Guest
skaertus
2010-07-09T13:17:07Z

I am planning to buy a new laptop this weekend, and I want a desktop

replacement - just tired of small screens and low performance, and,

unfortunately, I simply do not have a desk to put a high-end desktop. If

I was to buy a desktop, it would certainly be equipped with a Core

i7-860 2.8 GHz processor. While I cannot replicate such power in a

notebook, I am trapped in a dilemma of choosing between four cores or a

high clock speed. In a desktop, it seems to me that such dilemma does

not exist, since the processors can use more power and have higher clock

speeds: it would be worth more to have a 2.66 GHz or a 2.8 GHz

four-core than a 3.2 GHz or a 3.33 GHz dual-core. But in laptops, it's a

completely different story.


The contenders are basically the Core i7-620m and the Core i7-720QM (or

the i7-740QM), and the runner-up is the Core i7-820QM (and i7-840QM), if

it is really worth it.


I have done extensive research on the Internet. The sources are not

many, but it led to to some conclusions.


The Core i7-720QM 1.6 GHz has 4 cores and 8 threads, but a low clock

speed (1.6 GHz) that can be increased up to 1.73 GHz with all cores

operating. It can go as high as 2.4 GHz with only two cores. The Core

i7-620M, on the other hand, has a clock speed of 2.66 GHz, which can be

increased up to 3.06 GHz with Turbo Boost using all cores.


Theoretically, the i7-720QM would be a superior processor. Intel has put

a higher number to identify it (7 instead of 6... duh...). Four cores

operating at 1.6 GHz equals to 6.4 GHz (in the case of i7-720QM), while

two cores operating at 2.66 GHz equals to only 5.33 GHz (in the case of

620M); with Turbo Boost, the i7-720QM would sum it up to 6.92 GHz and

the i7-620M to 6.12 GHz - still a big gap in performance. In addition,

the i7-720QM has 6 MB L3 cache while the i7-620M has 4 MB. But that's

just theory. In real life, things are a little bit different.


I do have a Core 2 Duo right now and I see Windows making extensive use

of the two cores. However, I suspect that even the most advanced

software are not 100% optimized for multi-core and multi-threading

processing. A clock speed of 1.6 GHz could be a disadvantage in this

scenario, especially comparing to the much higher clock speed of the

i7-620M. The i7-620M has a clock speed which may be 1.33 GHz higher than

the Core i7-720QM, and that seems to me a big difference.


I've read that the i7-620M would be better for single-threaded or

lightly multi-threaded applications, due to its higher clock speed. Some

sources say that the i7-720QM would be the better choice for heavily

multi-threaded apps, while others say that, due to the huge difference

in clock speed, the i7-620M would be the winner even in those cases.


There are other factors which must be taken into consideration, of

course. The i7-720QM has 6 MB of L3 cache, while the i7-620M has only 4

MB, and that makes a difference - however, I do not know whether this

additional 2 MB make it up for the huge gap in clock speed. The i7-720QM

also supports 1333 MHz memory, while the i7-620M supports only 1066 MHz

memory, and I do not know how this will affect the performance - some

sources even say this is irrelevant.


The i7-620M is a 32nm, 35W, processor, and consumes less power than the

45nm, 45W, i7-720QM. It means less heat and more battery life, of

course. But, in terms of performance, less heat and less power

consumption could mean that the i7-620M could achieve its top Turbo

Boost performance more easily than the i7-720QM. As a result, it would

be more likely for the less-power hungry i7-620M to achieve the 3.06 GHz

Turbo Boost performance than the i7-720QM to achieve the 1.73 GHz.


I've seem some benchmarks on the Internet. In Passmark Software's

website, the Core i7-720QM scores higher than the i7-620M, but I am

afraid these numbers reflect a theoretical performance that nobody will

ever get to achieve in day-to-day situations. Notebookcheck has done

some comparison too and it ranks the i7-620M in a higher position than

the i7-720QM. The i7-720QM scored higher than the i7-620M in most tests,

but Notebookcheck thought the i7-620M would be a superior processor -

perhaps it thought the i7-620M would be faster in real-life situations.


I have not yet come to a conclusion. I am leaning towards the i7-620M,

as it would be a faster processor than the i7-720QM in most situations. I

suspect I do not use very multi-threaded applications; however, I do

extensive use of multi-tasking. It is very often to me to keep Microsoft

Office applications, a web browser, a multimedia player, Adobe Reader

and other applications opened simultaneosly. And I like them all to run

very fast all the time...


Now that I have done this research and that I still can't reach a

conclusion, I would like some help. Are the conclusions I came up with

(above) correct? Which of these processors would be faster and which one

would be the better choice? And how these processors would compare to

mine (a Core 2 Duo T8300 2.4 GHz)? Thank you for the help!

Sponsor
Der Meister
2010-07-09T13:43:16Z

the 720 will be the faster. but what are you doing with it? that will make the difference between the 620 and 720... If you just do what you said "MS office, web browser, media player, adobe reader, and a few other applications". I would suggest an i5, and get a better battery life. You wont see any difference for what you are doing between the i5 and i7...

skaertus
2010-07-09T14:21:38Z

Thank you for your prompt response.

