- Comparison of CPU architectures
Computer architectures are often described as n-bit architectures. Today n is often 8, 16, 32, or 64, but other sizes have been used. This is actually a strong simplification. A computer architecture often has a few more or less "natural" datasizes in the instruction set, but the hardware implementation of these may be very different. Many architectures have instructions operating on half and/or twice the size of respective processors major internal datapaths. Examples of this are the 8080, Z80, MC68000 as well as many others. On this type of implementations, a twice as wide operation typically also takes around twice as many clock cycles (which is not the case on high performance implementations). On the 68000, for instance, this means 8 instead of 4 clock ticks, and this particular chip may be described as a 32-bit architecture with a 16-bit implementation. The external databus width is often not useful to determine the width of the architecture; the NS32008, NS32016 and NS32032 were basically the same 32-bit chip with different external data buses. The NS32764 had a 64-bit bus, but used 32-bit registers.
The width of addresses may or may not be different than the width of data. Early 32-bit microprocessors often had a 24-bit address, as did the System/360 processors.
The number of operands is one of the factors that may give an indication about the performance of the instruction set. A three-operand architecture will allow
A := B + C
to be computed in one instruction.
A two-operand architecture will allow
A := A + B
to be computed in one instruction, so two instructions will need to be executed to simulate a single three-operand instruction
A := B A := A + C
An architecture may use "big" or "little" endianness, or both, or be configurable to use either. Little endian processors order bytes in memory with the least significant byte of a multi-byte value in the lowest-numbered memory location. Big endian architectures instead order them with the most significant byte at the lowest-numbered address. The x86 and the ARM architectures as well as several 8-bit architectures are little endian. Most RISC architectures (SPARC, Power, PowerPC, MIPS) were originally big endian, but many (including ARM) are now configurable.
The table below compares basic information about CPU architectures.
Architecture Bits Version Introduced Max # Operands Type Design Registers Instruction encoding Branch Evaluation Endianness Extensions Open Royalty-free Alpha 64 1992 3 Register-Register RISC 32 Fixed Condition register Bi , , , No Unknown ARM 32 ARMv7 and earlier 1983 3 Register-Register RISC 16 Fixed (32-bit), Thumb: Fixed (16-bit), Thumb-2: Variable (16 and 32-bit) Condition code Bi NEON, Jazelle, TrustZone, Unknown No ARM 64 ARMv8 TBA 3 Register-Register RISC 30 Fixed (32-bit), Thumb: Fixed (16-bit), Thumb-2: Variable (16 and 32-bit), A64 Condition code Bi NEON, Jazelle, TrustZone, Unknown No AVR32 32 Rev 2 2006 2-3 RISC 15 Variable Big Java Virtual Machine Unknown Unknown Blackfin 32 2000 RISC 8 Little Unknown Unknown DLX 32 1990 3 RISC 32 Fixed (32-bit) Big Unknown Unknown eSi-RISC 16/32 2009 3 Register-Register RISC 8-72 Variable(16 or 32-bit) Compare and branch and condition register Bi User-defined instructions No No Itanium (IA-64) 64 2001 Register-Register EPIC 128 Condition register Bi (selectable) Intel Virtualization Technology Yes Yes M32R 32 1997 RISC 16 Fixed (16- or 32-bit) Bi Unknown Unknown m68k 16/32 1979 CISC 