The Lynnfield Preview: Rumblings of Revenge
by Anand Lal Shimpi on May 29, 2009 1:00 PM EST- Posted in
- CPUs
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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ssj4Gogeta - Friday, May 29, 2009 - link
There's always the dual-core Nehalem Clarkdale for the mainstream market. And I think they'll launch lower clock Lynnfields too, like Anand said.I think Intel did a good job by separating its high-end processors from the mainstream ones and launching them as a different series. So now instead of having one $1200 extreme part, we have 3 high-end parts, with the lowest priced one a very affordable option for geeks who are on a budget.
ssj4Gogeta - Friday, May 29, 2009 - link
Congratulations Intel, you've created a beast.What is AMD going to do now? I don't think they have any new cores ready for launch this year. If Lynnfield offers the same performance as i7 920 for Phenom II prices, AMD will either have to bump up their clock speeds ridiculously, or lower their prices yet again. Things aren't looking good for AMD. Lynnfield turns out to be better than I expected.
And I HATE Intel and their tick-tock. Actually I can't decided whether to hate or like it. It's good that they're advancing our planet's technology at a really fast pace so we'll be prepared when aliens attack. But which damn processor do I buy??? They launch a new series every year, and a new stepping every few months. Which one to buy? WHEN to buy??? My parents won't buy me processors every 6 months!
MadMan007 - Friday, May 29, 2009 - link
You could always do what people did back in the day - upgrade when your current hardware no longer does what you need it to do. I know, crazy right!?Griswold - Friday, May 29, 2009 - link
Its only a crazy concept if daddy is paying for those upgrades all the time - you and the rest of us know its the right thing to do. :]Jaramin - Friday, May 29, 2009 - link
Looking at AMD's roadmap, I fear this is going to hurt a lot :( If the pricing is good, it could confine AMD into the lower mainstream segment.Hyperion1400 - Friday, May 29, 2009 - link
That remains to be seen. Don't Istanbul heading for market at around the same time as Core-i5. There has been little information leaked about Istanbul and no performance numbers have come to light. So, as of now, it is impossible to predict how competitive AMD's offerings will be. Not to mention we have Magny Cours to look forward too in 1H 2010.ssj4Gogeta - Friday, May 29, 2009 - link
But Istanbul is just a 6-core Opteron. In other words, a server chip.Hyperion1400 - Saturday, May 30, 2009 - link
As was Barcelona and Shanghai. But, that didn't seem to stop them from releasing them on the main stream market.Spoelie - Saturday, May 30, 2009 - link
but costs would be too prohibitivePhII is already similar in die size as bloomfield, and is forced to be priced lower for competitive reasons.
You think AMD won't be hurting if it sells an even larger die to compete with a smaller-than-bloomfield die, in a market where having more than 6 cores is questionable value at best?
No, only thing amd can do is crank up clock speeds, try to get 3.4 and 3.6ghz models out the door
Spoelie - Saturday, May 30, 2009 - link
Oh and up the uncore clock on them as well, preferably 2.4ghz, but might make them look worse in power consumption comparisons