The Lynnfield Preview: Rumblings of Revengeby Anand Lal Shimpi on May 29, 2009 1:00 PM EST
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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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Jabbernyx - Monday, June 1, 2009 - linkYou're forgetting the $10 off promo code and 5% Live cashback ;)
Randomblame - Friday, May 29, 2009 - linkAnyone else irritated that when this launches intel will have 5 sockets going?
Shall we count em?
lga 775 core 2
lga 1366 i7
lga 1160 lynfield
lga 771 xeon penryn
lga 611 itanium
Did I miss any?
Anonymous Freak - Sunday, May 31, 2009 - linkIf you're going to include Itanium; you might as well include the mobile sockets as well.
Last October, Intel had one desktop, three server, and two mobile sockets:
LGA775 on the desktop was it.
LGA771 for dual Xeon, PGA-604 for quad-plus Xeon. (And LGA775 for single-socket servers, where the processors were just Core 2 series processors slapped with a "Xeon" name on them, so I'm keeping that with 'desktop'.) PAC-611 is Itanium.
Socket M is the slightly older mobile socket, Socket P is the newer. One could say that Socket M was already dead in October.
Early next year, we will have three desktop, two server, and two mobile sockets.
LGA 775 will be the low-end Core 2 socket, LGA 1366 for i7, and LGA 1156 for Lynnfield. Lynnfield should overtake Core 2 very quickly, especially after the integrated-graphics chips come out, and drop to two desktop sockets, though.
LGA 1366 doubles as the single and dual server socket; and the new "Nehalem EX" will in all likelihood have a new socket shared with the new Itanium (from reasonable guesses, anyway.)
Mobile will have just Socket P until the mobile Nehalems launch, when a new mobile Nehalem socket will be out.
Sorry, but LGA 771 is already dead. Its processors are completely obsolete at this point, by Nehalem-EP. And PGA-604 (which you missed,) as well as PAC-611, will be obsoleted by the Nehalem-EX socket. (Again, just guessing. The entire point of QPI was to make Xeon and Itanium share resources, so I would imagine they would use the same socket. Especially with Xeons now at higher power draw than even the highest draw Itanium; there is no reason for Itanium's goofy socket-with-power-pod arrangement any more.
Drazick - Friday, May 29, 2009 - linkThough the system looks good.
I really liked the one chip Idea (Chipset).
I hope Intel eventually let nVidia develop chipsets for this platform.
Why don't you think the regular PCIE X16 lane in this system is enough for GPGPU? It might not be the best but for Encoding some movies and Accelerating Matlab it should be enough, no?
Anand Lal Shimpi - Saturday, May 30, 2009 - linkI didn't mean to imply that 16 PCIe 2.0 lanes aren't enough for GPGPU. But if you're doing a *lot* of compute over the PCIe bus, perhaps over multiple very high end GPUs, then you'll probably want QPI. This is more of a HPC or head-in-the-clouds-desktop scenario though.
It should be more than enough for GPU based video encode or math.
ssj4Gogeta - Friday, May 29, 2009 - linkEven if Intel allows Nvidia, they can't make integrated graphics for i5 because the chip is connected to the chipset via 2 GB/s DMI, which will bottleneck it.
Doormat - Friday, May 29, 2009 - linkUntil the price of 4GB DDR3 sticks come down (and I could put 16GB of RAM on the board), I think the i7 is where its at. At least with i7, I can go with 12GB now and then upgrade to 24GB later (12GB I need, 24GB I don't know...).
A5 - Friday, May 29, 2009 - linkIf you NEED 12GB, then Lynnfield isn't going to be for you. Intel would much rather you use Xeons for that kind of workload anyway :P
ltcommanderdata - Friday, May 29, 2009 - linkSo with mainstream Nehalems not having any QPI links and high-end Nehalems with QPI not needing them, are third-party IGPs dead? It seems that even if nVidia can win their legal issues with Intel, the technical challenges of being limited to DMI seem to make the Intel chipset business unprofitable. Higher priced chipsets with IGPs would be bandwidth limited over DMI and just making southbridges doesn't seem very glamourous or profitable.
Anand Lal Shimpi - Saturday, May 30, 2009 - linkNVIDIA claims to have DMI based IGPs in development for LGA-1156 platforms. We'll see how good they are and if they do end up coming to market despite the legal issues.
In the long run I don't expect the 3rd party chipset business to survive on either platform (AMD or Intel). Unless either company is horribly deficient at some basic platform need I'd expect desktop and mobile AMD CPUs to use AMD chipsets and for desktop and mobile Intel CPUs to use Intel chipsets. It may take a couple of years to get there but I think the end result is inevitable.
I believe that's why we're seeing such a strong push from NVIDIA lately with things like Ion. Attempting to stay put when we know what the tide is about to do is a difficult task.