ARM processors Adam Hoover

ARM processors Family of 32-bit microcontroller processors ARM has changed their name several times: What is it? Who makes it? Acorn RISC Machines (1985) Advanced RISC Machines (1990) ARM Holdings (1998) Mid-high level complexity hand-held consumer electronics What is its niche? PDA’s (1980’s) Cell phones (1990’s) Handheld game devices (2000’s)

Example Consumer Products Gameboy advance Nintendo DS Apple Ipod Apple Iphone TASC ChessMachine Apple Newton PDA

Processor design, not a chip Nintendo DS Core design Chip design & fabrication ARM licenses core designs to other companies OEMs can customize chips ARM provides compilers, development tools, and debugging tools for chip development and product development

ARM chips (examples)

ARM processor features Small number of transistors (~35,000) No microcode, all instructions hard-wired (no flexibility in ISA) 3-stage pipeline (simple fetch-decode-execute) 4-8 KB cache memory, typically unified (data/instruction) 32-bit ISA (not used for simple control stuff) MHz clock speed ARM1 (1985) to ARM11 and Cortex lines, most having 5+ flavors ARM7 cores “Thumb” instruction set – 16 bit ISA packed into 32-bit code “Jazelle” instruction set – java code executed in hardware (instead of JVM) ARM extensions

ARM assembly code is dense C program code: while (i != j) { if (i > j) i -= j; else j -= i; } ARM assembly code: loop CMP Ri, Rj ; set condition "NE" if (i != j) ; "GT" if (i > j), or "LT" if (i < j) SUBGT Ri, Ri, Rj ; if "GT", i = i-j SUBLT Rj, Rj, Ri ; if "LT", j = j-I BNE loop ; if "NE", then loop multiple pieces of work per instruction

ARM chip pricing Core licensing – $200,000 to $10,000,000 depending Some chip examples: Atmel AT91SAM family -- $3/unit qty 10,000 (2005) NXP LPC24xx family -- $8-14/unit qty 1 (2009) Texas Instruments MS470 family - $10-22/unit qty 1 (2009) For further pricing, check For further information, see