Dual-Core Processor question

FatCobra · Post by **FatCobra** » Thu Aug 28, 2008 6:47 pm

I'm building a new gaming computer in the near future, I'm confused about the speed ratings of dual-core processors, mainly the speed in Ghz.

I have a laptop with Intel Mobile Dual Core rated at 1.66Ghz. Since that's two cores, does that mean each core is 1.66MHZ, or they add up to that? If it's 1.66 Ghz per core, can they work together and combine that into 3-something Ghz?

Man, it was easy with single core processors, the higher the number, the better.

Maybe somebody more tech-savvy than me can explain how dual-core processors work and what's a good processor for a gaming pc build?

kernow · Post by **kernow** » Thu Aug 28, 2008 7:04 pm

The cores are 1.6GHz each yes, but they don't add together to make 3.2GHz, they allow software threads of execution to run concurrently, most software, like your Operating system and applications is heavily multithreaded so it would multitask better using a dual core machine, with games they are to a certain extent but work is being done to make sure they will be more dual core capable games in future.

If I was to build or purchase a modern gaming PC, I'd choose the fastest dual or quad core I could purchase, probably a dual core 3GHz. That would suffice for gaming and other uses.

With quad core you wouldn't see much of an advantage for normal use, or games at present. Also a decent graphics card is paramount for gaming too.

captpain · Post by **captpain** » Thu Aug 28, 2008 7:10 pm

^^ What he said ^^

Also, now is not the time to buy a quad-core processor. You can't future-proof a computer. By the time quad-core processors are actually taken advantage of, those which are currently on the market will be obsolete. Go for a dual-core.

Aleanil · Post by **Aleanil** » Thu Aug 28, 2008 7:10 pm

Dual core processors are simple, you have two cores! It's like multi-processing of old, except now it comes on a single processor chip.

Basically, to extend your example, you have 2 processor cores, each running at 1.66ghz. Each application you run generates a 'thread', which runs on one of the cores. Thus, if you run multiple programs at one time, it will split processing them between cores. In theory, it means you have almost double the power of a single core processor. In practice, if you're running a single application and you want it to take advantage of both cores, it must be multi-threaded for it to use both cores at once. For multitasking and for regular computer usage dual core processors are absolutely wonderful.

In short, it's a good thing to have the multiple cores, but for some specific apps it's still more powerful to have a single, higher speed core (as the application can't take full advantage of multiple cores). However! I am unsure how this impacts gaming today or offer you any suggestions on what to buy, I haven't done pc gaming in many years

Hope that makes some sort of sense!

bay · Post by **bay** » Thu Aug 28, 2008 7:17 pm

as a developer i love my quad core.

as a gamer or a normal computer user, you won't notice it, and it probably won't even be effectively utilized.

captpain · Post by **captpain** » Thu Aug 28, 2008 7:20 pm

bay wrote:as a developer i love my quad core.

as a gamer or a normal computer user, you won't notice it, and it probably won't even be effectively utilized.

Well, yeah, I meant for "normal" people

Very close to nothing that most people will encounter takes real advantage of it at the moment, and won't for a long time.

trivial · Post by **trivial** » Fri Aug 29, 2008 12:08 am

Nothing as cool as Windows XP x64 is coming that will only work on more ways than dual. (Don't ask me about x64 app compatibility. I keep games forever but discard apps without provocation.)

I've been waiting over a year to build a sys with Nehalem CPU, but since gaming benchmarks have been released I think it's finally time to build an E8600 system instead.

ReKleSS · Post by **ReKleSS** » Fri Aug 29, 2008 2:42 am

CPU speeds are only really good for comparison between CPUs of the same family... bigger numbers don't always stand for much. My previous cpu (5-6 years old, I think) was a pentium 4 clocked at 2.0ghz, yet a single core of my Q6600 (2.4ghz) could probably achieve at least double the performance.

Gaming and number crunching benchmarks are probably the way to go. There's probably some way to make sense of Intel's CPU numbering scheme, but I never really looked.

MR_Soren · Post by **MR_Soren** » Fri Aug 29, 2008 12:01 pm

Reckless speaks the truth. Clock speed comparisons are only good within the same processor family due to different architectures.

For a simplified example, suppose you have a 1 Ghz processor that can multiply in four clock cycles and an 1.5 Ghz processor that can multiply in seven clock cycles. The 1Ghz processor can perform more multiplications in a second than the 1.5Ghz processor.

That's why you need to benchmark processors for specific uses to see which is best.

Most games still run on a single core, so the extra core(s) don't currently mean much to a gamer.

Ex-Cyber · Post by **Ex-Cyber** » Fri Aug 29, 2008 12:27 pm

kernow wrote:most software, like your Operating system and applications is heavily multithreaded

I'm pretty sure that most programs are single-threaded. Common operating systems effectively will be multithreaded, partly because of kernel-level threading, but also because a modern OS consists of many separate programs running at the same time.

kernow · Post by **kernow** » Fri Aug 29, 2008 12:31 pm

I'd imagine something like firefox would have more than one thread, at least one for background work and one for the interface to keep it responsive.

