Real-world microprocessor performance based on specs.

April 8, 2009 5:14 PM

Help me understand Intel Core 2 Duo processors. Wikipedia has a confusing chart that seems to indicate matching processor to the RAM is more important than the actual specs of the RAM or processor.

I'm buying a laptop on the Dell Outlet. But trying to do research for which one to pick has led me to the wikipedia page on Core 2 Duo processors. Several things confuse me.

1. What is the meaning of this "GB/s" unit of measure under the "Matched memory and maximum bandwidth" column? Is this a reliable indicator of generic processing power?

2. For DDR2 RAM, is the chart saying that the processors with only 533 FSB are always faster than the 800mhz processors? It seems so since they have more "GB/s". But that makes no sense! The processors with faster FSB should always be better... right?

3. Is a "Core 2 Duo" most likely better than a "Core Duo" or even a "Pentium Dual Core"? It would be helpful if I could narrow it down to just one processor type.


What should I be looking at when choosing a processor? I had it in my head that Core 2 Duo was the best dual core processor out today. If I choose the Core 2 Duo with the fastest FSB I can find, (assuming a reasonable clock speeed,) is that the way to go?

posted by brenton to computers & internet (15 comments total)

As it says in the part of the article you linked to: While DDR2 memory models with tighter timing specifications do improve performance, the difference in real world games and applications is often negligible.

So ignore the chart and just pay attention to FSB.
posted by zsazsa at 5:25 PM on April 8

" Is this a reliable indicator of generic processing power?"

That number measures memory bandwidth which is orthogonal to "generic processor power" as a measurement.

"I'm buying a laptop on the Dell Outlet.... What should I be looking at when choosing a processor?"

You're looking at low-midgrade mobile hardware from a vendor that sells whole machines. Given how little you understand about CPU power, I suspect for your usage you basically don't care about CPU power at all. Just buy the model with the nicest panel and feature set that you can afford, and then fill it with as much RAM as the chassis allows.
posted by majick at 5:40 PM on April 8

1. that's how much data the memory bus can transfer in a second. It appears to be irrelevant.
2. It does not say that, it says the opposite. The higher the FSB, the more data transferred per second.
3. Pentium 4 < Pentium 4 Dual Core < Core Duo < Core 2 Duo < Core i7
posted by gjc at 5:41 PM on April 8

It goes like this

Core i7 is the latest and greatest (not yet in notebooks)
Then Core 2 Duo
Then Pentium Dual Core
Then Celeron ____

For basic surfing/e-mail/media playback, anything > 1.6ghz Dual Core is probably good enough. The main thing I go for when I buy a notebook is LCD size and form factor, then probably LCD resolution.
posted by wongcorgi at 8:15 PM on April 8

We've reached a kind of plateau in the history of personal computing: no longer are the newest chips or architectures orders of magnitudes superior to the previous generation. At this point, it's just not possible to buy a slow computer (without buying a netbook or the like), and the difference between the very fastest currently available machine and the very slowest is a slimmer gap than it's ever been before. (I'm clearly talking about user perceived speed here, not the CPU's raw ability to crunch numbers--there are still differences if you're doing, say, real time video analysis.)

CPU is just not the thing to worry about on a laptop. Get the Core 2 Duo, but don't fuss too much over the details.
posted by Netzapper at 8:29 PM on April 8 [1 favorite has favorites]

Pentium 4 dual core is usually labeled 'Pentium D' or Pentium 4D.
posted by SirStan at 9:26 PM on April 8

Along the lines of Netzapper's comments about "perceived speed"...

Unless you are doing something mathematically intense (in which case you probably don't want a laptop), you're going to see much more values in areas other than the CPU. A lot of RAM (4 GB) and a fast hard drive (7200 rpm vs. 5400 rpm) with a large buffer will make more of a difference than the CPU ever will.

And for the love of all that is sacred and holy, when you first get it, wipe the drive and re-install the operating system without all the bloatware that Dell packs into computers. You'll see a huge difference there as well.

One last thought... I don't know what your budget/price range is, but looking at the link you provided, I don't think is too far out of left field. We (my co-workers and I) have been VERY impressed with "bang for the buck" on laptops from ASUS. NewEgg has quite a broad range of them, and that's what I'll be buying for my next laptop. One in particular brings Ferris Bueller to mind: "They are SO choice. If you have the means, I highly recommend picking one up."
posted by ElDiabloConQueso at 9:46 PM on April 8

"much more values"

sigh

"I don't think is"

double sigh

I fail at grammar and proof-reading, but hopefully that wosn't discredit me.
posted by ElDiabloConQueso at 9:48 PM on April 8

"Given how little you understand about CPU power, I suspect for your usage you basically don't care about CPU power at all."

Now that doesn't seem like a logical inference at all. Lots of people completely ignorant about all kinds of computer hardware need powerful hardware.

Since several people have brought it up, let me just say that I work in software and I can tell when I am being limited by processing power--and it happens to me often. My desktops have all been pieced together from parts found in trash bins, I'm a very frugal person, so in all likelihood, my laptop will be faster than my desktops. I use computers a lot for a lot of different things, and I'd like to know that I can do video editing or flash games if I want. Plus, if I do run XP, antivirus alone makes me want to have a fast processor.

