkisch

PICMG CompactPCI® Serial (CPCI-S.0) brings CompactPCI® into the world of the serial interfaces offered by today's chipsets. By also retaining the CompactPCI® ecosystem, hybrid systems designed to PICMG 2.30 offer a soft transition to the future.

For this purpose a standardised pinout has been defined for the P2 connector of existing CompactPCI® 32-bit CPU (system) slots that was previously left free for user-defined I/O. PCI Express®, USB, serial ATA and Ethernet (10/100/1000 Base-T) serial interfaces are available on it and are taken by a hybrid backplane to the CompactPCI® Serial slots.


The conventional hard metric P2 connector on the CPU has been replaced by the UHM connector from 3M that is footprint and plug compatible. The internal earth shield between the rows and columns of the UHM connector reduces both crosstalk considerably and also the impedance jump of the conventional connector. These characteristics allow the connector to carry signals at over 5 Gbps, which is sufficient for current serial ATA and PCI Express® transmission rates.

Hybrid systems can support up to 7 parallel peripheral slots as previously, and up to 4 serial peripheral CompactPCI® Serial slots. This restriction to 4 slots results from the number of contacts available in the P2 connector. The CPU (system) slot is positioned in the centre.

The pinout for the P2 system slot connector has been defined in such a way that incorrect insertion, e.g. of a 64-bit CPU into a PICMG 2.30 slot, will not damage the boards involved.

Figure 1 shows an example of a hybrid backplane. It is easily recognised: unlike with CompactPCI®, the peripheral CompactPCI® Serial slots require only a relatively small and low-cost connector with six contact rows (basic connector). This carries the power supply, the high-speed PCIe® 1x, SATA and USB (2) signals and, where used, monitoring and control lines. A separate connector is reserved for Ethernet, into which a mezzanine board on the CPU can also be inserted directly, without diversion via the carrier board.

Hybrid backplanes with 4 slots are already available as standard items from stock. Further hybrid backplanes with different numbers of slots and a P47 connector will be introduced shortly.


Photo of a Hybrid backplane


Hybrid backplane, 2x4 slots


Hybrid backplane with P47 connector for CPCI PSUs


Andreas Lenkisch, Principal Engineer Backplanes, Schroff® GmbH, Straubenhardt, Germany

German version on ElektronikPraxis: Hybrid-Backplanes für CompactPCI & CompactPCI Plus

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