Last week Intel introduced its highly anticipated Lynnfield processors under the Core i5 and Core i7 brands. Three chips emerged:
| Processor | Clock Speed | Cores / Threads | Maximum Single Core Turbo Frequency | TDP | Price |
| Intel Core i7-975 Extreme | 3.33GHz | 4 / 8 | 3.60GHz | 130W | $999 |
| Intel Core i7 965 Extreme | 3.20GHz | 4 / 8 | 3.46GHz | 130W | $999 |
| Intel Core i7 940 | 2.93GHz | 4 / 8 | 3.20GHz | 130W | $562 |
| Intel Core i7 920 | 2.66GHz | 4 / 8 | 2.93GHz | 130W | $284 |
| Intel Core i7 870 | 2.93GHz | 4 / 8 | 3.60GHz | 95W | $562 |
| Intel Core i7 860 | 2.80GHz | 4 / 8 | 3.46GHz | 95W | $284 |
| Intel Core i5 750 | 2.66GHz | 4 / 4 | 3.20GHz | 95W | $196 |
We tested exclusively with the Core i7 870 and the Core i5 750, the 860 didn't arrive in my lab until after the review went live. I was spending the greater part of a week with AMD at that time and didn't get to testing until this past weekend. Here's the chip:
What makes the Core i7 860 so interesting is that it's priced on par with everybody's favorite Nehalem: the Core i7 920. The 870 has great turbo modes, but it's nearly twice the price of the 860. The Core i5 750 wins in the price department, but it lacks Hyper Threading - part of what makes Nehalem so tasty in the first place. The 860 effectively gives us the best of both worlds, hence the focus on it for today's review.
I had a few mistakes in my original version of this table, but below you can see the turbo modes offered by the 860. They're not quite as nice as the 870, but the chip is also half as expensive. You'll also see that like the 750 you only get a single bin improvement with 3 or 4 cores active, but like the 870 you get 4 and 5 extra speed bins in the dual and single active core situations:
| Max Speed | Stock | 4 Cores Active | 3 Cores Active | 2 Cores Active | 1 Core Active |
| Intel Core i7 870 | 2.93GHz | 3.20GHz | 3.20GHz | 3.46GHz | 3.60GHz |
| Intel Core i7 860 | 2.80GHz | 2.93GHz | 2.93GHz | 3.33GHz | 3.46GHz |
| Intel Core i5 750 | 2.66GHz | 2.80GHz | 2.80GHz | 3.20GHz | 3.20GHz |
I've explained turbo mode in great detail here. In short, Lynnfield's PCU (Power Control Unit) looks at the number of cores active, shuts down those that are inactive, and uses the thermal savings to boost the clock speed of the active cores - all within the operating specs of the processor. Unless you're overclocking, turbo will never compromise system stability in search of greater performance.
| Single Core | Dual Core | Quad Core | Hex Core | |
| TDP |  |  |  |  |
 |  |  |  |
It works very well in practice, particularly with Windows 7. A question that's come up since the initial review is what happens when background tasks kick in. As I mentioned in the "Speed Limits" section of the Lynnfield review, this is something that can prevent turbo from kicking in:
"There's also the issue of background threads running in the OS. Although your foreground app may only use a single thread, there are usually dozens (if not hundreds) of active threads on your system at any time. Just a few of those being scheduled on sleeping cores will wake them up and limit your max turbo frequency (Windows 7 is allegedly better at not doing this)."
One of the features of Windows 7 is that the OS supposedly does a better job of grouping tasks together on a single core to avoid waking up an adjacent core and negating the gains from turbo mode. I'm still working on finding a good way to measure this but from what I've seen initially, Windows 7 tends to do a good job of grouping threads onto one or two cores - meaning we tend to see the 4-bin or 5-bin turbo modes. The other thing to keep in mind is that the processor can turbo up/down faster than the OS can schedule threads, the benefits of turbo are present even while in the middle of executing a task. Remember what dictates turbo is both thermal dissipation and current consumption; the mix of instructions executed varies depending on the task and even during the task, which in turn varies the frequency your core(s) will run at.
