Jonah Probell
EE Times(10/26/2009 12:01 AM EDT)
ISA in PCs is due to Microsoft Windows' exclusive support. MIPS lost a great opportunity when Microsoft dropped MIPS support from early versions of Windows NT.
ARM's success in mobile phones is due largely to Symbian's mid-1990s decision to support only the ARM ISA--a move that was itself the result of a decision by Texas Instruments to use ARM in mobile phone ASICs for Nokia, then the dominant handset maker. At the time, MIPS was part of Silicon Graphics. MIPS spun out after Symbian came to dominate the phone OS market and lacked incentive to support another ISA.
Aside from cost, power consumption is the largest factor in handset makers' chip vendor choices. People have asserted, without compelling data, that the ARM ISA inherently yields lower-power chips than other ISAs. Actually, fab technology is the biggest factor in power consumption. Microarchitecture--the pipeline depth and instruction-level parallelism--is next, followed by EDA methodology. The ISA has a negligible impact on power consumption. ARM's dominance in handsets is due to historical business decisions, not its ISA.