Intel Corp (INTC)

[chipguy]

The core power cost of x86 over RISC depends on issue width,
pipeline depth, and in-order vs OOOE. The front end decoder
complexity goes up with the square of issue width for x86 vs
roughly linear for RISC. OOOE is also more complex for x86
than RISC. For something like C2D/Nehalem/SB x86 probably
adds 25-30% in power over an equivalent RISC. For something
like Atom it probably adds 15-20% in power over an equivalent
RISC.

Now keep in mind for a 1W phone SoC the CPU core accounts
for 300-400 mW. So x86 adds 45 - 80 mW in full active power
when EVERYTHING ELSE IS EQUAL. Please note the qualifier.
It is generally not true. In fact it is so not true that despite all
its baggage x86 accounts for over 90 cents out of every dollar
spent in the world on microprocessors of all size, description,
and use.