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The early [[MIPS]] architectures were 32-bit implementations (generally 32-bit wide registers and data paths), while later versions were 64-bit implementations. Five backward-compatible revisions of the MIPS instruction set exist, named <tt>MIPS I</tt>, <tt>MIPS II</tt>, <tt>MIPS III</tt>, <tt>MIPS IV</tt>, and <tt>MIPS 32/64</tt>. The latest of these, <tt>MIPS 32/64</tt> Release 2, defines a control register set as well as the instruction set. Several "add-on" extensions are also available, including <tt>MIPS-3D</tt> which is a simple set of floating-point SIMD instructions dedicated to common 3D tasks, <tt>MDMX(MaDMaX)</tt> which is a more extensive integer SIMD instruction set using the 64-bit floating-point registers, <tt>MIPS16</tt> which adds compression to the instruction stream to make programs take up less room (allegedly a response to the ARM architecture encoding in the ARM architecture), and the recent addition of <tt>MIPS MT</tt>, new multithreading additions to the system similar to HyperThreading in the Intel's Pentium 4 processors.
 
The early [[MIPS]] architectures were 32-bit implementations (generally 32-bit wide registers and data paths), while later versions were 64-bit implementations. Five backward-compatible revisions of the MIPS instruction set exist, named <tt>MIPS I</tt>, <tt>MIPS II</tt>, <tt>MIPS III</tt>, <tt>MIPS IV</tt>, and <tt>MIPS 32/64</tt>. The latest of these, <tt>MIPS 32/64</tt> Release 2, defines a control register set as well as the instruction set. Several "add-on" extensions are also available, including <tt>MIPS-3D</tt> which is a simple set of floating-point SIMD instructions dedicated to common 3D tasks, <tt>MDMX(MaDMaX)</tt> which is a more extensive integer SIMD instruction set using the 64-bit floating-point registers, <tt>MIPS16</tt> which adds compression to the instruction stream to make programs take up less room (allegedly a response to the ARM architecture encoding in the ARM architecture), and the recent addition of <tt>MIPS MT</tt>, new multithreading additions to the system similar to HyperThreading in the Intel's Pentium 4 processors.
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Because the designers created such a [[#Summary of R3000 instruction set|clean instruction set]], computer architecture courses in universities and technical schools often study the MIPS architecture. The design of the [[MIPS]] CPU family greatly influenced later RISC architectures such as DEC Alpha.
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Because the designers created such a [[#Summary of R3000 instruction set|clean instruction set]], computer architecture courses in universities and technical schools often study the MIPS architecture. The design of the [[MIPS]] CPU family greatly influenced later RISC architectures such as [[DEC Alpha]].
    
==History==
 
==History==
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== Applications ==
 
== Applications ==
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Among the manufacturers which made computer workstation systems using MIPS processors are Silicon Graphics|SGI, MIPS Computer Systems, Inc., Olivetti, Siemens Nixdorf Informationssysteme|Siemens-Nixdorf, Acer (company)|Acer, Digital Equipment Corporation, NEC Corporation|NEC, and DeskStation. Various operating systems have been ported to the architecture, such as SGI's IRIX, Microsoft's Windows NT (although support for MIPS ended with the release of Windows NT 4.0) and Windows CE, Linux, BSD, Unix|UNIX System V, SINIX, MIPS Computer Systems' own RISC/os, and others.
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Among the manufacturers which made computer workstation systems using MIPS processors are [[Silicon Graphics]]|SGI, MIPS Computer Systems, Inc., Olivetti, Siemens Nixdorf Informationssysteme|Siemens-Nixdorf, Acer (company)|Acer, Digital Equipment Corporation, NEC Corporation|NEC, and DeskStation. Various operating systems have been ported to the architecture, such as SGI's [[IRIX]], Microsoft's Windows NT (although support for MIPS ended with the release of [[Windows NT 4.0]]) and Windows CE, Linux, BSD, Unix|UNIX System V, SINIX, MIPS Computer Systems' own RISC/os, and others.
    
However, use of MIPS as the main processor of computer workstations has declined, and SGI has announced its plans to cease developing high-performance iterations of the MIPS architecture in favor of using Intel IA64-based processors (see "Other models and future plans" section below).
 
However, use of MIPS as the main processor of computer workstations has declined, and SGI has announced its plans to cease developing high-performance iterations of the MIPS architecture in favor of using Intel IA64-based processors (see "Other models and future plans" section below).
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The R18000 improved the floating-point instruction queues and revised the floating-point unit to feature two multiply-add units, quadrupling the peak FLOPS count. Division and square-root were performed in separate non-pipelined units in parallel to the multiply-add units. The system interface and memory hierarchy was also significantly reworked. It would have a 52-bit virtual address and a 48-bit physical address. The bidirectional multiplexed address and data system bus of the R18000 would be replaced by two unidirectional DDR links, a 64-bit multiplexed address and write path and a 128-bit read path. Although they are unidirectional, each path could be shared by another R18000, although the two would be shared through multiplexing. The bus could also be configured in the SysAD or Avalanche configuration for backwards compatibility with R10000 systems.
 
The R18000 improved the floating-point instruction queues and revised the floating-point unit to feature two multiply-add units, quadrupling the peak FLOPS count. Division and square-root were performed in separate non-pipelined units in parallel to the multiply-add units. The system interface and memory hierarchy was also significantly reworked. It would have a 52-bit virtual address and a 48-bit physical address. The bidirectional multiplexed address and data system bus of the R18000 would be replaced by two unidirectional DDR links, a 64-bit multiplexed address and write path and a 128-bit read path. Although they are unidirectional, each path could be shared by another R18000, although the two would be shared through multiplexing. The bus could also be configured in the SysAD or Avalanche configuration for backwards compatibility with R10000 systems.
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The R18000 would have a 1&nbsp;MB four-way set-associative secondary cache would be included on-die; supplemented by an optional tertiary cache built from single data rate (SDR) or double data rate (DDR) SSRAM or DDR SDRAM with capacities of 2 to 64&nbsp;MB. The L3 cache had its cache tags, equivalent to 400&nbsp;KB, located on-die to reduce latency. The L3 cache is accessed via a 144-bit bus, of which 128 bits are for data and 8 bit for ECC. The L3 cache's clock rate was to have been programmable.
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The R18000 would have a 1&nbsp;MB four-way set-associative secondary cache would be included on-die; supplemented by an optional tertiary cache built from single data rate (SDR) or double data rate ([[DDR]]) SSRAM or DDR [[SDRAM]] with capacities of 2 to 64&nbsp;MB. The L3 cache had its cache tags, equivalent to 400&nbsp;KB, located on-die to reduce latency. The L3 cache is accessed via a 144-bit bus, of which 128 bits are for data and 8 bit for ECC. The L3 cache's clock rate was to have been programmable.
    
The R18000 was to be fabricated in NEC's UX5 process, a 0.13&nbsp;µm CMOS process with nine levels of copper interconnect. It would have used 1.2&nbsp;V power supply and dissipated less heat than contemporary server microprocessors in order to be densely packed into systems.
 
The R18000 was to be fabricated in NEC's UX5 process, a 0.13&nbsp;µm CMOS process with nine levels of copper interconnect. It would have used 1.2&nbsp;V power supply and dissipated less heat than contemporary server microprocessors in order to be densely packed into systems.
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[[Category:SGI]][[Category:Computing]]
 
[[Category:SGI]][[Category:Computing]]
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[[Category:Processors]]
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[[Category:MIPS]]