Ed Oscuro · Post by **Ed Oscuro** » Fri Aug 29, 2008 8:43 pm

I would be cautious about buying a quad core unless I had a 10K or 15K RPM hard drive and ultrafast RAM.

That said, if you stick with the same machine for years, you won't mind the extra performance. If you're worried about price or energy efficiency, though, dual core has the right price point.

Edit: also Firefox should run only one thread

The thing people have to realize is that writing multi-threaded software sucks.

moozooh · Post by **moozooh** » Fri Aug 29, 2008 10:41 pm

I'm still waiting for that inverse hyperthreading. That is, when multiple separate cores add the performance up to one. That would make the difference in performance between, say, a dual-core and triple-core pretty huge (compared to almost nonexistent as it is today).

ReKleSS · Post by **ReKleSS** » Sat Aug 30, 2008 12:30 am

moozooh wrote:I'm still waiting for that inverse hyperthreading. That is, when multiple separate cores add the performance up to one. That would make the difference in performance between, say, a dual-core and triple-core pretty huge (compared to almost nonexistent as it is today).

My first response to this is "I don't think so". If you have an inherently linear task there's not much you can do with more cores to make it go faster, unless you go for massive branch prediction like intel did with the P4. Not a good idea in general.

EDIT: Think of the analogy about making a baby in 9 months vs impregnating 9 women.

For running Gentoo Linux, four cores is awesome. For a little while I was compiling stuff just to watch it fly by. Most of the time my cpu is near idle, but there are times when having a quad core CPU pays off. If you can find a good value quad core CPU (the Q6600 was excellent a year ago, dunno about now) you may as well go for it.

captpain · Post by **captpain** » Sat Aug 30, 2008 12:43 am

ReKleSS wrote:
moozooh wrote: For running Gentoo Linux, four cores is awesome. For a little while I was compiling stuff just to watch it fly by. Most of the time my cpu is near idle, but there are times when having a quad core CPU pays off. If you can find a good value quad core CPU (the Q6600 was excellent a year ago, dunno about now) you may as well go for it.

Keep in mind this is for gaming... Right now, the dual-core processors are unbeatable for price vs. performance in gaming (and will be for quite some time).

TLDragoon · Post by **TLDragoon** » Sat Aug 30, 2008 1:01 am

Looking at some prices, I'd definitely go with a dual-core. Dollar for dollar, you'll get more bang for your buck since very few games that I recall are actually quad-core capable, while more and more are making use of 2 cores.

That being said, I might trade off a little on the processor to get a faster graphics card, if your budget is tight.

trivial · Post by **trivial** » Sat Aug 30, 2008 2:17 am

Ex-Cyber wrote:Common operating systems effectively will be multithreaded, partly because of kernel-level threading, but also because a modern OS consists of many separate programs running at the same time.

Are affinities elective?

They can be. But a computer ought to handle this kind of prioritization task better than a human being, right?

So how do you elect to maximize snap, which is one of the things Ed's getting at with his low-latency hard drive idea, except by giving undeserved timeslices to the foreground app's process(es)?

If it were to come down to hardware and O/S selection for the end user, exactly how would snap best be served? By selective introduction of "obsolete" products? Are there better rules than the ones experience imparts to human beings of limited snap?

ED-057 · Post by **ED-057** » Sat Aug 30, 2008 4:20 am

I would be cautious about buying a quad core unless I had a 10K or 15K RPM hard drive and ultrafast RAM.

To go for a quad, I think you'd have to have a particular task in mind that was multi-threaded and probably interactive as well. Compiling would be one, since you'd want to run/debug the result ASAP right? But for the occasional batch type operation like transcoding a video, you might be better off just putting a separate PC to work on it while you keep playing games or whatever on the other. Power-wise I'm not sure how it'd work out since extra cores probably don't use that much energy if they aren't doing anything. They still cost more though.

As for hard drives, I would go for two drives of modest size and speed (though larger buffers are a plus) rather than a single huge, power-hungry, high (spindle-) speed drive. If one of them dies you don't lose all your stuff at once. And on the performance front, if you're archiving a crapload of files for instance, it will run faster with the source files being on one drive and the output file on the other, compared to reading and writing from/to the same drive which would need to seek back and forth.

moozooh · Post by **moozooh** » Sat Aug 30, 2008 9:56 am

ReKleSS wrote:My first response to this is "I don't think so". If you have an inherently linear task there's not much you can do with more cores to make it go faster, unless you go for massive branch prediction like intel did with the P4. Not a good idea in general.

By that, you mean it's not possible to implement well, or just don't see the point?

ReKleSS · Post by **ReKleSS** » Sat Aug 30, 2008 10:15 am

moozooh wrote:By that, you mean it's not possible to implement well, or just don't see the point?

If someone were to pull it off it would be valuable, because single-threaded programming is easier, and constantly turning up cpu speeds can't go on forever. I'm just not sure it's possible to implement at all.