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Intel's Core i3, i5, and i7 processors present a headache-inducing combination of characteristics. I'll look at what matters and then dig a little deeper.

I was looking at some ads for various computers and noticed some confusing CPU info. For example:

  • Acer desktop with i5-650 @ 3.2GHz
  • SYX Gamer desktop with i7-950 @ 3.06GHz
  • Sony Vaio laptop with i7-740QM @ 1.73GHz

I always thought an i7 was better than an i5, which was better than an i3. Based on the above, is the Acer CPU better (as in more powerful, efficient, and faster) than either of the i7s? And why would one i7 (the SYX) be about 75% faster and more powerful than the Sony i7?

To call it confusing only scratches the surface of the processor nomenclature and configuration. In my opinion, it's more complex than mere mortals can comprehend.

Sadly, I am but a mere mortal.

However, I will share my priorities, which the average consumer may also have when selecting a computer. In so doing, I'm sure that I'll annoy some of the geekier members of my audience. Smile

I'll also look at a few more things that enter into the processor configuration mix and then compare the three processors that you list.

My take on what matters

For the average consumer, I focus processor selection on three things: cores, cycles, and cost.

"Unfortunately, it's not as simple as i7s being better than i5s, which are better than i3s."
  • Cores: By now, you've probably heard the term "core" being thrown about quite liberally. In a nutshell, a core is the working part of a processor - the CPU or Central Processing Unit. The CPU is the part that actually does stuff by following the instructions of the computer program that it's actually running.

    These days, most processors have more than one core or CPU on a single chip or package. This means that the processor can quite literally do two to four things at the same time. In a dual core processor, there are two CPUs. Thus, it can process two sets of instructions at the same time. A quad core has four CPUs.

    In Should I get a dual core or a quad core processor?, I recommend that you should get at least a dual core processor. There's no reason to get a single-core processor any more (if you can even find one).

  • Cycles: By cycles, I mean the megahertz or gigahertz (MHz or GHz) measurement associated with a processor. This is simply a measure of the raw speed of the processor. While often limited by other reasons, a 3.0Ghz processor is roughly twice as fast as a 1.5Ghz processor. (One gigahertz is 1000 or 1024 megahertz, depending on who you ask. A 500Mhz processor would be considered one third of the speed of a 1.5Ghz processor.)

    It's easy to fall into the "I want as much speed as I can get" trap. Unfortunately, the raw CPU speed plays only a small role these days in our common tasks like web surfing, video playing, emailing, and the like. You'd be hard pressed to notice the difference between a 1.5Ghz processor compared to 3.0Ghz, if that's all you do. On the other hand, if you do regularly perform CPU-intensive tasks, like video creation or other computationally heavy operations, you might well notice.

    Naturally, it's safest to get more than you need, but only within the limits of the next criterion.

  • Cost: The fastest, most capable processors will typically be significantly more expensive than models that are only slightly less capable. For example, on one random machine build-out that I examined, the difference between a 2.93Ghz and 3.06Ghz version of the same processor was roughly 10% of the price of the entire machine: a 10% cost increase for less than a 5% increase in speed. I'd be shocked if you'd ever notice the difference.

    The same goes for the number of cores. Technically, four cores are twice as fast as two, although other limitations make that a rarity. If the quad upgrade is comparatively inexpensive, it's an easy one to take. As the incremental upgrade cost rises, the choice becomes less obvious.

    Only you know your budget and your needs. When presented with the various options in speed, the thing to look at closely is the percentage performance gain that you might get compared to the cost.

I have to stress that my comments are directed at the average consumer. Clearly, if your needs dictate that you need more cores, you need the most cycles, or you're not sensitive to the cost, then you might as well need to make different considerations.

And, if you are that average consumer, it's pretty safe to stop reading here. In my opinion, you have the basics of what you need to decide what your next computer should have.

Other processor differences

There are many other factors that come into play besides cores, cycles, and cost.

  • Cache: Traditionally, a processor reads instruction from RAM one at a time. Processors have been getting faster and faster, but the speed of RAM hasn't kept pace. To compensate, processors "cache", loading blocks of RAM into faster on-chip memory. How CPU caching works is the stuff of both doctoral theses and nightmares; I don't have the first and I don't want the second. Suffice it to say that bigger is generally better and one of the differences between processors, even within the same "i" family, is the size of the cache that it uses.