"2. It does not say that, it says the opposite. The higher the FSB, the more data transferred per second."
...Are you sure? It looks like for DDR2 it is saying a T5200 @ 533mhz is 4.264 GB/s while a T9500 @ 800mhz is 3.200 GB/s. I admit that I don't understand the units, but isn't 4.262 > 3.200? I am still confused by this. Am I reading the chart upside down or something?
posted by brenton at 10:48 PM on April 8

While I still can't figure out why anybody would buy a Dell laptop, I'll answer anyway.

You're getting confused by the chart throwing in PC2-3200 memory, for some unknown reason, which is half the speed of PC2-6400 memory. (and the FSB's effective clock rate for those CPUs)

Compare the 4200, 5300, and 6400. Ignore the 3200. The faster FSB is always faster with matched memory, which PC2-3200 is not.

Basically it's saying that if you pair slow memory with a fast CPU, your transfer rate will be limited by the slow memory.
posted by wierdo at 1:08 AM on April 9

While I still can't figure out why anybody would buy a Dell laptop, I'll answer anyway.

You're getting confused by the chart throwing in PC2-3200 memory, for some unknown reason, which is half the speed of PC2-6400 memory. (and the FSB's effective clock rate for those CPUs)

Compare the 4200, 5300, and 6400. Ignore the 3200. The faster FSB is always faster with matched memory, which PC2-3200 is not.

Basically it's saying that if you pair slow memory with a fast CPU, your transfer rate will be limited by the slow memory.

FWIW, looking at the Dell Outlet, it looks like they're pairing DDR2-800 (aka PC2-6400) with a CPU that has a 1066MT/s FSB. For maximum performance, you'd want DDR2-1066 (aka PC2-8500)
posted by wierdo at 1:26 AM on April 9

Oops, sorry about the mostly double (now triple!) post. :(
posted by wierdo at 1:26 AM on April 9

" Plus, if I do run XP, antivirus alone makes me want to have a fast processor. "

It's smart to realize that some of the popular Windows antivirus tools have an effect on performance, but be aware CPU speed isn't really going to have a substantial effect on antivirus scanning performance. That's almost entirely an IO-bound operation.

" I'd like to know that I can do video editing or flash games if I want. "

Any CPU more recent than 2006 or so will give you more than enough power for casual video editing and flash games. Video editing -- not counting rendering work -- will gain a bit from not having the worst most abysmal memory bandwidth.

But seriously, if you're buying some random Dell you are by definition not caring all that much about CPU performance because whatever you get will be more than enough. Don't put anywhere near this much effort into it.

I get that you're caring about it more than you have in the past because you're not dumpster-diving for your hardware today, but that tiny amount of caring you are feeling right now is really very much not a serious or even primary concern for the transaction before you. That tiny amount of caring is analogous to the slender performance difference between the consumer-grade CPUs available new at market.

Nobody's going to try to sell you obsolete CPUs like a P4 Dual or a Core 1 Duo unless you're buying dumpster hardware again. As crappy as Dell is, they're not going to sell you a hamster-powered laptop. You'll pick up a C2D and it'll be plenty.
posted by majick at 7:00 AM on April 9 [1 favorite has favorites]

"You're getting confused by the chart throwing in PC2-3200 memory, for some unknown reason, which is half the speed of PC2-6400 memory."

Ah! Thanks, I didn't notice that! I'm an idiot. :D Everything makes sense now.

Everybody seems to agree that processing power is fairly unimportant for modern laptops, which is fairly confusing to me. Maybe what I had thought was processor limitations in the past can be chalked up to L2 cache or some other bottleneck that I'm not aware of.

Oh, and thanks to those of you who suggested other laptop manufacturers. The main reason I was going with Dell is because they have the outlet where occasionally there are really good deals, and also because I am able to search based on the hardware, though admittedly it's not as good as Newegg in that respect. Still, there aren't many laptops of any brand on Newegg for less than $500.

Does anyone know of another reliable place (eg, NOT ebay) where I can get used or heavily discounted laptops?
posted by brenton at 10:18 AM on April 9

Hard drive speed and the amount of RAM you have make the biggest difference these days, once you're on some sort of Core 2. The extra L2 cache on the ones that have 2 or 3MB per core will help for some things, but for most of the things you do on a day to day basis it won't matter.

My C2D T7400 is plenty for everything I ever do. It might be nice to have a faster CPU if I wanted to play crazy modern games, but I'd be more limited by the FireGL V5250 in my laptop than anything else anyway.

Really my biggest performance complaint is the 5400rpm hard drive, and even then I only really notice it on boot or when starting (but not while running) hogs like Photoshop and Lightroom.

As far as other places to look, I'm a bigot for (real..not the SL series, although I've got one coming for a friend in a few days and can tell you what I really think of them then) Thinkpads, so I suggest the Lenovo Outlet. It's not quite as easy to use, though. One nice thing is that Lenovo seems to be using DDR3 in all their T400 and T500 laptops. I think the T61, which you can still find a few of in the Outlet, uses DDR2, which is also fine, presuming it's matched to the CPU. DDR3 has a higher overall memory bandwidth, but also has higher latency, so it's slower in purely random access situations, while being much faster for sequential reads.
posted by wierdo at 11:27 AM on April 9