On 08/24/11 12:05 AM, Kenneth Porter wrote:
> As someone who coded in assembler for PDP-11, PDP-10, 8086, and 68000, I
> have to report that more registers is a Very Good Thing. Just how many more
> registers do you get when going to 64-bit?
indeed, thats the main performance gain, other than the increased
address space. in fact, for RISC architectures such as SPARC, Power,
MIPS, where there were already sufficient registers, and for which the
64 bit extensions were virtually identical to the existing 32 bit base
architecture, going to 64 bit code for most applications that dont need
additional linear address space is actually a performance /penalty/ due
to the increase in size of the code base for the longer offsets and
addresses.
On the x86_64, there are 16 64bit registers instead of the 8 16/32 bit
of the 8086/386 instruction set architecture (of those 8 or 16, two are
the dedicated stack pointer and base pointer registers, leaving really
only 6 or 14 general purpose registers).
--
john r pierce N 37, W 122
santa cruz ca mid-left coast
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