TheARM Architecture Thomas DeMeo Thomas Becker Agenda • What is ARM? • ARM History • ARM Design Objectives • ARM Architectures What is the ARM Architecture? • Advanced RISC Machines • ARM is a 32-bit RISC ISA • Most popular 32-bit ISA on the market • Found in nearly every kind of consumer electronic: o 90% of all embedded 32-bit RISC processors o 98% of all cell phones o Hard drives, routers, phones, tablets, handheld video game consoles, calculators, and more • Recently introduced 64-bit architecture and ISA, labelled 'AArch64' or 'A64' A Bit of History... • A company named Acorn Computers had released the BBC Micro in 1981 • The Micro used the 6502 • Became very popular in the British educational system • Soon dominated by the IBM PC Acorn's next steps • Acorn was focused on meeting the needs of the business community, and this meant they needed more power. • After trying all of the 16 and 32-bit processors on the market they found none to be satisfactory for their purposes. The data bandwidth was not sufficiently greater than the current 8-bit 6502. • They decided to go solo. Acorn's next steps • So Acorn decided to make their own. • Inspired by the Berkeley RISC Project, which was the basis of the SPARC processor, Acorn figured that if some graduate students could build a 32-bit processor, so could they. • In 1983, the Acorn RISC Machine project had been established. Acorn's next steps • The 32-bit world • Reputable R&D department A Bit of History ARM first reached silicon in 1985, and worked just as intended. However, the architecture didn't make it into the commercial domain until 1987. The delay was caused by problems in design and production of an ARM-based system, and not in the chip itself. Acorn's financial woes at the time also contributed to this. Advanced RISC Machine • ARM was founded as a joint venture between Acorn Computers, Apple Computer, and VLSI Technology. • The company was intended to further the development of the Acorn RISC Machine's RISC Chip Apple Newton Project next to Apple iPhone Advanced RISC Machine • Early 1990's financially stable. Static processor version, ARM2aS. • Interest in ARM design leads to the formation of ARM Holdings as we know today. • ARM began licensing its designs to chip foundries, where they would receive a royalty ARM Design Objectives • Designed as a small scale processor • Good all-around performance • Fixed instruction length, load/store model • BASIC led to quick prototyping, but was less flexible when it came to hardware design ARM Design Objectives • Short design time • Easily customized designs ARM Design Objectives High Performance, Low Price, Low Power Consumption • Designed for price-to-performance ratio, not for being the most powerful o A6 cost approximately $1 per 1 MIPS • Relatively Low Transistor Count o ARM2 had 30K transistors o ARM6 had 35K transistors o ARM7 had 74K transistors o ARM9 had 111K transistors The ARM Architecture • Created by Sophie Wilson • General RISC design • Additional features o conditional instruction execution o interrupt subsystem o powerful indexed addressing modes o 2-priority level interrupt subsystem o 32-bit Barrel Shifter • 37 registers o 30 general purpose o Program Counter ARM Architecture CPU Modes • User • System (ARMv4 and above) • Monitor (security extensions only) • Supervisor • Abort • Undefined • IRQ - Interrupt Request ARM Architecture Versions • ARMv1 • ARMv2 • ARMv3 • ARMv4 • ARMv5 • ARMv6 • ARMv7 • ARMv8 o adds 64-bit architecture o newer exception system The Thumb Instruction Set • Improve code density • 16-bit instructions • Implicit instructions and limited functionality • Useful with size limitations • Thumb-2 (2003) added 32-bit instructions ARM Numbering • ARM Holdings adopted a new numbering scheme • Single number represents the processor core macrocell, main component, ARM6 • Incremented from generation to generation • Two-digit number represents self-contained chip, ARM60 • Three-digit number integrates the processor macrocell and other ARM macrocells and logic, ARM250 ARM7 • ARMv3, ARMv4, and ARMv5 architectures • Introduced the Thumb instruction set • 130 MIPS on 130 nm technology • Still quite popular Examples of ARM7 products • Nintendo Game Boy Advance • Nintendo DS • LEGO Mindstorms NXT • Apple iPod • Roomba • Sirius Satellite Radio receiver • Most vehicles ARM9 • ARMv4 and later ARMv5 architecture • First ARM processor to move from Von Neumann architecture to Harvard architecture • Decreased heat and power consumption compared to ARM7 • Pipeline was changed from 3 stages to 5 Examples of ARM9 products • Nintendo DS • PSP • Nintendo Wii • Nokia N-Gage • Western Digital MyBook external hard drives • Canon EOS 5D Mark II ARM11 • ARMv6 architecture • Decreased heat and power consumption compared to ARM9 • SIMD instructions for increased media support • Physically addressed cache • Redesigned pipeline allowing for faster clock Examples of ARM11 products • Nintendo 3DS • iPhone • iPod Touch • Zune HD • Samsung Galaxy • Kindle 2 • Raspberry Pi Current ARM Profiles Cortex-A • "Application" Cortex-R • "Real-Time" Cortex-M • "Microcontroller" Future • Cortex A15 MP o Out-of-order speculative superscalar design o Supports up to 2 clusters with up to 4 cores per cluster o Dual Core o Late 2012 o 5X performance of current smartphones o Addressing for up to 1TB of RAM o Tegra 4, 10X Tegra 2 • Quad core slated for 2013 Questions?.