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Server Base System Architecture

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

Rationale

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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

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  • 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

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

Platform validation

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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

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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

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

Level 3

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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

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

Level 5

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

Level 6

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

Level 7

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

Versions

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Initial public version

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

SBSA Version 3.0

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SBSA Version 3.0 was released on February 1, 2016.

SBSA Version 5.0

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SBSA Version 5.0 was released on May 30, 2018.

SBSA Version 6.0

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SBSA Version 6.0 was released on September 16, 2019.

SBSA Version 6.1

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SBSA Version 6.1 was released on September 15, 2020.

SBSA Version 7.0

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SBSA Version 7.0 was released on January 31, 2021.

SBSA Version 7.1

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SBSA Version 7.1 was released on October 6, 2022.


See also

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References

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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.