NEON's registers are 64-bit wide, so while I may issue a vaddq_f32 instruction (which performs its operation on 4x32-bit floats) it does the addition 64 bits at a time not 128 bits like true 128-bit SIMD untis -like AltiVec or SSE- do. The benchmark results seem quite logical actually.

The Registers are 128 Bits (Q Registers) wide but may be handled as 64 Bit Registers (D Registers) as well.

see:
http://infocenter.arm.com/help/index.js ... 03s02.html

The 128 Bit Q Registers can hold 2x 64 Bit, 4x32 Bit, 8x16 Bit or 16x8 Bit elements.

Also see:
http://infocenter.arm.com/help/index.js ... IIFHA.html

Here it performs 8x16 Bit integer add.
I guess this also works with 4x32 Bit float.


Or:
http://infocenter.arm.com/help/index.js ... 03s03.html

I did not verify the above with tests so far.
So of course I may misinterpret the docs - if you have different info, please let me know!

Sure - real world performance will not be even close to the theoretical maximum but there may still be some room for improvement

It all depends on how one looks at it, I read this differently:

http://infocenter.arm.com/help/topic/co ... dgcfe.html

rather, it has a register file of 64-bit registers which it can map to 128-bit registers as well. But only as a matter of convenience, it will sometimes take double the cycles to perform an instruction on a q-word. It depends on the instruction:

http://infocenter.arm.com/help/index.js ... 06s06.html

Eg. for fp32 addition, vadd takes one cycle only for a d-word not a q-word. So a 128-bit vadd will take two cycles. Some others take 1 cycle even for a q-word, eg. integer addition.
There is, but I think the limit is 1.6GFLOPS not 3.2 :)

Ah OK I see - you're right.

Well, at least most ALU instructions seem to be single cycle and 1.6 GFLOPS is also not too bad for a low power CPU :)

Here is a quote from a guy inside ARM -I asked him yesterday as I wanted to be sure myself :)
I hope this clarifies things a bit.

Indeed, it does.
Thanks for that info!

So it looks like dual-core A9 will be able to get to G4 performance level in about a fraction of its power consumption. Great!