Server Base System Architecture

The Server Base System Architecture (SBSA) is a hardware system architecture for servers based on 64-bit ARM processors.^[1]^[2]^[3]^[4]

Rationale

Historically, ARM-based products have often been tailored for specific applications and power profiles. Variation between ARM-based hardware platforms has been an impediment requiring operating system adjustments for each product.

The SBSA seeks to strengthen the ARM ecosystem by specifying a minimal set of standardized features so that an OS built for this standard platform should function correctly without modification on all hardware products compliant with the specification.

Features

CPU features
Memory management
Peripheral access
Interrupts
Watchdog (errant system detection)

Existing specifications for USB, PCIe, ACPI, TPM, and other standards are incorporated to solidify the specification.

Server Base Boot Requirements

Firmware issues are addressed separately in the Server Base Boot Requirements (SBBR) specification.^[5]

Platform validation

The Architecture Compliance Suite (ACS) checks whether an environment is compliant with the SBSA specification, and is provided under an Apache 2 open source license. It is available at https://github.com/ARM-software/sbsa-acs.

Compliance levels

The specification defines levels of compliance, with level 0 being the most basic, and successive levels building on prior levels. In the words of the spec, "Unless explicitly stated, all specification items belonging to level N apply to levels greater than N."

Level 0, 1, and 2

Levels 0, 1, and 2 have been deprecated and folded into level 3.

Level 3

Level 3 contains base-level specifications for:

PE (Processing Element--a core) features
Memory map
Interrupt controller
PPI (peripheral interrupt) assignments
MMU behavior
Clock and timer subsystem
Wake up semantics
Power state semantics
Watchdogs
Peripheral subsystems

Level 4

Extends level 3, e.g. with support for RAS fault recovery extensions of ARMv8.2 spec.

Level 5

Extends level 4, e.g. with support for stage 2 translation control from hypervisor as specified in ARMv8.4.

Level 6

Extends level 5, e.g. with support for speculative execution safety features.

Level 7

Extends level 6, e.g. with support for Arm Memory System Resource Partitioning and Monitoring (MPAM) and Performance Monitoring Unit (PMU) features.

Versions

Initial public version

Initial public version of the SBSA was announced on January 29, 2014.

SBSA Version 3.0

SBSA Version 3.0 was released on February 1, 2016.

SBSA Version 5.0

SBSA Version 5.0 was released on May 30, 2018.

SBSA Version 6.0

SBSA Version 6.0 was released on September 16, 2019.

SBSA Version 6.1

SBSA Version 6.1 was released on September 15, 2020.

SBSA Version 7.0

SBSA Version 7.0 was released on January 31, 2021.

SBSA Version 7.1

SBSA Version 7.1 was released on October 6, 2022.

References

^ Peter Bright (30 January 2014). "ARM finally defines a platform as it sets its sights on the server room". Ars Technica.
^ Johan De Gelas (29 January 2014). "ARM and Partners Deliver First ARM Server Platform Standard". AnandTech.
^ "ARM Ecosystem Collaborates to Deliver Initial Server Platform Standard" (Press release). ARM Holdings. 29 January 2014.
^ Jonathan Corbet (5 February 2014). "ARM, SBSA, UEFI, and ACPI". LWN.net.
^ Ltd, Arm. "Server and Infrastructure". ARM Developer. Retrieved 2020-05-13.

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[1] Peter Bright (30 January 2014). "ARM finally defines a platform as it sets its sights on the server room". Ars Technica.

[2] Johan De Gelas (29 January 2014). "ARM and Partners Deliver First ARM Server Platform Standard". AnandTech.

[3] "ARM Ecosystem Collaborates to Deliver Initial Server Platform Standard" (Press release). ARM Holdings. 29 January 2014.

[4] Jonathan Corbet (5 February 2014). "ARM, SBSA, UEFI, and ACPI". LWN.net.

[5] Ltd, Arm. "Server and Infrastructure". ARM Developer. Retrieved 2020-05-13.

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