SPARC (Scalable Processor ARChitecture) is a pure big-endian RISC microprocessor instruction set architecture originally designed in 1985 by Sun Microsystems. SPARC is a registered trademark of SPARC International, Inc., an organization established in 1989 to promote the SPARC and to provide conformance testing. SPARC International was intended to "open" the SPARC architecture to make a larger ecosystem for the design, which has been licensed to several manufacturers, including Texas Instruments, Cypress Semiconductor, and Fujitsu. As a result of SPARC International, the SPARC architecture is fully open and non-proprietary.
In fact, there are two fully open source implementations available. The source code (written in VHDL) of a 32-bit, single-thread SPARC Version 8 implementation called LEON is available under the LGPL. A 64-bit, 32-thread implementation that conforms to the UltraSPARC Architecture 2005 and to SPARC Version 9, called OpenSPARC T1, is also available under an open source license. The OpenSPARC T1 implementation is written in Verilog.
Implementations of the SPARC architecture were initially designed and used for workstations, and then used for larger SMP servers produced by Sun Microsystems and Fujitsu, among others. SPARC machines are generally synonymous with Solaris, the operating system (OS) from Sun designed for SPARC. However, operating systems such as NeXTSTEP, Linux, FreeBSD, OpenBSD and NetBSD have been ported to systems that use SPARC processors.
There have been several revisions of the architecture. SPARC Version 8, considered the standard 32-bit SPARC architecture definition, was released in the late 1980s. SPARC Version 9, the 64-bit SPARC architecture, was released by SPARC International in 1994. In early 2006, Sun released an extended architecture specification, UltraSPARC Architecture 2005. UltraSPARC Architecture 2005 includes not only the nonprivileged and most of the privileged portions of SPARC V9, but also all the architectural extensions (such as CMT, hyperprivileged, VIS 1, and VIS 2) present in Sun's UltraSPARC processors starting with the UltraSPARC T1 implementation.
As of December 2005 Sun announced their UltraSPARC T1 design would be open sourced, and in March 2006 the full source code became available (see OpenSPARC).
The SPARC architecture was heavily influenced by the earlier designs of the RISC I & II from the University of California, Berkeley. 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 128 general purpose registers. At any point, only 32 of them are immediately visible to software - 8 are global registers (one of which, g0, is hard-wired to zero, so only 7 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 (nonprivileged) instruction set. One of the architectural parameters that can scale is the number of implemented register windows; the specification allows from 3 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 3 to reduce context switching time, or to implement some number between them. Other architectures that include similar register windows include Intel i960, IA-64, and AMD 29000.
In SPARC version 8 (1987), 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 (1995) 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.
Tagged add and subtract instructions perform adds and subtracts on values assuming that the bottom two bits do not participate in the computation. 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 architecture has gone through a few revisions. It gained hardware multiply and divide functionality in version 8. The most substantial upgrade resulted in version 9, which is a 64-bit (addressing and data) SPARC specification.
A Sun-specific architecture specification, UltraSPARC Architecture 2005, added specification of additional instructions, registers, and hyperprivileged mode -- all of which had became standard in UltraSPARC processors starting with the UltraSPARC T1 8-core, 32-thread implementation. UltraSPARC Architecture 2005 includes Sun's standard extensions and remains compliant with the full SPARC V9 Level 1 specification. The architecture has provided continuous application binary compatibility from the first SPARC V7 implementation in 1987 into the Sun UltraSPARC Architecture implementations.
Sun open-sourced the UltraSPARC T1 implementation in December 2005; see OpenSPARC.
Among various implementations of SPARC, Sun's SuperSPARC and UltraSPARC-I were very popular, so as to be used as reference systems for SPEC CPU95 and CPU2000 benchmarks.
