Dual core processor question

June 11, 2008 11:49 AM

If I have a dual core processor at 2.40GHz that is running software that isn't designed to utilize both cores (such as some older games), would this be equivalent to running it on a single core processor at that speed (all other things being equal)?

I'm thinking about upgrading my computer, and I currently have a 2.54GHz single core processor. I'm trying to figure out if the above mentioned would be a worthy upgrade at face value, or if I'd need to figure out if a particular piece of software would make good use of two processors. A newer computer would have faster memory type and I'd also upgrade the video card significantly; but in the above case would the processor speed actually be slower, if an individual game wasn't designed to utilize both cores? Or are there additional advantages to the newer chips, besides splitting up the processing time, that would create a speed advantage?

posted by SpacemanStix to computers & internet (11 comments total)

ghz speed is not a good indicator of how fast a processor is.

If you considering getting the exact same cpu you have now, only dual core, then yes I think programs would run about the same, maybe a bit faster. I assume though that you are getting a newer processor, so even with single core applications it will be faster.
posted by meta87 at 11:57 AM on June 11

ahh now that i reread your question i see you are just upgrading, so possibly they would be similiar. Could you list the processor you have now and the one you are considering buying?
posted by meta87 at 11:59 AM on June 11

A dual core processor will not speed up things that cannot be parallelized. However since most of the time you've got lots of stuff running, I think you'll still reasonably see at least not a penalty.

Depending on what your 2.54ghz processor is, you might also get more stuff-per-clock; the P4's were slower per clock-cycle than the core duos are (also slower than the P3's were!)

You could probably find benchmarks for your specific processor and the one you're considering, for all kinds of performance questions.
posted by aubilenon at 12:01 PM on June 11

The advantage is that while your game is using one core, your OS can make use of the other. So, if you're playing The Witcher, decide you want to look up something online in the walkthrough, you hit the windows key, launch your browser, find your cheat, and then alt-tab back to the game.

You can do it with a single core cpu, but it's pretty seemless with a dual core.

I just bought this guy for $99 with free shipping. Details are in this FatWallet thread.

Quoting another Fat Wallet user:

"The apps that can be effectively run on a quad core aren't one's you would use in every day life. Catia, Unigraphics, Solidworks, Maya stuff like that. Difficulty in writing the code goes up as the nth degree where n is the number of cores. A quad core is 8 times harder than a dual core. IBM's head of software development and EETimes The biggest topic at SC'06 and '07 was the multicore coding issue. Unless you have lots of programmers and lots of money (think the US Dept of Energy) writing code beyond dual core isn't generally possible. Good paper on how it is done and note that Berkeley got two dual core Opterons to go faster than two quad core Intel. IEEE best paper award The problems they address don't go any further than 8 cores."

That's specific to quad-core vs. dual-core, but it's in line with what you're asking.
posted by wfrgms at 12:02 PM on June 11

Thanks for the feedback. I'm currently using a Pentium IV 2.54Ghz processor, and I've officially upgraded my computer to the end of its lifespan (and a bit beyond). I'm looking at this: Intel® Core™2 Duo Processor E4600 (2.40GHz, 2MB L2 Cache, 800FSB). It's definitely on the affordable end of things. I'd like to have a bit of a performance advantage if possible that would make it worth the upgrade, but I suppose my video card and memory type upgrade would play a significant part as well; I'm just not sure how to judge the processor speed, taking those into account as well.

You could probably find benchmarks for your specific processor and the one you're considering, for all kinds of performance questions.

That's a good idea. Are you aware of any good online resources that would do this?
posted by SpacemanStix at 12:25 PM on June 11

I'm thinking about upgrading my computer, and I currently have a 2.54GHz single core processor.

Let's assume thats a pentium 4 at 2.54. Look at this list of benchmarks and compare it to a core 2 duo of the same speed. Yep, the c2d is many times faster at the same speed. Its architecture is different from the p4 and allows more work to be done by cycle.

Windows will try its best to balance the work between the two cores for apps that are not written to be multithreaed. In the case of older games I would imagine the main game process will reside on one core and some other stuff (OS functions) will go on the other.

I cant think of any scenario in pc gaming where an old P4 architecture will ever outperform the c2d, even as a single processor. It will always be faster.
posted by damn dirty ape at 12:29 PM on June 11

Here's a follow up question:

After reading up a bit, my understanding is that the new processors are able to perform more calculations per clock cycle, meaning that a newer processor can significantly outperform a pentium 4, even if the ghz were identical. Is there anything out there that will show functional equivalency between older and new chips? For example, what a 2.54 P4 would correlate to in processor speed on a newer chip?

This is probably the single issue that throws me off every time I think about upgrading.
posted by SpacemanStix at 12:31 PM on June 11

There's quite a bit of information available online about CPU speed comparisons, unfortunately there's not a lot of places that have it all in one place.

I'd recommend Tom's Hardware CPU Chart
posted by blue_beetle at 12:33 PM on June 11

Look at this list of benchmarks and compare it to a core 2 duo of the same speed.

And that's exactly what I was looking for. Thanks damn dirty ape.
posted by SpacemanStix at 12:33 PM on June 11

I'd recommend Tom's Hardware CPU Chart.

That'll help too. Thanks!
posted by SpacemanStix at 12:35 PM on June 11

If the game code is single-threaded, then, yes, the game code can only use a single core. Life isn't quite that simple, though. Consider; if you're running a game on Windows, Windows stays active (at a low priority) in the background. On a single core system it will be eating a few percent of the CPU to do that; on a multicore system, it can run on the other core.

Likewise, while the game itself may be single-threaded, some of the APIs it calls may be multithreaded or asynchronous and able to run on multiple cores - if it uses DirectInput for keyboard handling (for example), then the DirectInput code that watches the keyboard can run on the other core. Drivers may also be able to take advantage of the second core; again, if you don't have hardware accelerated audio, the sound driver may be able to use the second core for generating sound effects and music, freeing up more of the other core for game code to execute. Some graphics card drivers will be able to take advantage of a multicore environment, even if the game calling them doesn't.

So while your game code may never use more than one core, your system may be a bit quicker overall - likely no more than a few percent, though.
posted by rodgerd at 1:22 PM on June 11