16 Big Unknown Unknown Mico32 32 2006 3 Register-Register RISC 32 Fixed (32-bit) Compare and branch Big User-defined instructions Yes Yes MIPS 64 (32→64) 5 1981 3 Register-Register RISC 32 Fixed (32-bit) Condition register Bi MDMX, MIPS-3D Unknown No MMIX 64 1999 3 Register-Register RISC 256 Fixed (32-bit) Big Yes Yes PA-RISC (HP/PA) 64 (32→64) 2.0 1986 3 RISC 32 Fixed Compare and branch Big Multimedia Acceleration eXtensions (MAX), MAX-2 No Unknown PowerPC 32/64 (32→64) 2.06 1991 3 Register-Register RISC 32 Fixed, Variable Condition code Big/Bi AltiVec, APU, VSX, Cell Yes No S+core 32/16-bit 2005 RISC Little Unknown Unknown Series 32000 32 1982 5 Memory-Memory CISC 8 Variable Huffman coded, up to 23 bytes long Condition Code Little BitBlt instructions Unknown Unknown SPARC 64 (32→64) V9 1985 3 Register-Register RISC 32 Fixed Condition code Big → Bi VIS 1.0, 2.0, 3.0 Yes Yes SuperH (SH) 32 1990s 2 Register-Register/ Register-Memory RISC 16 Fixed Condition Code (Single Bit) Bi Unknown Unknown System/360 / System/370 / z/Architecture 64 (32→64) 3 1964 Register-Memory/Memory-Memory CISC 16 Fixed Condition code Big Unknown Unknown VAX 32 1977 6 Memory-Memory CISC 16 Variable Compare and branch Little VAX Vector Architecture Unknown Unknown x86 64 (16→32→64) 1978 2 Register-Memory CISC 8 (x86-64 has 16) Variable Condition code Little MMX, 3DNow! SSE, PAE, x86-64, AVX No No
The following table compares specific microarchitectures.
Microarchitecture Pipeline stages Misc AMD K5 Out-of-order execution, register renaming, speculative execution AMD K6 Superscalar, branch prediction AMD K6-III Branch prediction, speculative execution, out-of-order execution AMD K7 Out-of-order execution, branch prediction, Harvard architecture AMD K8 64-bit, integrated memory controller, 16 byte instruction prefetching AMD K10 Superscalar, out-of-order execution, 32-way set associative L3 victim cache, 32-byte instruction prefetching ARM7TDMI(-S) 3 ARM7EJ-S 5 ARM810 5 ARM9TDMI 5 ARM1020E 6 XScale PXA210/PXA250 7 ARM1136J(F)-S 8 ARM1156T2(F)-S 9 ARM Cortex-A5 8 ARM Cortex-A8 13 ARM Cortex-A9 Out-of-order, speculative issue, superscalar ARM Cortex-A15 Multicore (up to 16) AVR32 AP7 7 AVR32 UC3 3 Harvard architecture Bobcat Out-of-order execution Bulldozer Shared L3 cache, multithreading, multicore, integrated memory controller Crusoe In-order execution, 128-bit VLIW, integrated memory controller Efficeon In-order execution, 256-bit VLIW, fully integrated memory controller Cyrix Cx5x86 6 Branch prediction Cyrix 6x86 Superscalar, superpipelined, register renaming, speculative execution, out-of-order execution DLX 5 EV4 (Alpha 21064) Superscalar EV7 (Alpha 21364) Superscalar design with out-of-order execution, branch prediction, 4-way SMT, integrated memory controller EV8 (Alpha 21464) Superscalar design with out-of-order execution P5 (Pentium) 5 Superscalar P6 (Pentium Pro) 14 Speculative execution, Register renaming, superscalar design with out-of-order execution P6 (Pentium II) Branch prediction P6 (Pentium III) 10 Itanium Speculative execution, branch prediction, register renaming, 30 execution units, multithreading NetBurst (Willamette) 20 Simultaneous multithreading NetBurst (Northwood) 20 Simultaneous multithreading NetBurst (Prescott) 31 Simultaneous multithreading NetBurst (Cedar Mill) 31 Simultaneous multithreading Core 14 Intel Atom 16 Simultaneous multithreading, in-order. No instruction reordering, speculative execution, or register renaming. Nehalem Simultaneous multithreading, integrated memory controller, L1/L2/L3 cache Sandy Bridge Simultaneous multithreading, multicore, integrated memory controller, L1/L2/L3 cache. 