SPARC

SPARC is a reduced instruction set computer instruction set architecture originally developed by Sun Microsystems. Its design was strongly influenced by the experimental Berkeley RISC system developed in the early 1980s. First developed in 1986 and released in 1987, SPARC was one of the most successful early commercial RISC systems, and its success led to the introduction of similar RISC designs from many vendors through the 1980s and 1990s. After acquiring Sun, Oracle Corporation ended SPARC development in 2017.

Description

By the mid-1980s the computer industry's consensus was that RISC had a much better price/performance ratio than traditional CISC architecture. Workstation vendor Sun Microsystems decided to move to RISC as fast as possible from the Motorola 68000 series of processors.
The first implementation of the original 32-bit architecture was used in Sun's Sun-4 computer workstation and server systems, replacing their earlier Sun-3 systems based on the Motorola 68000 series. SPARC V8 added a number of improvements that were part of the SuperSPARC series of processors released in 1992. SPARC V9, released in 1993, introduced a 64-bit architecture and was first released in Sun's UltraSPARC processors in 1995. Later, SPARC processors were used in symmetric multiprocessing and non-uniform memory access servers produced by Sun, Solbourne, and Fujitsu, among others.
The design was turned over to the SPARC International trade group in 1989, and since then its architecture has been developed by its members. SPARC International is also responsible for licensing and promoting the SPARC architecture, managing SPARC trademarks, and providing conformance testing. SPARC International was intended to grow the SPARC architecture to create a larger ecosystem; SPARC has been licensed to several manufacturers, including Atmel, Bipolar Integrated Technology, Cypress Semiconductor, Fujitsu, Matsushita and Texas Instruments. Due to SPARC International, SPARC is fully open, non-proprietary and royalty-free.
As of 2024, the latest commercial high-end SPARC processors are Fujitsu's SPARC64 XII and Oracle's SPARC M8 introduced in September 2017 for its high-end servers.
On September 1, 2017, after a round of layoffs that started in Oracle Labs in November 2016, Oracle terminated SPARC design after completing the M8. Much of the processor core development group in Austin, Texas, was dismissed, as were the teams in Santa Clara, California, and Burlington, Massachusetts.
Fujitsu will also discontinue their SPARC production, after one "enhanced" version of Fujitsu's older SPARC M12 server in 2020–22, end-of-sale in 2029, of UNIX servers and a year later for their mainframe and end-of-support in 2034 "to promote customer modernization".

Features

The SPARC architecture was heavily influenced by the earlier RISC designs, including the Berkeley RISC I and II from the University of California, Berkeley and the IBM 801. These original RISC designs were minimalist, including as few features or op-codes as possible and aiming to execute instructions at a rate of almost one instruction per clock cycle. This made them similar to the MIPS architecture in many ways, including the lack of instructions such as multiply or divide. Another feature of SPARC influenced by this early RISC movement is the branch delay slot.
The SPARC processor usually contains as many as 160 general-purpose registers. According to the "Oracle SPARC Architecture 2015" specification an "implementation may contain from 72 to 640 general-purpose 64-bit" registers. At any point, only 32 of them are immediately visible to software — 8 are a set of global registers and the other 24 are from the stack of registers. These 24 registers form what is called a register window, and at function call/return, this window is moved up and down the register stack. Each window has eight local registers and shares eight registers with each of the adjacent windows. The shared registers are used for passing function parameters and returning values, and the local registers are used for retaining local values across function calls.
The "scalable" in SPARC comes from the fact that the SPARC specification allows implementations to scale from embedded processors up through large server processors, all sharing the same core instruction set. One of the architectural parameters that can scale is the number of implemented register windows; the specification allows from three to 32 windows to be implemented, so the implementation can choose to implement all 32 to provide maximum call stack efficiency, or to implement only three to reduce cost and complexity of the design, or to implement some number between them. Other architectures that include similar register file features include Intel i960, IA-64, and AMD 29000.
The architecture has gone through several revisions. It gained hardware multiply and divide functionality in version 8. 64-bit were added to the version 9 SPARC specification published in 1994.
In SPARC version 8, the floating-point register file has 16 double-precision registers. Each of them can be used as two single-precision registers, providing a total of 32 single-precision registers. An odd–even number pair of double-precision registers can be used as a quad-precision register, thus allowing 8 quad-precision registers. SPARC Version 9 added 16 more double-precision registers, but these additional registers can not be accessed as single-precision registers. No SPARC CPU implements quad-precision operations in hardware as of 2024.
Tagged add and subtract instructions perform adds and subtracts on values checking that the bottom two bits of both operands are 0 and reporting overflow if they are not. This can be useful in the implementation of the run time for ML, Lisp, and similar languages that might use a tagged integer format.
The endianness of the 32-bit SPARC V8 architecture is purely big-endian. The 64-bit SPARC V9 architecture uses big-endian instructions, but can access data in either big-endian or little-endian byte order, chosen either at the application instruction level or at the memory page level. The latter is often used for accessing data from inherently little-endian devices, such as those on PCI buses.

