-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Chuck,
On 3/1/2011 6:09 PM, Caldarale, Charles R wrote: >> From: Christopher Schultz [mailto:ch...@christopherschultz.net] >> Subject: Re: [OT] IIS7/isapi/tomcat performance > >> I don't understand why communicating a 64-bit value over a >> 64-bit bus would take longer than communicating a 32-bit >> value over a 64-bit bus: > > Because you get *two* 32-bit values for one transfer, not just one. If, as you say, Intel can move 64 /bytes/ across a data path (if you prefer that phrase over "the bus") then the word size really does make a difference, here. They should be getting 16 32-bit words across such a data path or 8 64-bit words. If the pointers are doubling in size, this makes 64-bit mode go slower because you get half the throughput when using word-sized values. Since pointers in general are word-sized, they always suffer while other (usually smaller) data does not. The key is that the data path(s) are actually much wider than the word size, which I didn't realize. >> I also get that some processors (like Itanium) have an x84 >> processor core on the die > > (Presumably, you meant x86.) Sorry, Itanium was notoriously bad at running > 32-bit apps. I did mean x86. Lots of typing yesterday. The new Itaniums are supposed to be actually worth it, though. >> getting the data from point A to point B shouldn't matter > > Sure it does, if you can batch multiple operand accesses together (which > current Intel cores do). > >> I suppose of the CPU knew it was in a 32-bit mode, it could >> adjust the number of clock ticks it had to wait around for >> 32-bit data to go through an adder, but that seems overly >> complicated for a straightforward CPU task. > > Simple adders have only used one cycle for decades, regardless of the width. If the clock tick is long enough :) - -chris -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk1u/FUACgkQ9CaO5/Lv0PBBHACfQsXMTwCmZywZrihKJI3M0k5c BdoAn3VrrewxdTHZU0TZvR1pbQcKFwVj =1Png -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
