The difference between VFPv4 and VFPv3, between SIMD2 and SIMD?

Dear,

I am developing projcet using cortex-A8, I optimize some algorithm code on cortex-A8 cpu.

The code shall be ported to cortex-A15 in near future, I got some information about BEON and VFP from website,the different NEON / VFP version betweem cortex-A8 and cortex-a15.

cortex-a8: SIMD/VFPv3

cortex-a15:SIMD2/VFPv4

could you tell me the detailed difference of noen version between cortex-A8 and cortex-a15?

Thank you in advance.

BRS,

Meng