  • Power Consumption: A faster processor uses more power. That part's pretty simple, but it's at odds with wanting to extend battery life in notebook computers as much as possible. As a result, many variants of processors are architected to use less power at the cost of some of the processor's other features. It might operate slower or lack other processor features.

  • Other Features: Other variations in processors include the type of socket used on the motherboard, the electrical interface used to connect to the other components on the motherboard, on-chip circuitry to perform graphics operations, the maximum amount of RAM that the processor is configured to accept, and probably more.

As you can see, there are a wide variety of combinations, which result in an incredibly wide variety of processors.

OK, but what about the i-mess?

Unfortunately, it's not as simple as i7s being better than i5s, which are better than i3s. You'll note that I ignored the whole i-mess in the discussion above. Unless you're a serious gamer or someone who really needs to tweak every ounce of whatever out of your system, the whole processor nomenclature is fairly irrelevant. (This is where the hardware folks heads explode. Smile) I just can't advocate the average consumer needing to take the time to understand it all.

If we do dive in just a little, the first thing to realize is that i3,i5, or i7 isn't enough to identify all the characteristics of the processor. You really do need the whole processor model number as you've provided. To be honest, I still couldn't tell you what makes an i3 an i3 versus an i7. There's a complex combination of features and technologies that go into the mix.

So, let's look at some basic characteristics of your three examples:

Processor Cores Cycles Cost Power Cache Max RAM
i5-650 2 3.2Ghz $176 73W 4MB 16GB
i7-950 4 3.07Ghz $294 130W 8MB 24GB
i7-740QM 4 1.73Ghz $378 45W 6MB 8GB

(Specs are from Intel's specific product data sheets: i7-950, i7-740QM, i5-650. Cost is "Release Price", per assorted Wikipedia articles on Intel processors. This is not meant to be accurate. It's provided for comparison.)

So, yes, that i5-650 is "faster" in GHz, but it has half as many cores as the i7s that you list. (Nope, not all i7s are quad core. It wouldn't be that simple, but the two that you mention happen to be).

The i7-740QM is clearly designed for the mobile market, given its significantly lower power consumption, probably due to its slower speed. (The trailing "M" in the CPU identifier is, indeed, an indicator that the processor is intended for the mobile market.)

Which is better?

Define "better".

Among these three processors, the i7-740QM is probably a better choice for a laptop if you plan to run on batteries frequently. The i7-950 might make for a good workhorse desktop machine and you might find the i5-650 in a lower end desktop.

But I use "probably" and "might" on purpose. The devil, as they say, is in the details.

And I'll bet that even he has a headache by now.

Article C4812 - May 7, 2011 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

Tony M.
May 10, 2011 8:54 AM

Another great article from Leo. I long for the days when processors had more-informative designations like 486DX-33 and 486DX-66, etc. Now, it's more clear than ever that the major chip producers are merely trying -- and succeeding -- to obfuscate their chips' real performance info. Without benchmark figures, it's all a wild guessing game.

Thanks, Leo, for confirming my long-time suspicions about this issue.

Carl R. Goodwin
May 10, 2011 9:05 AM

I agree with Tony-excellent article, and I too wish for the "old days". A good way for a person to know what it is in their machine is to run "Belarc Advisor"-it even states how big the cache is in the processor, as well as speed, etc..

Ray Tanguay
May 10, 2011 9:10 AM

One of the best, and easiest to read, summaries on i-3/i-7 differences. Makes choosing my new PC simpler. Thanks.

John Palmer
May 10, 2011 9:24 AM

To see the relative speed of most current processors from both AMD and Intel, take a look at PassMark Software's CPU Benchmark page:

E. Macmillan
May 10, 2011 10:57 AM

New 'Ask Leo' subscriber, but the articles so far have been extremely well-thought-out and easy to understand. I am wondering though, as someone who is a "serious gamer", is it more important to have higher speed or more cores, or does it not really matter?

Eoghan (pron. Ewan), 16, from Scotland

Both. Smile Honestly, though, it really depends on the games you plan to play. Not all make use of all cores. To be even more honest, the video card is probably a more important consideration for hard core gaming.

Digital Artist
May 10, 2011 11:54 AM

"Sadly, I am but a mere mortal."
Does this mean there is no Santa Claus? (I think I'll keep believing in you, anyway.)