The end result is a system that seems to feel more responsive as well as perform better. Of course none of this matters if you're going to be disabling turbo and just overclocking, but I've addressed that scenario in a separate article today :)
And I don't really have a reason for showing this, but I like tables so here's the current quad-core processor landscape:
| Processor | Manufacturing Process | Die Size | Transistor Count | Socket |
| AMD Athlon II X4 | 45nm | 169 mm2 | 300M | AM2+/AM3 |
| AMD Phenom II X4 | 45nm | 258 mm2 | 758M | AM2+/AM3 |
| Intel Core i7 (Bloomfield) | 45nm | 263 mm2 | 731M | LGA-1366 |
| Intel Core i5/i7 (Lynnfield) | 45nm | 296 mm2 | 774M | LGA-1156 |
| Intel Core 2 Quad Q8xxx | 45nm | 164 mm2 | 456M | LGA-775 |
The Test
| Motherboard: | Intel DX58SO (Intel X58) Intel DP55KG (Intel P55) Intel DX48BT2 (Intel X48) Gigabyte GA-MA790FX-UD5P (AMD 790FX) |
| Chipset: | Intel X48 Intel P55 Intel X58 AMD 790FX |
| Chipset Drivers: | Intel 9.1.1.1015 (Intel) AMD Catalyst 8.12 |
| Hard Disk: | Intel X25-M SSD (80GB) |
| Memory: | Qimonda DDR3-1066 4 x 1GB (7-7-7-20) Corsair DDR3-1333 4 x 1GB (7-7-7-20) Patriot Viper DDR3-1333 2 x 2GB (7-7-7-20) |
| Video Card: | eVGA GeForce GTX 280 |
| Video Drivers: | NVIDIA ForceWare 180.43 (Vista64) NVIDIA ForceWare 178.24 (Vista32) |
| Desktop Resolution: | 1920 x 1200 |
| OS: | Windows Vista Ultimate 32-bit (for SYSMark) Windows Vista Ultimate 64-bit |
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georges1977 - Monday, September 21, 2009 - link
+1khaakon - Sunday, September 20, 2009 - link
Strongly supported. OddTSi makes a good case which I don't think is countered by GourdFM's answer. Users can be educated on this issue, methinks. It will make a better basis for making decisions regarding green computing.GourdFreeMan - Sunday, September 20, 2009 - link
I certainly understand your point of view, but most desktop users will not be concerned with task-oriented energy usage. For nearly all users you will either be in an idle situation (office work/web browsing) or a load situation (gaming)[1] for almost your entire computing session. Normal users don't sit there waiting for a task to complete and then immediately turn off the computer. Even for task oriented computing (e.g. programming, video encoding, rendering) where the user will be waiting for a task to complete before doing more useful work, the reality is that the user will be in one of those two states for the majority of their time over the year. In that sense knowing idle and load power draw is enough for most people.If you were concerned about energy efficiency of distributed computing (e.g. folding@home) your interest with task-oriented energy efficiency would be a valid concern when making purchasing decisions for infrastructure. If you are so concerned about completing the most tasks for the least amount of money on the desktop, your expenses are more likely to be dominated by salaries than energy expenditures or hardware costs. YMMV.
The cost of air conditioning can also complicate the situtation beyond naive energy usage of the computer system. If all you care about is energy usage do you pick a system that will complete the task using 1000 Wh in 4 hours or one that will complete the task using 1005 Wh in 6 hours? If it's a hot summer afternoon and you're in Death Valley you are going to expend a lot more than 5 Wh cooling the room with the former system than the latter. If it's a chilly winter's morning and you're in Siberia the first system will look a lot more attractive.
---
Footnote [1]: Actually gaming isn't so much an ideal load situation anymore since multi-core processors became common. That may change as developers become more adept at exploiting the power of multiple cores.
Eeqmcsq - Saturday, September 19, 2009 - link
> Report it in watt-seconds or kilowatt-hours or however you want, but just report it in units of energy.In other words, you want a measurement in joules for the amount of energy consumed for a task. Techreport.com has such a measurement in their CPU reviews, at least for the Cinebench task.
http://techreport.com/articles.x/17545/13">http://techreport.com/articles.x/17545/13
ProDigit - Saturday, September 19, 2009 - link
Call me crazy, but,85Watts of idle power consumption is crazy!
That's like my Core2Duo Laptop processing @ full power,while transmitting and receiving Wifi @ full speed and range, and HD fully active doing random R/W's; all while the screen's set to maximum brightness.
That's 85 Watts!
While a Corei7 does not seem to do anything at that power consumption.
It, all by itself needs all that power for staying alive! That's just plain crazy!
Anand Lal Shimpi - Saturday, September 19, 2009 - link
Keep in mind there's a much larger power supply and about 1.4 billion transistors of a GeForce GTX 280 idling in that power value as well :)Take care,
Anand
Eeqmcsq - Saturday, September 19, 2009 - link
I asked a similar question in one of the other articles, so pardon me if this sounds repetitive.According to the Turbo charts, the slowest Turbo speed is higher than the stock speed. Why is that? For example, why not just make the 750 a stock GHz of 2.8 GHz instead of 2.66GHz?
has407 - Saturday, September 19, 2009 - link
> According to the Turbo charts, the slowest Turbo speed is higher than the stock speed. Why is that? For example, why not just make the 750 a stock GHz of 2.8 GHz instead of 2.66GHz?To minimize power consumption when the core is active (C0 or C1 states) but under less than full load. (There are also other ways to manage it via, e.g., P-states, S-states, etc. but that's another subject.)
Requisite bad car analogy :) You want the lowest idle RPM that is smooth and responsive; anything more wastes resources and energy.
imsabbel - Sunday, September 20, 2009 - link
Sorry, but it seems nobody is "getting" it.I have a I860 right here.
I checked with CPU-Z.
Even if i run indigorenderer with 8 threads for an hour, it runs with x22.
So either i am the victim of a lucky mixup at intels chip packaging plant and got an 870, or something lese is wrong... (or right. As its runing perfectly fine)
strikeback03 - Monday, September 21, 2009 - link
Crank up the temperature in the case though, and it might drop back to x21.They mentioned previously with the i7 920 that more often than not runs at 2.8GHz