In fact, I do not intend

to use the laptop for video editing or any other application such as

that. However, I am very picky in what regards CPU performance and I

have always demanded a lot of computer power by heavily using normal

applications. I usually keep Firefox, Chrome and Internet Explorer

opened, each one with more than 10 tabs opened. I use Microsoft Word

with very large documents, about 300-500 pages, and filled with hundreds

(sometimes thousands) of Endnote citations each one updating

automatically every time I change one of them, and I found this to be a

very demanding task that a high-end Core 2 could not handle properly

(perhaps Endnote is not the best-engineered software in the world, but I

can't do anything about it...). I also use extensive OCR in hundreds of

50-page documents - also a task that demands a lot of processors. In

addition, I would like to use the laptop for some gaming (occasionally -

but I am not really worried about this, because the video card will

probably be an ATI Mobility Radeon 5870) and other stuff.

I would agree with you that a Core i5 processor would be more

than enough for general use such as the one I described in the previous

post and a Core i7 would be overkill. However, I currently have a laptop

with a Core 2 Duo T8300 2.4 GHz, and I find it to be slow and sluggish

and I would really like a radically faster processor. In this scenario, I

am pretty sure that a mobile Core i5 would not be enough for my needs. I

would be ready to buy a high-end desktop, but I simply have no place to

put it. So, the options I have are the mobile i7, I would like to know

how real-world performance would be with a Core i7-720QM and a i7-620M,

since, due to the reasons I explained in my previous post, the four

cores and large cache would make it up for such a huge difference of

clock speed.

fat78
2010-07-09T14:33:48Z

 i7 for a laptop is more for gaming, designing,  or some one who just likes having the best stuff. Isnt realy need for basic programs 

(Also cpu cache dosnt increase clock speed it just reduces time length of accessing memory.)

fat78
2010-07-09T14:39:44Z

how slow is it right now? might be that you have alot of crap on your computer slowing it down

skaertus
2010-07-09T15:03:42Z

Although I know that a Core i7 is not intended for general use, I may

fall into the category you mentioned of "someone who just likes having

the best stuff". I like my computers to be very fast and responsive.

I

have formatted my computer about two months ago for the last time.

There is no crap on it, and I don't like installing too many programs to

avoid slowing it down. I even put some "portable" version of some software to avoid having to deal with slowdowns caused by modifications on the Registry and on DLLs. The CPU would be OK for general purpose usage,

but I am very picky about performance, and I wish the processor was much faster...

Der Meister
2010-07-09T15:21:04Z

A i5 will be loads faster than your T8300. I biggest thing against your i7 wants is that none of the applications you are running will use the multi core. So a i5 540 will more than meet your needs and out perform the i7 for all the applications you will be running... As for your computer running fast an responsive you would see under .1 of a second difference between the two. If you really want a speed jump get an SSD.... 

skaertus
2010-07-09T16:13:01Z

Thank you. So it seems a dual-core with high clock speed is better than a quad-core with lower clock speeds in what regards laptop computers... I've seem some reviews of the new AMD Phenon II X6 and the conclusion was that it was theoretically faster than a quad-core Core i7 desktop processor; however, in day-to-day use, the i7 would be faster and the X6 would be better if the user had the specific need of 6 slower cores instead of 4 faster cores. The same conclusion seems to apply to dual-core and quad-core laptop i5/i7s, right?

Still, in the model I am looking at, there is no option for a Core i5-540M. And the price difference between the dual-core Core i5-520M 2.4 GHz and the dual-core Core i7-620M 2.66 GHz is small, so I think the 266 MHz and the 1 MB L3 cache in the i7-620M are worth paying a small premium. What it seems is that the dual-core Core i7-620M is faster for my kind of use than the quad-core i7-720QM - at least, that is what I understand from your message. Is that so?

Now, I would like the SSDs, and I know they are fast, but they are also very expensive, and I cannot afford to buy it right now. Instead, I'm going with two 7200 RPM HDs (one for the operating system and the programs, and the other for the documents, music, videos, etc.), expecting this combination to deliver better performance (and also a reasonable storage) than my 5400 RPM HD...

Der Meister
2010-07-09T16:18:52Z

I did see the 620 as a good performer as well though it does suck some more battery than the 540. But if you cant get the 540 then the 620 is a good choice then. And the 7200rpm drives are much better then 5200 rpm drives 

skaertus
2010-07-09T16:28:47Z

Thank you. In fact, the i7-620M and the i7-720QM are nearly the same price in the laptop I am looking at (and that's the whole point of my post) - but it seems that for my pattern of use, the i7-620M would be the faster option due to higher clock speeds - at least, this is what I got from all the posts...

I don't care about battery in this specific laptop. It will be a 17" desktop replacement which I don't expect to carry around and which I am only buying because I have no place to put an actual desktop. I already have an unexpensive smaller laptop which does not suck too much battery and is very light to carry, but it has a slower processor and an integrated video card - this is the one I go to the streets with.

fat78
2010-07-09T17:04:37Z

Well the amd 1090t has turbo core with it so the idle cores most programs dont use arnt slowing down the cpu to much

AKwyn
  •  AKwyn
  • 71.2% (Friendly)
  • Advanced Member
2010-07-10T15:02:03Z

if you're looking for something similar to that then the Core i7 processors have something called Enhanced Intel SpeedStep Technology that does basically the same thing that fat78 described.