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Groups > comp.lang.c > #59619 > unrolled thread
| Started by | Weng Tianxiang <wtxwtx@gmail.com> |
|---|---|
| First post | 2015-04-05 06:50 -0700 |
| Last post | 2015-04-07 10:48 -0500 |
| Articles | 3 on this page of 83 — 19 participants |
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Does each core of 8-core Intel processor has an independent floating X87 unit? Weng Tianxiang <wtxwtx@gmail.com> - 2015-04-05 06:50 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Noob <root@127.0.0.1> - 2015-04-05 17:17 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Melzzzzz <mel@zzzzz.com> - 2015-04-05 17:35 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 11:21 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Melzzzzz <mel@zzzzz.com> - 2015-04-05 18:40 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 11:56 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? fir <profesor.fir@gmail.com> - 2015-04-05 10:08 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 13:17 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-07 10:10 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-07 10:26 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-07 23:40 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Bartc <bc@freeuk.com> - 2015-04-07 23:06 +0100
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-08 01:23 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-07 23:15 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-07 20:16 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-08 09:27 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-08 09:44 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Melzzzzz <mel@zzzzz.com> - 2015-04-05 19:37 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 18:50 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-05 22:29 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 23:09 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-06 01:54 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-06 07:44 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-07 10:16 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-07 03:32 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-07 12:48 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Richard Heathfield <rjh@cpax.org.uk> - 2015-04-07 11:57 +0100
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-07 13:33 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-07 15:21 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-04-07 17:15 +0000
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Tim Prince <tprince@computer.org> - 2015-04-07 14:21 -0400
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Keith Thompson <kst-u@mib.org> - 2015-04-05 13:08 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 15:27 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Noob <root@127.0.0.1> - 2015-04-05 19:04 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Melzzzzz <mel@zzzzz.com> - 2015-04-05 19:38 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? fir <profesor.fir@gmail.com> - 2015-04-05 10:46 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Keith Thompson <kst-u@mib.org> - 2015-04-05 13:12 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? fir <profesor.fir@gmail.com> - 2015-04-05 09:51 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 12:18 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? jacobnavia <jacob@jacob.remcomp.fr> - 2015-04-06 01:30 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 19:27 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? christian.bau@cbau.wanadoo.co.uk - 2015-04-07 23:58 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-08 08:08 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Melzzzzz <mel@zzzzz.com> - 2015-04-06 03:36 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-07 10:27 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-07 10:39 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? christian.bau@cbau.wanadoo.co.uk - 2015-04-07 23:47 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 11:04 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Melzzzzz <mel@zzzzz.com> - 2015-04-05 18:20 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-05 11:43 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-04-05 20:28 +0000
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-04-05 14:46 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? fir <profesor.fir@gmail.com> - 2015-04-05 15:01 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Keith Thompson <kst-u@mib.org> - 2015-04-05 13:17 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Paul <nospam@needed.com> - 2015-04-05 14:31 -0400
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-07 11:01 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-05 22:34 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Weng Tianxiang <wtxwtx@gmail.com> - 2015-04-05 23:39 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-06 02:06 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-06 08:57 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-06 12:38 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-06 16:30 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Stephen Sprunk <stephen@sprunk.org> - 2015-04-06 17:10 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Ian Collins <ian-news@hotmail.com> - 2015-04-07 10:16 +1200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Melzzzzz <mel@zzzzz.com> - 2015-04-07 02:23 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-06 17:36 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-06 17:41 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-06 20:09 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Richard Damon <Richard@Damon-Family.org> - 2015-04-06 22:44 -0400
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? David Brown <david.brown@hesbynett.no> - 2015-04-07 11:11 +0200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Weng Tianxiang <wtxwtx@gmail.com> - 2015-04-06 08:04 -0700
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-06 12:43 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Paul <nospam@needed.com> - 2015-04-06 14:52 -0400
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? BGB <cr88192@hotmail.com> - 2015-04-06 17:09 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Paul <nospam@needed.com> - 2015-04-06 11:11 -0400
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-06 12:47 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Stephen Sprunk <stephen@sprunk.org> - 2015-04-06 17:15 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Robert Wessel <robertwessel2@yahoo.com> - 2015-04-07 03:41 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Ian Collins <ian-news@hotmail.com> - 2015-04-07 21:19 +1200
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Stephen Sprunk <stephen@sprunk.org> - 2015-04-07 10:37 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Tim Prince <tprince@computer.org> - 2015-04-07 12:13 -0400
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Stephen Sprunk <stephen@sprunk.org> - 2015-04-09 12:34 -0500
Re: Does each core of 8-core Intel processor has an independent floating X87 unit? Stephen Sprunk <stephen@sprunk.org> - 2015-04-07 10:48 -0500
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| From | Tim Prince <tprince@computer.org> |
|---|---|
| Date | 2015-04-07 12:13 -0400 |
| Subject | Re: Does each core of 8-core Intel processor has an independent floating X87 unit? |
| Message-ID | <coie0uFnrh4U1@mid.individual.net> |
| In reply to | #59764 |
On 4/7/2015 11:37 AM, Stephen Sprunk wrote: > > I'd love to see an x86 chip with such a design for similar workloads, > but Intel doesn't seem interested in taking SMT past 2 threads per core, > and AMD doesn't seem interested in SMT at all. > That's a bit over-stated. Current Intel(r) Xeon(tm) Phi supports 4 thread contexts in hardware for each core, and 2 or 3 concurrent threads per core are needed to drive the VPU to full performance. Recent AMD CPUs supported vectorized double precision by coupling pairs of cores, which seems a lot like some variation on SMT when the pair of cores can support 2 threads in single precision but not double.
