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Why do better intel processors have lower speeds?

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a b à CPUs
July 13, 2011 4:31:46 AM

collegestudent11 said:
I am buying a pc for school, and I was wondering why some of the intel core i7 processors get slower as they increase in price? (GHz)


They do? I dont think that is correct :heink: 
a b à CPUs
July 13, 2011 4:33:14 AM

iirc, i7 processors actually increase in speed if you're looking at the old bloomfields but not the newer sandy bridge afaik.

Sandy bridge has two distinct lines, the K models that have unlocked multipliers and the plain jane ones that cant overclock.

You should clarify if you're buying a laptop or a desktop since i'm thinking you're talking about laptop models and not desktop models.

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July 13, 2011 4:37:20 AM

according to the GHz, some of the better ones are slower, or is there more to it?
a b à CPUs
July 13, 2011 4:40:00 AM

In that case then its quite different.

On laptops the reason they get slower in ghz is due to power requirements. Remember these things can theoretically take up 95w's under full load if their clock speeds were at those of their desktop brethren. This means that when under load, the laptop will run out of juice fairly quickly which means the owner has to plug in more often to recharge.

The battery issue and the fact it does get quite hot under load are some of the major reasons, i think (correct me if im wrong), that they are slower.
July 13, 2011 4:41:20 AM

but if they are slower, how are they better?
a b à CPUs
July 13, 2011 4:43:43 AM

Remember, Core i3s/i5's on the laptop arena are dual cores with or without HT. An i7 is a quad core with 4 HT meaning that when you use programs that can use a lot of resources and computer power, it'll be heads and shoulders above its dual core siblings.

A true quad (i7) will be better than a dual core with ht (i5s). But it will also be more power hungry due to its better performance in heavily threaded and demanding programs.

*some i7s are apparantly dual cores. The quad core ones should have QM in their model names.
July 13, 2011 4:51:08 AM

Although it doesn't apply in this example, remember not all clock cycles are created equal, look at the P4s, they ran at 3.4Ghz but are slower than 1.6Ghz Core 2 even with a single core enabled. There are many other variables that can determine chip speed other than its frequency.
a c 83 à CPUs
July 13, 2011 6:12:01 AM

collegestudent11 said:
according to the GHz, some of the better ones are slower, or is there more to it?


Core count, I've heard some laptop I7's are dual core while others are quad core. I'm not about to go researching Intel's mobile line up right now, but if you could tell us the specific model numbers your comparing, it would be of help. Honestly, the more expensive but slower Ghz ones are probably quad core, while the less expensive faster Ghz are probably dual core.
a b à CPUs
July 13, 2011 7:05:01 AM

Agreed, need specific examples please. Also remember that laptop CPU's tend to run at lower clock speeds due to the need for reduced power consumption.
a b à CPUs
July 13, 2011 8:03:59 AM

Slower clock i7 cost more than faster ones because the low voltage and ultra low voltage line of laptop cpu are special requirement for the market.

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a c 265 à CPUs
a b å Intel
July 13, 2011 3:30:10 PM
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1) As a rule, you get what you pay for. It is wise to look carefully at what you get.
How much ram?
How much hard drive space or a SSD?
Is there a more expensive discrete graphics chip involved?

2) A laptop is a package, do not look exclusively at the cpu that comes with it.

3) The cpu may be 2 core, 4 core, or 4 core with hyperthreading. The cost will go up as the capability increases. Unless you have known cpu demanding apps, the higher speeds may not be worth the price premium. Ditto for more than 2 cores.

4) As the core count increases, there may be less need for very fast cores. On a laptop, this trade off is made to increase battery time.

