The Lynnfield Preview: Rumblings of Revengeby Anand Lal Shimpi on May 29, 2009 1:00 PM EST
- Posted in
Lynnfield’s Secret? Turbo Mode
The current Core i7 runs at a multiple of its BCLK, which is 133MHz. The Core i7-920 runs at 20x BCLK (2.66GHz) while the i7-965 runs at 24x BCLK (3.2GHz). If the chip isn’t running anywhere near its max TDP, the i7 will overclock itself by one speed bin (133MHz). Now say you’re running a single-threaded application that’s got only one core active, if the chip is cool enough the i7 will overclock itself by two speed bins (266MHz).
Turbo mode on the i7 works well and as I found is generally responsible for a 3 - 4% increase in performance. Despite its benefits, the i7’s Turbo mode is very conservative. Our own overclocking tests show that i7s have no problems running at up to 3.8GHz without any additional cooling or voltage, even with all four cores under full load. Given that it was Intel’s first Nehalem architecture, I can understand the hesitation not to go crazy with turbo.
The second version of Intel’s Nehalem turbo mode came with the high end Nehalem Xeon processors. While the single-socket processors worked just like the desktop i7s, the higher end dual-socket Xeons can turbo up more aggressively.
The Xeon E5520, E5530 and E5540 can all boost their clocks by one bin if 3 or 4 cores are active, but two bins if 1 or 2 are active. The X5000 series gets even more aggressive; with 3 or 4 cores active the chips can overclock themselves by up to 266MHz, and if 1 or 2 cores are active they can turbo up an additional 400MHz.
Lynnfield marks Intel’s third generation Nehalem turbo and is correspondingly more awesome.
The leaked roadmaps show that the two higher end Lynnfields can turbo up to five bins, or 667MHz while the entry level Lynnfield can turbo up to four bins (533MHz). I’m guessing this is for a single active core, but what about when more than one core is active? The table below has the turbo specs for the Xeon X5570 (95W TDP), the Core i7-940 (130W TDP) and my guesstimates for the 2.93GHz Lynnfield (95W TDP):
|Processor||Clock Speed||Max Turbo|
|4 Cores Active||3 Cores Active||2 Cores Active||1 Core Active|
|Intel Xeon X5570||2.93GHz||3.2GHz||3.2GHz||3.33GHz||3.33GHz|
|Intel Core i7-940||2.93GHz||3.06GHz||3.06GHz||3.06GHz||3.2GHz|
|Intel Lynnfield ESTIMATE||2.93GHz||3.2GHz||3.2GHz||3.60GHz||3.60GHz|
Given the similarity in clock speed and TDP to Intel's Xeon X5570, I'm guessing the 2.93GHz Lynnfield will follow the same 2/2/3/3 turbo pattern as the Xeon. The higher max turbo frequency means that we'll at least see 3.60GHz with only 1 core active and I'm not really sure what will happen if two cores are active; if Intel follows the Xeon pattern then we'll see 3.6GHz as well, but we may very well see 3.33GHz or 3.46GHz instead when only two cores are active.
Either way a quad-core Lynnfield, thanks to its aggressive turbo mode, will end up delivering good performance regardless of the number of concurrent threads. Forget about it being a quad-core CPU and just think of it as a CPU that will perform as best as possible given its 95W thermal envelope. This, my friends, is the future of multi-core processors. It doesn't matter how many cores you have, just view them as execution resources; if you only need two powerful cores, that's what you get, and if you need to run 8 threads then that's what you'll get. Imagine what we'll get on the 4th or 5th generation of turbo modes.
To those who are wondering why Lynnfield even makes sense, I believe its turbo mode will be its saving grace. I'm more puzzled by the i7-920 at this point.
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Hyperion1400 - Friday, May 29, 2009 - link*Presses imaginary edit button*
"Don't forget, Istanbul is heading..."
MadMan007 - Friday, May 29, 2009 - linkAwesome preview, too bad about HT.
I think there's an error with the labelling for the first pass x264 encoding test on pg 7.
dwade123 - Friday, May 29, 2009 - linki5 is perfect for ITX motherboard compared to i7. Can't wait!!!
nubie - Friday, May 29, 2009 - link+1 they need to get an ITX motherboard for these immediately, if not sooner!
One chip motherboard with integrated PCI-e x16 is perfect for ITX gaming system, should drive the cost of them way way down :)
Dual x8 PCI-e 2.0 is fine for Crossfire or SLi (not that I would ever plan to run them)
Is there any chance of an nVidia 9800/GTS250 integrated ITX motherboard? I would just about die if you could get one of those for around $200 ;)
Mr Perfect - Friday, May 29, 2009 - linkAbsolutely! Can you imagine all that horsepower in such a small FF? Hopefully Zotac makes another mini-ITX with a x16 slot on it.
Depeche - Friday, May 29, 2009 - linkBy the time I got the i7 the i5 comes out and when I finally get the i5 some other series comes out. I can't keep up :)
Get these CPUs in the Bench Beta :P
A5 - Friday, May 29, 2009 - linkThis kind of thing (and the motherboard round-ups that used to be here) were the reasons I came to AT. If this pans out, I'm definitely building a Lynnfield system to replace my aging Socket-939 rig.
philosofool - Monday, August 3, 2009 - linkAs a bonus, if you buy into LGA 1156 now, you will probably be able to get a considerable upgrade in 2 years just by replacing the CPU. The LGA 1156 socket should last awhile, at least as long as LGA 775, but maybe longer, because the memory controller was the big reason for a new socket.
nuudles - Monday, June 1, 2009 - linkI agree, great article!
I also have only an an old s939 rig (opteron 150 - so i am still in the single-core world), and I also suspect this is the one I have been waiting for:)
I initially thought I would wait a bit longer till the 32nm parts come out (damn Intel for their tick-tock), but since the first 32nm parts will be more mainstream (2C/4T) where the Lynnfields are high-end mainstream (or whatever its called) I think the 2.8 Lynnfield would suit me nicely for the next 3-4 years.
faxon - Monday, June 1, 2009 - linkyea i would wait man. i upgraded from my 939 rig to an e5200 and now i have a Q9650 @ 4GHz @ 1.296vcore. given the performance benchmarks, even a 3.7ghz lynnfield will probably outperform my 4GHZ quad in games