May 10, 2011 12:23 PM

Using the Way-Back Machine to the 70's and 80's, there were mainframe MIPS wars - Millions of Instructions Per Second (or as we performance specialists called them - Meaningless Indicator of Performance). Why? Because each Mfgr had their own special mix of Complex Instruction Sets (CICS). Hence 1000 transactions per second benchmarks became into vogue to compare machines. (Hasn't changed much; see John P's reference above.)

Leo didn't mention why multi-core came about. Heat. Remember trying to hold a laptop in your lap and getting burned? Faster single core chips were hot. Desktops could cope with bigger fans or liquid coolant solutions but not laptops.

Multi-core CPUs are slower (cooler) per CPU but more throughput can be achieved when two programs can process side-by-side vs. being single threaded through one CPU. However, can you keep 4 CPUS busy with 4 programs? I can't.

In the 90's, the Mfgr's moved from CISC to RISC CPUs (see a wiki for definitions) and optimizing compilers. These compilers examined the source during compilation to look for independent sections of code that can be executed in parallel. Unfortunately, our daily use of computers - email, word processing, simple spreadsheets - a difficult to optimize.

So we're back to I3, I5 and I7 processor chips. If you do things that need 4 cores, then i7 is your choice; the rest of us can probably make do with i3.

As chip science moves forward, the i3 chips will be faster than the old x86 fastest chips but much cooler.

May 10, 2011 2:18 PM

Regardless of i3, i5 and i7 cores- how it's configured is an important consideration. A PC for business vs. media vs. gaming provide different benefits. Many retailers now show ratings (usually intel based PC's) on what it does and how well it does it. Ex: If your use is to deal primarily with media- and if it shows an i3 is "better" than a similar i5- it may very well be. So the choice of i3, i5, i7 may take a back seat to how well it's built/configured for your intended use. Just another consideration, a F.Y.I.

James Hillier
May 10, 2011 2:26 PM

"In my opinion, it's more complex than mere mortals can comprehend.

Sadly, I am but a mere mortal."

Love it.....absolutely priceless!!!


May 10, 2011 7:12 PM

7 years ago when I bought my current HP Pavilion notebook I was doing mainly web surfing, which is what I still mainly do. I did not think I needed the higher priced Pentium III processor model, so I got the 2.88 MHz Celerion processor. Everything has been fine for 7 years.
Just recently I purchased an HP Photosmart All-in-One printer/scanner. The documentation shows my HP Pavilion XP/SP3 notebook should be good enough. But on large print jobs the time to print is bad! If I had put out the extra money for the Pentium III processor maybe the printer/scanner I bought would work better now.

Since I keep computers for a long time, when purchasing my next computer I will put out the extra money for the bigger/faster/better model so I will be covered for whatever future demands may bring.

Dave Toombs
May 10, 2011 8:55 PM

A couple of months ago I bought a 64bit Win7 desktop. I do a lot of personal video editing plus a couple of projects for SETI and Sloan Sky Survey. I have an i5 650 with 4 cores/processors. What this means essentially is 2 core duos giving the 4 cores for 64bit operation. the 650 by itself is a 2 processor chip "core duo". The 64bit would be a "Core duo 2". That's my story and I'm sticking with it!! Unless I'm wong which has never happened.............?

Dave Markley
May 11, 2011 10:50 AM

I just wanted to clarify some points about the "I" -core processors. If your buying a new PC or just CPU, make sure you get the 2nd generation (Sandy Bridge Edition), which are much better than the original I-cores. Secondly, I just bought a new Dell with an I-5 CPU and it IS a quad-core processor. The 2nd generation I-5, depending on the model can be dual- or quad-core. Mine, for example, is a 2.3 ghz with turboboost and a 6 mb L2 cash.

May 11, 2011 1:56 PM

Couple of points I like to see made:
- Intel already multi-tasks the CPU, meaning that a core or CPU can run more than one task at the same time

- another comment already made the point that the average user cannot keep even a 2 core CPU busy, let alone a 4 core (or more in near future). The simplest way to find that out is start Task Manager and minimize it. A small icon appears in the Task Area. Most of the time, 90%+, it will be dark grey, meaning the CPU is basically idling along (ie you don't need more CPU cycles on new machine)

- for new purchases, start looking looking for USB 3. It provides much faster USB access, which is important for external devices, like TB disk drives. I've already seen a few USB 3 external devices and I've seen USB3 offered as a $20 upgrade. Well worth the price.

