The CompactPCI architecture, explained
Desktop PCI, rethought for industry: 3U/6U Eurocard format, 2 mm pin-and-socket connectors, hot swap and up to 8 slots per segment. Here you find the standard, the PICMG 2.x family and the catalog.
What CompactPCI is: PCI in industrial form
CompactPCI adapts the PCI specification to industrial applications that require a smaller, more robust mechanical form factor than the desktop: same electrical layer, Eurocard mechanics.
Boards mount vertically in a card cage, held by connector, guides and a screwed-in face plate: the 2 mm pin-and-socket connector (IEC 1076) is more reliable than the desktop card edge under shock and vibration. Compared to desktop PCI, CompactPCI doubles the slots — 8 versus 4 — and allows multiple bus segments with bridges; hot swap is in the specification, with staged pins for grounding on insertion.
The architecture offers a wide choice of Intel and PowerPC single board computers in 3U and 6U and a complete range of I/O boards and modules: acquisition, fieldbus, avionics interfaces, Ethernet, serial. Ratified as PICMG 2.0 in 1995, it grew as the 2.x family — up to the 2.16 packet switching backplane, which brings switched Ethernet into the backplane.
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What the specification says
The PICMG 2.x family, item by item
The core and the extensions that still matter: hot swap, Ethernet in the backplane, the bridge to serial.4 entries
PICMG 2.0
Core specification · 1995
The base: the PCI bus on a passive Eurocard backplane. On 3U a 220-pin connector (J1+J2) carries power and 32/64-bit PCI signals; 6U adds up to 315 pins for hybrid buses, 8-slot expansions and IEEE 1101.11 rear I/O.
PICMG 2.1
Hot swap
Replacement with the system running: slightly longer pins guarantee ground before signal contact, and ENUM# notifies the host. With the colored coding key — yellow 3.3 V, blue 5 V — the backplane declares its I/O voltage.
PICMG 2.16
Packet Switching Backplane
The industry's first switched-fabric Ethernet backplane architecture: node boards and fabric boards in a star topology (or dual star with two switches), 10/100/1000 full-duplex links, up to 19 nodes. IP clustering, redundancy and chassis failover without cables.
PICMG 2.30
CompactPCI PlusIO
The bridge to serial: PCIe, SATA, USB and Ethernet come out on J2 alongside classic PCI. It is the migration path that prepares CompactPCI Serial.
Classic and 2.16, in a table
What changes when Ethernet enters the backplane.1 tables
Classic cPCI vs PICMG 2.16
From the technical page's comparison table.
| Classic cPCI | cPCI PICMG 2.16 |
|---|---|
| PCI bus | Embedded-standard Ethernet with PCI |
| No Ethernet link on the backplane | 10/100/1000 Mbps Ethernet |
| IPMI over IPMB management | IPMI over LAN management |
| Proprietary RSS | IP clustering, RSS, chassis failover |
| 6U × 160 mm · 0.8″ pitch · 21 slots in 19″ | 6U × 160 mm · 0.8″ pitch · 21 slots in 19″ |
Where CompactPCI works
Machine control, acquisition and transportation: where the installed base still speaks PCI.
Nearby architectures
The serial successor and the Eurocard cousins.
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