Author: Manfred Schmitz, Chief Technical Officer, MEN Mikro Elektronik
CompactPCI Serial (CPCI-S.0) specifies the additional P0 connector for 6U. Its main purpose is to amplify the power supply of the board. 6U cards are by approx. 130\% larger than 3U cards. This adds space for more electronics, but also adds to the energy consumption.
Power dissipation from 12 V is limited to 60 W for 3U boards. 150 W are permitted for 6U. This is sufficient even to supply power-hungry server chipsets. 150 W is at the same time the physical limit for air cooling of boards that fill up a 19" rack by 4 HP each. Consequently, a 19" enclosure with 20 6U slots could generate a theoretical thermal output of 3000 W.
The new AirMax connectors of CompactPCI Serial do not have special power supply pins. Voltage is supplied using standard connectors suited for signal transmission. The connectors withstand a current load of 1 A per pin at 85 °C. The mechanical design of the connectors has the contacts placed individually, without thermal coupling. If one contact connection heats up more than another, the internal resistance increases, and the current finds its way over cooler contacts. This guarantees that the load is spread equally over all contacts.
The connector type chosen for P0 is identical with P1. By result, it has 72 contacts and could connect up to 24 differential signals. Its pins amplify the 12-V supply, but also the 5-V standby supply. A 6U board may draw a total power of 25 W from the 5 V standby – which is also a concession for server chipsets.
A total novelty lies in two redundant, isolated 48-V power supplies. They are supposed to support different telecom standards, and especially solutions such as Power-over-Ethernet (PoE). A 6U board can provide almost 100 W over the backplane. This hardly has an impact on the thermal balance, because PoE supplies power for external devices, and the 48 V are only controlled.
Two rows of P0 are reserved for two additional Ethernet channels. These add to the eight channels that are defined to form a full-mesh network. While these eight channels build up the multiprocessing network of CompactPCI Serial, the two additional channels can be used for integration into existing CompactPCI systems based on the PICMG 2.16 standard, but also for system administration. Parallel CompactPCI systems still use the IPMB, an I²C bus, to do this. However, Ethernet more and more becomes the standard of choice, here, too. Intel calls this technology AMT. For instance, it can update software even when a system is switched off. The additional Ethernet channels are a really unique feature of CompactPCI Serial and prove that the CPCI-S.0 standard is well-equipped for the future.