5) Do not focus on ghz as an exclusive performance metric. Current sandy bridge cpu's are perhaps 30% more effective per ghz than previous generations.
Similarly, current intel cpu's will be more effective per ghz than amd chips.

a c 188 à CPUs
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July 13, 2011 4:33:24 PM

Like others have stated there are a number of things that can play into performance on a processor today. In the market another area that can play a role in the pricing is TDP or thermal design power. In a laptop, HTPC and in a power consensus business environment the demand for very low power processors is growing. In the desktop board we have two difference types of processors shown with an “S” and a “T”. The “S” processors like the Intel® Core™ i5-2500S have a TDP of only 65w (so about a 1/3 less power than the Intel Core i5-2500. The “T” processors are designed for a HTPC environment and they come with a low profile HSF (heatsink/fan) they have an even lower TDP of 45w or 35w. So the Intel Core i5-2500K has a TDP of 45w and the Intel Core i3-2100T has a TDP of 35w. These processors have a great deal low TDP then the normal processors in the space but for the most part they should still be very close to the processors in the area around it in performance.

Christian Wood
Intel Enthusiast Team
July 13, 2011 5:37:32 PM


i7-2629M

2 / 4

2.10 GHz

4.0 MB



i7-2620M

2 / 4

2.70 GHz

4.0 MB


These two processors for example, the one on top is supposedly better
a c 265 à CPUs
a b å Intel
July 13, 2011 5:49:41 PM

You may be seeing what the customer will pay pricing from two different vendors.

Here is a link to the full 2629M cpu specs:
http://ark.intel.com/Product.aspx?id=54610
Here is the link to the 2620M specs:
http://ark.intel.com/Product.aspx?id=52231

you will note that the channel price for the 2620m is higher than the 2629.
That is because the 2620 has a faster clock speed, and better integrated graphics.

Most people will assume that higher numbered products are superior, but that is not the case here.
Chalk it up to marketing or consumer ignorance.

You are doing the right thing to look for answers.
July 13, 2011 5:53:43 PM

So what would be the downside to purchasing the 2620M?
July 13, 2011 5:56:04 PM

What about the 2720QM, what exactly does 4 cores get me that 2 does not (besides 2 extra cores). Essentially, what does that equate to in speed and processing?
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July 13, 2011 5:56:51 PM

collegestudent11 said:
So what would be the downside to purchasing the 2620M?



If ALL of the other specs on the laptop are the same, then none.
But I would expect to see some other differences to account for the price difference.
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a b å Intel
July 13, 2011 5:59:31 PM

collegestudent11 said:
What about the 2720QM, what exactly does 4 cores get me that 2 does not (besides 2 extra cores). Essentially, what does that equate to in speed and processing?



If your apps are multi core enabled, and can use more than two cores, then a quad is good. Unfortunately few apps can make use of more than two cores.

If you want speed you can really feel, look for a laptop with a SSD instead of a conventional hard drive.
July 13, 2011 6:02:46 PM

geofelt said:
If your apps are multi core enabled, and can use more than two cores, then a quad is good. Unfortunately few apps can make use of more than two cores.

If you want speed you can really feel, look for a laptop with a SSD instead of a conventional hard drive.



So I would be better off buying a laptop with the 2620M in stead of the 2720QM?

I am needing a fast processor for engineering software
a c 81 à CPUs
July 13, 2011 6:03:56 PM

collegestudent11 said:
What about the 2720QM, what exactly does 4 cores get me that 2 does not (besides 2 extra cores). Essentially, what does that equate to in speed and processing?


Greater scalability, more prudent multi-tasking and better performance in apps which benefit from more than two cores. So if you are just into regular browsing and some office work then a dual core will be fine. If you need gaming performance then a fast dual core is still good. If you need video editing/encoding speed and/or work in 3D content creation then a quad core is the way to go.
July 15, 2011 5:40:23 AM

Okay, I have it narrowed down to the followign laptop with either an i7-2620M (2.70 GHz with Turbo Boost 2.0 up to 3.40 GHz) or an i7-2720QM (2.20 GHz with Turbo Boost 2.0 up to 3.30 GHz)

-First of all, which would be better to maximize day-to-day performance for the laptop?

-and second, is this a good configuration for the laptop as a whole?