John Bennett
May 12, 2011 2:08 AM

Re cache: Cache is very high speed memory. Trying to put it simply, an instruction or piece of data used recently is likely to be needed again soon, so a copy is kept in cache. If the required data is found in cache that's called a hit and it is accessed quickly, if not, it is loaded from ram and copied to cache. You need to look at the theses for algorithms for how long to keep it in cache. The hardware aspect involves stuff called content-addressable-memory. (I think that's enough for a simple explanation).

David from Brevard
May 13, 2011 9:43 AM

Intel processors are fast, buy I think AMD processors generally give me more bang for the buck. I'd like your take on the AMD v Intel question. Or should I ask this one level up, perhaps?

Much like the whole i3,5,7 discussion, I actually pay very little attention to AMD vs. Intel, and I think that by-and-large the original factors I list for average consumers is more important then brand. Naturally those who are more deeply invested in squeezing every possible ounce of performance out of their processors will have opinions, but a) that's not me, and b) it's not something the average consumer needs to worry about.

Jim H
May 14, 2011 12:42 AM

My i7 980X 3.3 GHz is 6 core and with 24 GB RAM I love it! It's also liquid cooled...

June 16, 2011 5:22 PM

What is the difference between Intel core i5 and Intel dual core i5.? which is faster?

January 4, 2012 11:42 PM

I3 3:20 bdr 6x burn time I5 1:15 burn time 6x bdr I7 40:00 min burn time 6x bd-r usb 2.0 480 mbps bottom line faster blueray editing more cores more task per second tick tock
I7 2.0ghz turbo 2.9ghz the clock is faster in the I7 everytime unless yotta a 2.5 float China will always keep us in the stone age

January 8, 2012 12:22 AM

Advantages of i5 over i3
& i want to purchase a laptop(I will use it for developing new software and website which would give me a reliable performance in a affordable price)

plz reply soon

frederick w. graves
January 12, 2012 9:47 AM

i,m, 59 yrs. old & know just enough about computers to be dangerous. if you understand what i mean. iv,e had 5 heart attacks & do have a hp desk top. iv,e been looking into getting a laptop. just so i don,t have to get off the sofa as much. i,m confussed about what laptop to get. iv,e looked all over from walmart to others. i don,t know why but i have it in my mind i want a laptop with a blu ray device, 640gb, a 15" to a 17". all i have is time. i,m on social security so i have to watch how much the cost may be. maybe you can come to my rescue. HELP ME PLEASE. just kidding.

January 12, 2012 12:24 PM

Here's an article where Leo discusses his choices in getting a computer.
What computer should I get?

February 6, 2012 10:39 PM

i wana buy laptop!!!!!!!!
(HP) i3 500GB Hard disk,4GB Ram,1GB Graphics card +whatever is in laptop.......
it cost me 31,000rs(Indian currency)
should i buy it r should i buy i5???????
i mainly have 2 use it 4 study nd gaming purposes.........
games like god of war 1,2,3 OR call of duty..........

February 6, 2012 10:42 PM

i wana buy laptop!!!!!!!!
(HP) i3 500GB Hard disk,4GB Ram,1GB Graphics card +whatever is in laptop.......
it cost me 31,000rs(Indian currency)
should i buy it r should i buy i5???????
i mainly have 2 use it 4 study nd gaming purposes.........
games like god of war 1,2,3 OR call of duty..........

April 27, 2012 4:32 PM

Thanks a lot for this article! I'm quite experienced with computers but I never quite understood the whole core, Ghz and i7 thing until now.

April 29, 2012 4:49 PM

Thanks so much for this article. I'm about to buy a laptop and was wondering if it's really important for me to spend the extra hundred or two for an i7 processor compared to an i-5. I plan to do graphics and web design ultimately so your article helped me on the final decision. Thumbs up!

Md Rafique
June 22, 2012 9:23 AM

1) how can i run fast my windows ? is it depend on configuration of desktop or window ? i need help..

2) in budget of 15000 INR what is best cofiguration of CPU for me ?

June 22, 2012 6:49 PM

This is the best explanation I have seen yet! Thank you for breaking it down for the average guy.

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