16 registers

[Magnum]

If you have a 64 bit system, does that mean you in effect have 16  32 bit registers ?

[Magnum]

Whoops, guess that should be 8 registers.

[clive]

AMD64 has 16 64-bit general purpose registers. Where AX was 16-bit, EAX is 32-bit, RAX is 64-bit.
It also provides 16  XMM 128-bit SIMD registers.
http://en.wikipedia.org/wiki/X86-64

If you're talking non-x86 64-bit systems there are a bunch of alternative 64-bit register schemes.