2 threads per core. Haswell 14 Multicore LatticeMico32 6 Harvard architecture POWER1 Supescalar, out-of-order execution POWER3 Supescalar, out-of-order execution POWER4 Supescalar, speculative execution, out-of-order execution POWER5 Simultaneous multithreading, out-of-order execution, integrated memory controller POWER6 2-way simultaneous multithreading, in-order execution POWER7 4 SMT threads per core, 12 execution units per core 401PowerPC 401 3 PowerPC 405 5 PowerPC 440 7 PowerPC 470 9 SMP PowerPC A2 15 PowerPC e300 4 Superscalar, Branch prediction PowerPC e500 Dual 7 stage Multicore PowerPC e600 3-issue 7 stage Superscalar out-of-order execution, branch prediction PowerPC e5500 4-issue 7 stage Out-of-order, multicore PowerPC 603 4 5 execution units, branch prediction. No SMP. PowerPC 603q 5 In-order PowerPC 604 6 Superscalar, out-of-order execution, 6 execution units. SMP support. PowerPC 620 5 Out-of-order execution- SMP support. PWRficient Superscalar, out-of-order execution, 6 execution units R4000 8 Scalar StrongARM SA-110 5 Scalar, in-order SuperH SH2 5 SuperH SH2A 5 Superscalar, Harvard architecture SPARC Superscalar HyperSPARC Superscalar SuperSPARC Superscalar, in-order SPARC64 VI/VII/VII+ Superscalar, out-of-order UltraSPARC 9 UltraSPARC T1 6 Open source, multithreading, multi-core, 4 threads per core, integrated memory controller UltraSPARC T2 8 Open source, multithreading, multi-core, 8 threads per core SPARC T3 Multithreading, multi-core, 8 threads per core, SMP SPARC T4 Multithreading, multi-core, 8 threads per core, SMP, out-of-order VIA C7 In-order execution VIA Nano (Isaiah) Superscalar out-of-order execution, branch prediction, 7 execution units WinChip 4 In-order execution
- Central processing unit (CPU)
- CPU design
- Instruction set
- List of instruction sets
- Benchmark (computing)
- ^ ARMv8 Technology Preview
- ^ "AVR32 Architecture Document". Atmel. http://www.atmel.com/dyn/resources/prod_documents/doc32000.pdf. Retrieved 2008-06-15.
- ^ "Blackfin Processor Architecture Overview". Analog Devices. http://www.analog.com/en/embedded-processing-dsp/blackfin/content/blackfin_architecture/fca.html. Retrieved 2009-05-10.
- ^ "Blackfin memory architecture". Analog Devices. http://www.analog.com/FAQs/FAQDisplay.html?DSPKBContentID=752A11D1-9E11-4A7F-91AC-CA3C264C5667. Retrieved 2009-12-18.
- ^ "LatticeMico32 Architecture". Lattice Semiconductor. http://www.latticesemi.com/products/intellectualproperty/ipcores/mico32/mico32architecture.cfm. Retrieved 2009-12-18.
- ^ "Open Source Licensing". Lattice Semiconductor. http://www.latticesemi.com/products/intellectualproperty/ipcores/mico32/mico32opensourcelicensing.cfm. Retrieved 2009-12-18.
- ^ "Power ISA V2.06". IBM. http://www.power.org/resources/downloads/PowerISA_V2.06_PUBLIC.pdf. Retrieved 2009-07-04. [dead link]
- ^ http://www.ibm.com/developerworks/power/newto/#2 New to Cell/B.E., multicore, and Power Architecture technology
- ^ http://www.sparc.org/specificationsDocuments.html##ArchLic SPARC Architecture License
- ^ http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_1260_1288%5E1295,00.html
- ^ http://www.pcguide.com/ref/cpu/fam/g4C5x86-c.html
- ^ http://www.fujitsu.com/global/services/computing/server/sparcenterprise/technology/performance/processor.html
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