[mythtv-users] 32 vs. 64 bit, any significant difference?

belcampo belcampo at zonnet.nl
Thu Dec 17 19:31:59 UTC 2009

Johnny wrote:
>> People often forget that the x86-64 provides twice as many general purpose
>> registers as 32-bit x86.  They have twice as many SSE registers as well.
>> Depending on workload, performance can be either worse (due to larger
>> pointers) or better (due primarily to the increase in registers).
>> If I recall, transcoding is one of the poster children for running 64-bit.
>> I don't have numbers on hand but I definitely noticed an improvement.  I
>> think 15% improvement is the general rule of thumb although I've heard of
>> 30% improvements when transcoding as well.  As with all such things, your
>> mileage will probably vary :)
> Another benefit is that the compiler can make much more efficient
> optimizations because x86-64 includes all the modern changes to the
> x86 ISA (SSE etc) that modern chips support. When you use 32-bit it is
> compiled against the ISA that an Intel 386 used or maybe a 686 (e.g.
> Pentium II, Pentium III). But I think in everyday use you aren't
> likely to feel much difference from this (approximately 5%
> improvement). But in processes that are very computationally intense
> and benefit from newer ISA changes like SSE, then you will see larger
> improvements on the order of 10%-20%. Much of the MMX and SSE
> extensions added op-codes for vector operations, etc, that are
> targeting at multimedia stuff like transcoding. So that is one of the
> areas that sees the most benefit.
Are there any hard facts that prove these assumptions ?
Transcoding 32 vs 64bit 512MB vs 2-8GB
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