Server Base System Architecture
The Server Base System Architecture (SBSA) is a hardware system architecture for servers based on 64-bit ARM processors.{{cite news |author=Peter Bright |date=30 January 2014 |title=ARM finally defines a platform as it sets its sights on the server room |publisher=Ars Technica |url=https://arstechnica.com/information-technology/2014/01/arm-finally-defines-a-platform-as-it-sets-its-sights-on-the-server-room/ }}{{cite news |author=Johan De Gelas |date=29 January 2014 |title=ARM and Partners Deliver First ARM Server Platform Standard |publisher=AnandTech |url=http://www.anandtech.com/show/7721/arm-and-partners-deliver-first-arm-server-platform-standard }}{{cite press release |title=ARM Ecosystem Collaborates to Deliver Initial Server Platform Standard |date=29 January 2014 |publisher=ARM Holdings |url=http://www.arm.com/about/newsroom/arm-ecosystem-collaborates-to-deliver-initial-server-platform-standard.php }}{{cite news |author=Jonathan Corbet |date=5 February 2014 |title=ARM, SBSA, UEFI, and ACPI |publisher=LWN.net |url=https://lwn.net/Articles/584123/ }}
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.{{Cite web|title=Server and Infrastructure|url=https://developer.arm.com/architectures/platform-design/server-systems|last=Ltd|first=Arm|website=ARM Developer|language=en|access-date=2020-05-13}}
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.