SPARC

Features

The SPARC architecture was heavily influenced by the earlier RISC designs including the 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 (one of which, g0, is hard-wired to zero, so only seven of them are usable as 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 8 local registers and shares 8 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 (non-privileged) 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 (addressing and data) 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 (which can also be accessed as 8 quad 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 2004.

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 (load/store) level or at the memory page level (via an MMU setting). The latter is often used for accessing data from inherently little-endian devices, such as those on PCI buses.

History

There have been three major revisions of the architecture. The first published revision was the 32-bit SPARC Version 7 (V7) in 1986. SPARC Version 8 (V8), 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 (JPS1) was released by Fujitsu and Sun, describing processor functions which were identically implemented in the CPUs of both companies ("Commonality"). 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, JPS2 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, IV+ as well as CMT extensions starting with the UltraSPARC T1 implementation:

In 2007, Sun released an updated specification, UltraSPARC Architecture 2007, to which the UltraSPARC T2 implementation complied.

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.

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.

SPARC architecture licensees

The following organizations have licensed the SPARC architecture:

Implementations

Notes:

Operating system support

SPARC machines have generally used Sun's SunOS, Solaris, OpenSolaris or derived as Illumos, but other operating systems such as NeXTSTEP, RTEMS, FreeBSD, OpenBSD, NetBSD, and Linux have also been used.

In 1993, Intergraph announced a port of Windows NT to the SPARC architecture, but it was later cancelled.

In October 2015, Oracle announced a "Linux for SPARC reference platform".

Open source implementations

Several fully open source implementations of the SPARC architecture exist:

A fully open source simulator for the SPARC architecture also exists:

Supercomputers

For HPC loads Fujitsu builds specialized SPARC64 fx processors with a new instruction extensions set called HPC-ACE (High Performance Computing – Arithmetic Computational Extensions).

Fujitsu's K computer ranked #1 in TOP500 – June 2011 and November 2011 lists. It combines 88,128 SPARC64 VIIIfx CPUs, each with eight cores, for a total of 705,024 cores – almost twice as many as any other system in the TOP500 at that time. The K Computer was more powerful than the next five systems on the list combined, and had the highest performance-to-power ratio of any other supercomputer system. It also ranked #6 in Green500 – June 2011 list, with a score of 824.56 MFLOPS/W. In the November 2012 release of TOP500, the K computer ranked #3, using by far the most power of the top three. It ranked #85 on the corresponding Green500 release. Newer HPC processors, IXfx and XIfx, were included in recent PRIMEHPC FX10 and FX100 supercomputers.

Tianhe-2 (TOP500 #1 as of November 2014) has a number of nodes with Galaxy FT-1500 OpenSPARC-based processors developed in China. However, those processors did not contribute to the LINPACK score.