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Gaming PC - which processor should I get?


azagahl
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>The reason why a Athlon X2 3800+ might be slower than a Athlon64 3800+ is because the 64-3800 is clocked higher. Each of the two cores in the X2 will be clocked slower, but AMD gives it the "3800" rating because the second core "makes up" for the lower clock speed.

When you write X2 3800 vs. 64 3400, I think from the point of view of a single thread and see 64 1900 vs. 64 3400. I'm assuming that an "X2 3800" essentially equivalent to two "64-1900" cores. Maybe I'm wrong - is the "3800" just an artificial performance number, perhaps measuring the average speed for a few typical situations? Are a fair number of these situations single-threaded? So X2 3800 really is much better than the 64 3400 in practice??

The ability to execute two threads is obviously useful. I guess I'm willing to tolerate a 20% drop in single-threaded performance in exchange for this ability. But a core going from 3400->1900 is too large of a drop.

Is there an unbiased source for benchmarks? AnandTech and Tom's Hardware Guide are chock full of ads and seem less informative than a few years ago. I'm not sure whether to trust them.

Edited by azagahl
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Another question...

Including the associated motherboard, is an AMD or Intel processor more likely to come with a DRM infestation? I haven't kept up much on (un)trusted computing, HDCP, etc...

Edited by azagahl
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>The reason why a Athlon X2 3800+ might be slower than a Athlon64 3800+ is because the 64-3800 is clocked higher. Each of the two cores in the X2 will be clocked slower, but AMD gives it the "3800" rating because the second core "makes up" for the lower clock speed.

When you write X2 3800 vs. 64 3400, I think from the point of view of a single thread and see 64 1900 vs. 64 3400. I'm assuming that an "X2 3800" essentially equivalent to two "64-1900" cores. Maybe I'm wrong - is the "3800" just an artificial performance number, perhaps measuring the average speed for a few typical situations? Are a fair number of these situations single-threaded? So X2 3800 really is much better than the 64 3400 in practice??

The ability to execute two threads is obviously useful. I guess I'm willing to tolerate a 20% drop in single-threaded performance in exchange for this ability. But a core going from 3400->1900 is too large of a drop.

Is there an unbiased source for benchmarks? AnandTech and Tom's Hardware Guide are chock full of ads and seem less informative than a few years ago. I'm not sure whether to trust them.

First off - the 3800+ number is artificial. That numbering scheme was deisgned by AMD to give a rough equivalent to the equivalent P4 system. So a A64 3400+ would be about the same as a P4 3.4GHz (with regards to single threaded applications).

And no - X2 3800 does not mean two 64-1900 cores (Like I already said above ;)). There are two cores both running at the same speed - 2.0GHz. This is MUCH faster than the old 1900+ systems (I've got an Athlon 2000+ at home, and even on single threaded apps, the X2 3800 will cream my system).

A single thread in the X2 3800+ system sees a 2.0GHz core. A single thread in the A64 3800+ sees a 2.4GHz. The rated clock speed is the speed at which a single thread will execute. You don't divide by two or four depending on the number of cores.

I could effectively make a dual core CPU by your reasoning, by having the processor "switch" between threads every other clock. That would sorta give you "two" cores, each at half the speed of the whole CPU (I know it's a bad example, but it proves my point). But, you wouldn't get any performance increase, like you do with a proper dual core CPU.

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>A single thread in the X2 3800+ system sees a 2.0GHz core. A single thread in the A64 3800+ sees a 2.4GHz. The rated clock speed is the speed at which a single thread will execute. You don't divide by two or four depending on the number of cores

I understand what you are saying in terms of clock speed. The single-core should be about (2.4-2)/2=20% faster for a single thread, i.e. the dual core is about 1-1/1.2 = 16% slower for a single thread. This slight performance loss is probably well worth it for having the dual-core advantage.

Unfortunately caches complicate things a bit. Are the L1 and L2 caches divided amongst the cores? What about memory bandwidth? Suppose that the core on the single-core CPU can hog all of the caches and memory bandwidth entirely to itself, whereas the dual-cores are burdened with half-sized caches and have to compete for memory bandwidth. Then the single-core has an even greater advantage than just its clock speed indicates.

BTW, I apologize if I'm asking about things that were figured out long ago.

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Unfortunately caches complicate things a bit. Are the L1 and L2 caches divided amongst the cores? What about memory bandwidth? Suppose that the core on the single-core CPU can hog all of the caches and memory bandwidth entirely to itself, whereas the dual-cores are burdened with half-sized caches and have to compete for memory bandwidth. Then the single-core has an even greater advantage than just its clock speed indicates.

BTW, I apologize if I'm asking about things that were figured out long ago.

No need to apologize. I figure that a lot of people have misunderstood the importance of dual core systems.

When it comes to cache separation, it depends on the CPU architecture. I can't tell you off the top of my head which does which, but there are various schemes for sharing the L2 and L3 caches between the two cores.

I think that in the end, all this discussion is more or less moot point, since people (and systems) are leaning more and more towards multiprocessing. Single core systems are really a thing of the past now, and almost all apps that you run nowadays use multiple threads.

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My friend argues that dual cores can help reduce stuttering, jerky frame rates in games. For example, when an e-mail arrives. It's hard to see how even a fast single-core can avoiding this.

I guess I'll get a dual-core, although I'm still a little bit skeptical.

Edited by azagahl
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please dont be skeptical, there is nothing wrong with dual core. especially since they are so cheap right now. they only reason i get jerkiness in games is if i do like 16xaa and 8xaf which is due to my vid card, my cpu could prolly run 2 games at once.

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zxian agrees with me :)

i think each core is limited to its own L2 cache..

Nope. Depends on the processor. Older generation Pentiums (like the 930) had individual L2 caches for each core (1MB OR 2MB) while newer Core 2 Duo have a single shared L2 cache (4MB typically). AMD X2s also have individual L2 caches for each core.

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like i said before

so what cpu are u going to get, amd or intel? an e6300 is about the same as my overclocked opteron 170 @2.6ghz. and the e6300 is ~183$ last time i checked

jcarle-ya i was thinking of amd, had absoultly no idea on the intel

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Just saw this thread, and I figured I'd pop in.

I work in an Internet Cafe, and we play -alot- of games here obviously. Most of our systems run AMD Athlon 3000+, 1G Corsair ValueSelect, and AGP nVidia 6800 GT's. We run pretty much any game we throw at them perfectly fine. Anything from WoW, to Counter-Strike/: Source, Battlefield 2/142, Oblivion.

Just because Dual Cores are out there, doesn't mean that they are right for you. In my personal rig I have a AMD Athlon 64 3700+, 1G Corsair ValueSelect, and an X1600XT Crossfire Ready (waiting on the money for the second card). And I hurdle through apps and games. I can do anything from Visual Studio, Adobe Premire/Photoshop/Imageready, to all the games I mentioned above.

My next Proc is probably going to be an Opty though. I'd like to OC and pop 3g+ on my CPU. I am going to need better Ram and probably a better PSU for that. I havn't had a chance to test my rails and see how stable my PSU is.

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well are you able to run all of those games at full settings? as far as apps go, any comp can really run them.

Yes you can, up to 1024*768 those games will run smooth, with a X850XT even 1280*1024/1440*900, but with NORMAL AA settings or none. I personally don’t use AA. All the systems here in this Internet Café are set on 1024*768 with no AA (some are still 15" TFTs).

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