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| From | Stephen Sprunk <stephen@sprunk.org> |
|---|---|
| Date | 2015-04-09 12:34 -0500 |
| Subject | Re: Does each core of 8-core Intel processor has an independent floating X87 unit? |
| Message-ID | <mg6d8f$9np$1@dont-email.me> |
| In reply to | #59768 |
On 07-Apr-15 11:13, Tim Prince wrote: > On 4/7/2015 11:37 AM, Stephen Sprunk wrote: >> I'd love to see an x86 chip with such a design for similar workloads, >> but Intel doesn't seem interested in taking SMT past 2 threads per core, >> and AMD doesn't seem interested in SMT at all. > > That's a bit over-stated. Current Intel(r) Xeon(tm) Phi supports 4 > thread contexts in hardware for each core, and 2 or 3 concurrent > threads per core are needed to drive the VPU to full performance. That's an FP accelerator for the HPC market, not a general-purpose CPU. > Recent AMD CPUs supported vectorized double precision by coupling pairs > of cores, which seems a lot like some variation on SMT when the pair of > cores can support 2 threads in single precision but not double. AFAICT, the integer cores are still completely separate with one thread each; all they share is the FPU/VPU. Seems reasonable given that, for the mass market, FPU/VPU intensive code is fairly rare. You'd want a very different design for the HPC or GPU markets, though. S -- Stephen Sprunk "God does not play dice." --Albert Einstein CCIE #3723 "God is an inveterate gambler, and He throws the K5SSS dice at every possible opportunity." --Stephen Hawking
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| From | Stephen Sprunk <stephen@sprunk.org> |
|---|---|
| Date | 2015-04-07 10:48 -0500 |
| Message-ID | <mg0u80$df2$1@dont-email.me> |
| In reply to | #59735 |
On 07-Apr-15 03:41, Robert Wessel wrote: > Stephen Sprunk <stephen@sprunk.org> wrote: >> Niagara was designed for a specific market (database and web >> servers) where FP performance is mostly irrelevant; the FPU >> probably spends most of its time powered off completely, only >> waking up when someone runs server performance reports and such. >> They probably could have left it out completely and relied on >> software emulation instead. > > OTOH, it was a small bit of the chip (1/3 to 1/2 the size of a > single core) and would have been far faster than emulation on a > single core. Quite possibly total throughput on all eight cores for > emulation could have been almost as fast, but on the (valid) > assumption that FP is relatively rare in server code, it still makes > sense to provide decent performance when it does show up - Niagara's > cores were pretty darn slow to begin with, hitting even a modest > patch of FP would have been really slow if it would have had to drop > to emulation. And so long as you don't get too many cores hitting > patches of FP at once, it works fairly well. I'm sure they did the simulations to validate their decision, and for a cost that low, even intuitively it seems like a decent trade-off. > And a lot of web server workloads, while not FP intensive, still > execute a reasonable amount of FP - most of the scripting languages > that would run there pretty much make doubles the default numeric > type. They're going to spend a lot of time in filesystem/disk code, network code, database code, web server code, JVM code, etc., and those are all written in C and mostly/exclusively use integers. A little bit of emulated FP shouldn't hurt much, but maybe it's still enough to justify 1/8th of an FPU per core. Maybe those transistors could have been spent on more cache, but given that the justification for that entire class of design is that such workloads thrash the cache, no matter the size, probably not. S -- Stephen Sprunk "God does not play dice." --Albert Einstein CCIE #3723 "God is an inveterate gambler, and He throws the K5SSS dice at every possible opportunity." --Stephen Hawking
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