XPS 17

Memory
8GB Shared Dual Channel DDR3 Memory

LCD
17.3" FHD (1080p) with 2.0MP HD Webcam & Facial Recognition

Video Card
NVIDIA® GeForce® GT 555M 3GB graphics with Optimus

Hard Drive
1.0TB 500GB 7.2k HDD x 2

Integrated Network Adapter
Integrated 10/100/1000 Network Card

CD ROM/DVD ROM
Tray Load Blu-ray Disc BD-Combo (Reads BD and Writes to DVD/CD)

Sound
JBL 2.1 Speakers with Waves Maxx Audio 3 + Creative SoundBlaster X-FI MB 1.2

Wireless Plus Bluetooth
Intel© Centrino© Advanced-N 6230 and Bluetooth 3.0

Battery
90 WHr 9-cell Lithium Ion Primary Battery



a c 96 à CPUs
July 16, 2011 12:58:44 AM

collegestudent11 said:
I am buying a pc for school, and I was wondering why some of the intel core i7 processors get slower as they increase in price? (GHz)


That's because there are two different lines of Core i7 CPU. The most expensive ones are 6-core units, whereas the lower-priced ones are 4-core units. Processors today all have their clock speed limited because of heat production, and thus a CPU with more cores will produce more heat than a comparable CPU at the same clock speed with fewer cores. Thus, CPUs with more cores have to be clocked lower than CPUs with fewer cores to fit in the acceptable heat production limit (roughly 130-150 watts.) The reasons the higher-core-count CPUs are more expensive are because 1) some people will pay that premium for those chips, and 2) the 6-core units use more silicon and have more transistors, so they are simply more expensive to make as they use more silicon and have a higher production error rate (resulting in a lower percentage of salable CPUs) due to their larger size than the smaller quad-core CPUs. CPUs also have a variance in how much voltage is required to hit a certain clock speed, and a CPU with more cores has less of a voltage range to play with than a lower-cored CPU does because more voltage = a lot more heat and a high-core-count CPU already is putting out a lot more heat than a lower-core-count CPU. So, you need the best dies to make the high-core CPUs whereas you can use lesser dies to make quad-core CPUs and not have them overheat.

The old adage of "good, fast, and cheap- pick any two" certainly applies here:

- You can have a CPU with a lot of cores with a low price. It would have multiple CPU dies, since as die size increases beyond a certain point (roughly 250 mm^2, or a current 4-6 core CPU), yields drop off sharply and the price of a fully-functional CPU rises accordingly. It would be clocked at a low speed so that relatively poor dies that require a lot of voltage can be used without exceeding the desired thermal limit. This is the methodology that AMD uses with CPUs like the Opteron 6128s I have in my workstation. It's a CPU that uses two quad-core dies clocked at a mediocre 2.0 GHz with an allowable voltage of a pretty high 1.30 volts, but it sells for only $266 and is usable in quad-processor motherboards. Intel's cheapest 8-core CPU uses one massive die and sells for $1334 and clocks in at 2.00 GHz.

- You can have a CPU with a lot of cores and a high clock speed, but it will cost a ton of money. A 6-core i7 running at 3.46 GHz costs $1000, an 8-core 2.67 GHz Xeon runs $2280, a 2.40 GHz 10-core Xeon costs over $4000, and a 12-core Opteron that runs at 2.5 GHz costs about $1500. Those are the cream of the crop of the big-die, low-yielding CPUs and you will pay dearly for them.

- You can have a CPU with a lot of cores and a (relatively) low price, but it will be very low-clocked. You will be using the absolute bottom of the barrel full-core-count dies with regards to voltage, and clock speeds will be kept very low to keep thermals within limits. CPUs like the Opteron 6168 are good examples as the 6168 provides 12 cores that work in quad-processor arrangements for about $700 (Intel won't sell you a 10-core unit for less than $2558) but it runs at a paltry 1.90 GHz. Ramping up the speed to 2.50 GHz will cost you roughly twice as much.
July 26, 2011 1:31:57 AM

Best answer selected by collegestudent11.
a b à CPUs
July 26, 2011 4:00:16 PM

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