Intel's Pentium Extreme Edition 955: 65nm, 4 threads and 376M transistors
by Anand Lal Shimpi on December 30, 2005 11:36 AM EST- Posted in
- CPUs
Literally Dual Core
One of the major changes with Presler is that unlike Smithfield, the two cores are not a part of the same piece of silicon. Instead, you actually have a single chip with two separate die on it. By splitting the die in two, Intel can reduce total failure rates and even be far more flexible with their manufacturing (since one Presler chip is nothing more than two Cedar Mill cores on a single package).
In order to find out if there was an appreciable increase in core-to-core communication latency, we used a tool called Cache2Cache, which Johan first used in his series on multi-core processors. Johan's description of the utility follows:
Not only did we not find an increase in latency between the two cores on Presler, communication actually occurs faster than on Smithfield. We made sure that it had nothing to do with the faster FSB by clocking the chip at 2.8GHz with an 800MHz FSB and repeated the tests only to find consistent results.
We're not sure why, but core-to-core communication is faster on Presler than on Smithfield. That being said, a difference of less than 9ns just isn't going to be noticeable in the real world - given that we've already seen that the Athlon 64 X2's 100ns latency doesn't really help it scale better when going from one to two cores.
One of the major changes with Presler is that unlike Smithfield, the two cores are not a part of the same piece of silicon. Instead, you actually have a single chip with two separate die on it. By splitting the die in two, Intel can reduce total failure rates and even be far more flexible with their manufacturing (since one Presler chip is nothing more than two Cedar Mill cores on a single package).
The chip at the bottom of the image is Presler; note the two individual cores.
In order to find out if there was an appreciable increase in core-to-core communication latency, we used a tool called Cache2Cache, which Johan first used in his series on multi-core processors. Johan's description of the utility follows:
"Michael S. started this extremely interesting thread at the Ace's hardware Technical forum. The result was a little program coded by Michael S. himself, which could measure the latency of cache-to-cache data transfer between two cores or CPUs. In his own words: "it is a tool for comparison of the relative merits of different dual-cores."Armed with Cache2Cache, we looked at the added latency seen by Presler over Smithfield:
"Cache2Cache measures the propagation time from a store by one processor to a load by the other processor. The results that we publish are approximately twice the propagation time. For those interested, the source code is available here."
| Cache2Cache Latency in ns (Lower is Better) | |
| AMD Athlon 64 X2 4800+ | 101 |
| Intel Smithfield 2.8GHz | 253.1 |
| Intel Presler 2.8GHz | 244.2 |
Not only did we not find an increase in latency between the two cores on Presler, communication actually occurs faster than on Smithfield. We made sure that it had nothing to do with the faster FSB by clocking the chip at 2.8GHz with an 800MHz FSB and repeated the tests only to find consistent results.
We're not sure why, but core-to-core communication is faster on Presler than on Smithfield. That being said, a difference of less than 9ns just isn't going to be noticeable in the real world - given that we've already seen that the Athlon 64 X2's 100ns latency doesn't really help it scale better when going from one to two cores.
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Betwon - Friday, December 30, 2005 - link
NO.The speed is still very slow for AMD--latency 101ns. Even it is slow than the latency of RAM(5x ns -- 8x ns)
With so large a latency, we don't find any benefits for those apps which communicate frequently between 2 cores. But it will hurt the performance.
The best way for core-communication -- share L2 cache. The latency of yonah will be very low, much faster than AthlonX2 and Presler.
mlittl3 - Friday, December 30, 2005 - link
Not to mention the crossbar switch would not be possible if the dies were separated. Remember AMD did dual-core the right way by bringing the memory controller on die and using the crossbar switch to switch memory communications between the two cores with little latency. If the dies were separated the crossbar switch would have to be moved off die and that would make the whole point of on-die memory controller, well, pointless really.ricardo dawkins - Friday, December 30, 2005 - link
S939 AMD chip when these chips are phasing out by M2 and the like or i'm crazy ?Calin - Tuesday, January 3, 2006 - link
Because you can still find good processors for socket 754. Socket 939 will become the "value" or "mid-range" socket for AMD, and not the premier one (like it is now). New chips will come to socket 939, but the top of the line will be the new M2 - so a new 939 now is a good investment, that should be upgradable in a couple of yearsGriswold - Friday, December 30, 2005 - link
Would you rather recommend presler when the next big thing will yet again bring a new socket?ricardo dawkins - Friday, December 30, 2005 - link
Are you dead sure Conroe will need a new socket ?...LGA775 is with us for a few more years..stop spreading FUD. BTW, I'm not a intel fanboy but I read a lot of news.coldpower27 - Friday, December 30, 2005 - link
No your correct, there are images of the Conroe processor showing that it pin out is LGA775. I predict most likely we will ditch LGA775 when Intel ditiches NetBurst FSB technology in favor of CSI in 2008.JarredWalton - Friday, December 30, 2005 - link
Conroe should be socket 775, but it appears that it will require a new chipset - possibly 965/Broadwater, but it might also be something else. I am almost positive that 945/955 *won't* support the next gen Intel chips, which is too bad.michaelpatrick33 - Friday, December 30, 2005 - link
The power draw numbers from other websites are nothing short of frightening for Intel. They have closed the gap with AMD's current X2 4800 but at double the power draw. It is getting ridiculous that a 65nm processor uses more power at idle than a competitor's 90nm draw at full load. Conroe is the true competitor to AMD in 2006 and it will be interesting to see the power numbers for the FX-60 and new AMD socket early next year.Spacecomber - Friday, December 30, 2005 - link
I thought that part of the big news coming out in prior reviews of this chip was its overclocking potential. Not that anyone would necessarily buy this processor in order to overclock it, but it was suggestive of what the core was capable of.Unless I overlooked it, overclocking wasn't mentioned in this article.
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