History

v7 → v8 → v9 → JPS1 → JPS2 → UA2005 → UA2007 → OSA2011 → OSA2015 → OSA2017
There have been three major revisions of the architecture. The first published version was the 32-bit SPARC version 7 in 1986. SPARC version 8, an enhanced SPARC architecture definition, was released in 1990. The main differences between V7 and V8 were the addition of integer multiply and divide instructions, and an upgrade from 80-bit "extended-precision" floating-point arithmetic to 128-bit "quad-precision" arithmetic. SPARC V8 served as the basis for IEEE Standard 1754-1994, an IEEE standard for a 32-bit microprocessor architecture.
SPARC version 9, the 64-bit SPARC architecture, was released by SPARC International in 1993. It was developed by the SPARC Architecture Committee consisting of Amdahl Corporation, Fujitsu, ICL, LSI Logic, Matsushita, Philips, Ross Technology, Sun Microsystems, and Texas Instruments. Newer specifications always remain compliant with the full SPARC V9 Level 1 specification.
In 2002, the SPARC Joint Programming Specification 1 was released by Fujitsu and Sun, describing processor functions which were identically implemented in the CPUs of both companies. The first CPUs conforming to JPS1 were the UltraSPARC III by Sun and the SPARC64 V by Fujitsu. Functionalities which are not covered by JPS1 are documented for each processor in "Implementation Supplements".
At the end of 2003, Joint Programming Specification 2 was released to support multicore CPUs. The first CPUs conforming to JPS2 were the UltraSPARC IV by Sun and the SPARC64 VI by Fujitsu.
In early 2006, Sun released an extended architecture specification, UltraSPARC Architecture 2005. This includes not only the non-privileged and most of the privileged portions of SPARC V9, but also all the architectural extensions developed through the processor generations of UltraSPARC III, IV, and IV+, as well as Chip Multithreading Technology extensions starting with the UltraSPARC T1 implementation:

the VIS 1 and VIS 2 instruction set extensions and the associated GSR register
multiple levels of global registers, controlled by the GL register
Sun's 64-bit MMU architecture
privileged instructions ALLCLEAN, OTHERW, NORMALW, and INVALW
access to the VER register is now hyperprivileged
the SIR instruction is now hyperprivileged

In 2007, Sun released an updated specification, UltraSPARC Architecture 2007, to which the UltraSPARC T2 implementation complied.
In December 2007, Sun also made the UltraSPARC T2 processor's RTL available via the OpenSPARC project. It was also released under the GNU General public license v2. OpenSPARC T2 is 8 cores, 16 pipelines with 64 threads.
In August 2012, Oracle Corporation made available a new specification, Oracle SPARC Architecture 2011, which besides the overall update of the reference, adds the VIS 3 instruction set extensions and hyperprivileged mode to the 2007 specification.
In October 2015, Oracle released SPARC M7, the first processor based on the new Oracle SPARC Architecture 2015 specification. This revision includes VIS 4 instruction set extensions and hardware-assisted encryption and silicon secured memory.
In September 2017, Oracle released SPARC M8, the first processor based on the new Oracle SPARC Architecture 2017 specification.
SPARC architecture has provided continuous application binary compatibility from the first SPARC V7 implementation in 1987 through the Sun UltraSPARC Architecture implementations.
Among various implementations of SPARC, Sun's SuperSPARC and UltraSPARC-I were very popular, and were used as reference systems for SPEC CPU95 and CPU2000 benchmarks. The 296 MHz UltraSPARC-II is the reference system for the SPEC CPU2006 benchmark.