Author: Manfred Schmitz, Technical Director of MEN Mikro Elektronik.
Current PC chipsets support PCI Express as well as Ethernet, SATA/SAS and USB for controlling peripheral components. Today's CompactPCI® CPU boards are based on these modern chipsets, too.
The CompactPCI® specification PICMG 2.0 permits to lead user I/O to the backplane beside the parallel PCI bus . The manufacturers use these user I/O pins to lead these peripheral signals – the modern serial interconnects – to the backplane. Unfortunately the pin assignment has not yet been standardized, so that the intercompatibility of the assemblies is lost. Often even boards by one and the same manufacturer cannot be exchanged among each other. What is more, the 2mm-connector was originally not developed for transmitting differential signals with a speed of 2.5 Gb/s or more.
An extension of the CompactPCI® standard PICMG 2.0, PICMG 2.30 PlusIO (still a draft at present) remedies this. This extension of the standard defines the J2 pin assignment and introduces at the same time a new, 100\% compatible connector, which is also suited for transmission of high frequencies. For this, only a few additional ground signals are required, so that a high number of interfaces can be led to the backplane.
- 4 x PCI Express (one lane each)
- 2 x Ethernet 1000BaseT
- 4 x USB 2.0
- 4 x SATA/SAS
The parallel PCI bus is not changed but is limited to a data bus width of 32 bit. PICMG 2.30 can be used for both single and double Eurocards. A board which supports CompactPCI PlusIO remains 100\% compatible to the current standard, so that it can be used without limitations in existing systems. The high speed connector is also 100\% compatible.
A CPU assembly which supports PICMG 2.30 can also be used as a system slot in a hybrid system. Such a hybrid system can offer Legacy CompactPCI® slots as well as CompactPCI® Express and CompactPCI® Plus slots.
So a small CompactPCI® system can consist of a CompactPCI® system slot (the CPU board), two CompactPCI® peripheral slots for I/O and field bus and two CompactPCI® Plus peripheral slots for a hard disk RAID with hot plug support.
It is planned to offer hybrid systems like this also as standard systems (catalog products). As no switch or bridge boards are required, they are available for practically the same costs as traditional CompactPCI systems. They offer the possibility, however, to integrate modern assemblies beside the conventional boards – an easy way to migrate to modern technologies.