| Model | Frequency * | Architecture Version | Year | Threads Per Core * Cores = Total Threads | Process * | Transistors * | Die size * | IO Pins | Power * | Voltage * | L1 Dcache * | L1 Icache * | L2 Cache * | L3 Cache * |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| microSPARC I | 40–50 | V8 | 1992 | 1*1=1 | 0.8 | 0.8 | 225? | 288 | 2.5 | 5 | 2 | 4 | none | none |
| SuperSPARC I | 33–60 | V8 | 1992 | 1*1=1 | 0.8 | 3.1 | -- | 293 | 14.3 | 5 | 16 | 20 | 0-2048 | none |
| HyperSPARC A | 40–90 | V8 | 1993 | 1*1=1 | 0.5 | 1.5 | -- | -- | -- | 5? | 8 | 128-256 | none | |
| microSPARC II | 60–125 | V8 | 1994 | 1*1=1 | 0.5 | 2.3 | 233 | 321 | 5 | 3.3 | 8 | 16 | none | none |
| HyperSPARC B | 90–125 | V8 | 1994 | 1*1=1 | 0.4 | 1.5 | -- | -- | -- | 3.3 | 8 | 128-256 | none | |
| SuperSPARC II | 75–90 | V8 | 1994 | 1*1=1 | 0.8 | 3.1 | 299 | -- | 16 | -- | 16 | 20 | 1024-2048 | none |
| HyperSPARC C | 125–166 | V8 | 1995 | 1*1=1 | 0.35 | 1.5 | -- | -- | -- | 3.3 | 8 | 512-1024 | none | |
| TurboSPARC | 160–180 | V8 | 1995 | 1*1=1 | 0.35 | 3.0 | 132 | 416 | 7 | 3.5 | 16 | 16 | 512 | none |
| UltraSPARC I (Spitfire) | 143–167 | V9 | 1995 | 1*1=1 | 0.47 | 5.2 | 315 | 521 | 30 @167 MHz | 3.3 | 16 | 16 | 512-1024 | none |
| UltraSPARC I (Hornet) | 200 | V9 | 1998 | 1*1=1 | 0.42 | 5.2 | 265 | 521 | -- | 3.3 | 16 | 16 | 512-1024 | none |
| HyperSPARC D | 180–200 | V8 | 1996 | 1*1=1 | 0.35 | 1.7 | -- | -- | -- | 3.3 | 16 | 16 | 512 | none |
| UltraSPARC IIs (Blackbird) | 250–400 | V9 | 1997 | 1*1=1 | 0.35 | 5.4 | 149 | 521 | 25 @250 MHz | 2.5 | 16 | 16 | 1024 or 4096 | none |
| UltraSPARC IIs (Sapphire-Black) | 360–480 | V9 | 1999 | 1*1=1 | 0.25 | 5.4 | 126 | 521 | 21 @400 MHz | 1.9 | 16 | 16 | 1024–8192 | none |
| UltraSPARC IIi (Sabre) | 270–360 | V9 | 1997 | 1*1=1 | 0.35 | 5.4 | 156 | 587 | 21 | 1.9 | 16 | 16 | 256–2048 | none |
| UltraSPARC IIi (Sapphire-Red) | 333–480 | V9 | 1998 | 1*1=1 | 0.25 | 5.4 | -- | 587 | 21 @440 MHz | 1.9 | 16 | 16 | 2048 | none |
| UltraSPARC IIe (Hummingbird) | 400–600 | V9 | 2000 | 1*1=1 | 0.18 Al | -- | -- | 370 | 13 max @500 MHz | 1.5-1.7 | 16 | 16 | 256 | none |
| UltraSPARC IIi (IIe+) | 550–650 | V9 | 2002 | 1*1=1 | 0.18 Cu | -- | -- | 370 | 17.6 | 1.7 | 16 | 16 | 512 | none |
| UltraSPARC III (Cheetah) | 600 | V9 | 2001 | 1*1=1 | 0.18 Al | 29 | 330 | 1368 | 53 | 1.6 | 64 | 32 | 8192 | none |
| UltraSPARC III (Cheetah) | 750–900 | V9 | 2001 | 1*1=1 | 0.13 Al | 29 | -- | 1368 | -- | 1.6 | 64 | 32 | 8192 | none |
| UltraSPARC IIIcu (Cheetah+) | 1002–1200 | V9 | 2001 | 1*1=1 | 0.13 Cu | 29 | -- | 1368 | -- | 1.6 | 64 | 32 | 8192 | none |
| UltraSPARC IIIi (Jalepeno) | 1064–1593 | V9 | 2003 | 1*1=1 | 0.13 | 87.5 | 206 | 959 | 52 | 1.3 | 64 | 32 | 1024 | none |
| UltraSPARC IV (Jaguar) | 1050–1350 | V9 | 2004 | 1*2=2 | 0.13 | 66 | 356 | 1368 | 108 | 1.35 | 64 | 32 | 16384 | none |
| UltraSPARC IV+ (Panther) | 1500 | V9 | 2005 | 1*2=2 | 0.09 | 295 | 336 | 1368 | 90 | 1.1 | 64 | 64 | 2048 | 32768 |
| UltraSPARC T1 (Niagara) | 1000–1200 | V9 / UA 2005 | 2005 | 4*8=32 | 0.09 | 300 | 380 | 1933 | 72 | 1.3 | 8 | 16 | 3072 | none |
SPARC64™ V is a processor family developed by Fujitsu and used in their PRIMEPOWER family of servers.
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