IPMI, VITA 46.11, PICMG ATCA and MicroTCA are standards for managing hardware, and the last three build on the first. IPMI defines the messages, sensor records and FRU inventory format. PICMG 3.0 AdvancedTCA, PICMG MicroTCA and ANSI/VITA 46.11 for VPX each apply IPMI to a different kind of chassis. This article compares IPMI vs VITA 46.11 vs PICMG at a basic level: who manages whom, and what they share.
IPMI: the base specification for servers
The Intelligent Platform Management Interface was written for servers, and v1.5 and v2.0 are the versions in use. In a server, a Baseboard Management Controller (BMC) monitors temperatures, voltages and fans, keeps an event log and stores FRU inventory. Software on the host reaches the BMC through a system interface such as KCS; remote software reaches it over the LAN. The open-source ipmitool works both ways.
IPMI also defines the Intelligent Platform Management Bus (IPMB), an I2C-based bus between management controllers. The chassis standards below make IPMB their main management bus.
PICMG 3.0 AdvancedTCA
AdvancedTCA (ATCA), defined by PICMG 3.0, is a shelf standard for telecom equipment. A Shelf Manager manages the shelf, and every board carries an IPM Controller (IPMC). The Shelf Manager talks to the IPMCs over IPMB-0, which ATCA runs as two redundant buses.
PICMG MicroTCA
MicroTCA puts Advanced Mezzanine Cards (AMCs) directly on a backplane. The MicroTCA Carrier Hub (MCH) contains the MicroTCA Carrier Management Controller (MCMC), and each AMC has a Module Management Controller (MMC).
VITA 46.11 for VPX
ANSI/VITA 46.11 brings the same model to VPX. A VPX chassis has one Chassis Manager, and each plug-in module has an IPMC. They talk over two IPMBs, IPMB-A and IPMB-B, at 100 kHz, with 400 kHz at Tier-3. The VITA 46.11 IPMC runs the FRU state machine from M0 to M7 and switches payload power as the state changes.
VITA 46.11 sorts its requirements into tiers. Tier-1 is the mandatory minimum, Tier-2 adds events and resets, and Tier-3 adds full FRU control, the System Event Log and 400 kHz IPMB. VITA 46.11 Tier-1 vs Tier-2 vs Tier-3 lists what each tier adds.
Side by side
| Standard | Typical system | Central manager | Controller on each board |
|---|---|---|---|
| IPMI v1.5 / v2.0 | Server | BMC | — |
| PICMG 3.0 ATCA | Telecom shelf | Shelf Manager | IPMC |
| PICMG MicroTCA | Shelf of AMCs | MCMC in the MCH | MMC |
| ANSI/VITA 46.11 | VPX chassis | Chassis Manager | IPMC |
What the standards share
- IPMI messages: a request names a network function and a command, and a response starts with a completion code. Get Device ID means the same thing to a BMC and a VPX IPMC.
- Sensor Data Records: sensors are described by SDRs in the IPMI formats.
- FRU inventory: the IPMI FRU Information Storage format, read and written with Read FRU Data and Write FRU Data. The IPMI FRU format explained walks through the layout.
What is different
- Each chassis standard adds its own commands on top of the IPMI message set.
- In ATCA and VPX, the central manager decides when each board's payload power may come on, and both run two redundant IPMBs.
- Each body defines its own records for the FRU MultiRecord Area. VITA records start with the manufacturer ID
0081ACh. - VITA 46.11 sorts its requirements into tiers.
What carries over between them
Because the message set, SDR formats and FRU format are shared, code that encodes and decodes them carries over from one standard to another. A FRU decoder written for server FRU EEPROMs reads the board and product areas of a VPX module. The commands, power rules and bus rules of each chassis standard do not carry over.
The IronKernel VITA 46.11 IPMC implements ANSI/VITA 46.11-2022 on IPMI v2.0, in Rust, on one Arm Cortex-M4F.