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Programs 64b processor
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Robert Hyatt



Joined: 27 Feb 2006
Posts: 15816
Location: Birmingham, AL
PostPost subject: Re: Programs 64b processor    Posted: Mon Jun 11, 2012 4:48 pm Reply to topic Reply with quote
syzygy wrote:
neelbasant wrote:
putting data in 32-bit processing is slower than 64-bit processing.

Only if you really need to process 64-bit values such as bitboards. Many many applications do not need 64-bit values, and in general they won't run faster as a result of compiling as a 64-bit program. In general, they run slower because 64-bit instructions and pointer values take up more space and therefore consume more memory bandwidth and cache.

The exception is the x86-32/64 architecture. On this architecture, 64-bit programs generally are faster than the equivalent 32-bit programs. The reason is that the x86-64 architecture provides double the amount of cpu registers compared to the x86-32 architecture. This has basically nothing to do with the fact that it is a 64-bit architecture. What happened is that AMD (who designed the x86-64 instruction set which was later adopted by Intel) took the transition to 64-bit as an opportunity to improve on the 32-bit x86 architecture by extending the set of general purpose registers (plus some other improvements).

Quote:
You can imagine it as .
You have 32 lane(bit) for transportation.\
& now you have 64 lane ( bit) for transportation.

Only helps where 32-bit values are not enough.


There ARE advantages to 64 bits beyond just 64 bits. For example, 8 additional general-purpose registers, something the x86 really needs. And this is a bit more than "doubling" given that we only have eax-edx in 32 bit mode, and get 8 more in 64 bits, so really tripling. And when you consider how eax/edx are used in multiply, the number of extra registers becomes even more significant. I have not seen many applications that run slower in 64 bit mode, not that they don't exist. But they are a small minority. Most run faster. And those that are left are mostly just more modest gains, or break-even. And some, notably bitboard chess engines, run significantly faster. Overall it is a significant gain no matter what the software...
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Subject Author Date/Time
Programs 64b processor Krzych Cybulsky Sat Jun 09, 2012 8:19 am
      Re: Programs 64b processor Vincent Lejeune Sat Jun 09, 2012 9:38 am
      Re: Programs 64b processor Lucas Braesch Sat Jun 09, 2012 10:27 am
            Re: Programs 64b processor Ronald de Man Sat Jun 09, 2012 12:37 pm
            Re: Programs 64b processor Ralph Stoesser Sat Jun 09, 2012 8:45 pm
                  Re: Programs 64b processor Lucas Braesch Sun Jun 10, 2012 4:56 am
      Re: Programs 64b processor Neel Basant Sat Jun 09, 2012 4:09 pm
            Re: Programs 64b processor Ronald de Man Sat Jun 09, 2012 4:33 pm
                  Re: Programs 64b processor Robert Hyatt Mon Jun 11, 2012 4:48 pm
                        Re: Programs 64b processor Ronald de Man Mon Jun 11, 2012 6:23 pm
      Re: Programs 64b processor Krzych Cybulsky Sat Jun 09, 2012 5:50 pm
            Re: Programs 64b processor Ronald de Man Sat Jun 09, 2012 6:15 pm
                  Re: Programs 64b processor Greg Simpson Sun Jun 10, 2012 5:08 am
            Re: Programs 64b processor Lucas Braesch Sun Jun 10, 2012 1:23 am
                  Re: Programs 64b processor Ernest Bonnem Sun Jun 10, 2012 9:04 pm
                  Re: Programs 64b processor Krzych Cybulsky Mon Jul 02, 2012 6:49 pm
                        Re: Programs 64b processor Lucas Braesch Tue Jul 03, 2012 12:25 pm
                              Re: Programs 64b processor Ernest Bonnem Tue Jul 03, 2012 8:43 pm
      Re: Programs 64b processor George Speight Sat Jun 09, 2012 11:08 pm
            Re: Programs 64b processor Lucas Braesch Sun Jun 10, 2012 1:51 am
                  Re: Programs 64b processor George Speight Tue Jul 03, 2012 10:15 am
                        Re: Programs 64b processor Lucas Braesch Tue Jul 03, 2012 12:26 pm
                              Re: Programs 64b processor George Speight Thu Jul 05, 2012 7:19 am
            Re: Programs 64b processor Krzych Cybulsky Mon Jun 11, 2012 4:48 pm
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