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Megahertz Myth

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July 15, 2009 11:46:53 PM

I first learned when I first got my 2.2GHz San Diego 3700+ mid 05' that AMD used lower clock rates than Intel. I think that at the time, the 2.2GHz processor I bought was comparable to a P4 @ 3.0GHz or so. I was wondering how the i7 920 at stock 2.66GHz compares to the stock Phenom's at the same frequency. I can get a stable OC on my 920 at 4.0GHz, how does that compare to the OC you can get on the Phenom's and their frequency? Is there much of a difference nowadays than there was in the past?

More about : megahertz myth

July 16, 2009 12:10:17 AM

Compared in what? Gaming? Video rendering/encoding? ...etc.
It depends on what you want to achieve.

For something like x264 encoding which is what i7 is really good at, assuming HT is turned on with 8threads, it takes around 3.7-4Ghz for a Phenom II X4 (they top out ~4Ghz on air) to match a i7 920 @2.66Ghz from data I've seen.

If it's gaming at high res. with max. eye candy, any Core2/Phenom class processor over 3.2Ghz makes no difference. It's all down to the graphics card from then on.
July 16, 2009 12:15:03 AM

Thx for the reply. I was thinking compared to the whole package, meaning a litany of stress test in gaming, video encoding, etc.
Related resources
July 16, 2009 12:29:22 AM

To answer you exact question, AMD is still way behind clock for clock, and they still don't overclock nearly as well as the intel. Don't get me wrong, I like AMD for budget builds, so AMD fans please don't flame me. Toms just ran an article comparing the i7 920 to AMD's fastest chip, the 955. At stock speed the i7 still blew away the much faster clocked AMD in almost everything. And in gaming, even though the AMD system had crossfire 4890s and the i7 had 4870s, they had about the same scores....if both systems had the same video cards the i7 would have won by a wide margin there also. Bottom line is you can't compare clock speeds between AMD and intel, they are very different.
July 16, 2009 12:36:24 AM

belial2k said:
To answer you exact question, AMD is still way behind clock for clock, and they still don't overclock nearly as well as the intel. Don't get me wrong, I like AMD for budget builds, so AMD fans please don't flame me. Toms just ran an article comparing the i7 920 to AMD's fastest chip, the 955. At stock speed the i7 still blew away the much faster clocked AMD in almost everything. And in gaming, even though the AMD system had crossfire 4890s and the i7 had 4870s, they had about the same scores....if both systems had the same video cards the i7 would have won by a wide margin there also. Bottom line is you can't compare clock speeds between AMD and intel, they are very different.


So Intel is faster, or "better" at everything, but is it really worth paying 2, 3, or 4 times the price? for a difference that is impossible to notice without some benchmarking program?
and I'm guessing intel scored better because Intels cpus are "quad-pumped" opposed to amds cpus only being "double-pumped"
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July 16, 2009 1:58:49 AM

JDV28 said:
So Intel is faster, or "better" at everything, but is it really worth paying 2, 3, or 4 times the price? for a difference that is impossible to notice without some benchmarking program?
and I'm guessing intel scored better because Intels cpus are "quad-pumped" opposed to amds cpus only being "double-pumped"


No, Intel doesn't use a QDR FSB any longer, and AMD no longer uses a DDR FSB. They both use on-die memory controllers to eliminate that bottleneck, so Intel has around 2.5x the bandwidth of AMD. A year ago, when Intel was using FSB but AMD had already switched, AMD had around 2x the bandwidth of Intel.
July 16, 2009 2:03:49 AM

Huh, alright, Thank you. Apparently my knowledge was outdated. So your post confused me, what is it currently?
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July 16, 2009 2:11:38 AM

JDV28 said:
Huh, alright, Thank you. Apparently my knowledge was outdated. So your post confused me, what is it currently?


It's nothing, there is no FSB. AMD has an internal link that runs at 2000 million (2 billion) transfers per second (2 GT/s) in each direction simultaneously (labeled "4000 MHz" which is actually 4 GT/s), and Intel has something similar at 2.4 GT/s (labeled 4.8 GT/s)
July 16, 2009 2:37:22 AM

Ok, so currently, Intel is a tiny bit faster?
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July 16, 2009 2:41:51 AM

Crashman said:
It's nothing, there is no FSB. AMD has an internal link that runs at 2000 million (2 billion) transfers per second (2 GT/s) in each direction simultaneously (labeled "4000 MHz" which is actually 4 GT/s), and Intel has something similar at 2.4 GT/s (labeled 4.8 GT/s)


JDV28 said:
Ok, so currently, Intel is a tiny bit faster?


Yes
July 16, 2009 2:52:52 AM

But really, logically, its not worth paying about 2 or 3 times the price?
(i realize that its almost all personal oppinion on that)
July 16, 2009 3:08:03 AM

That is well outside the OP question. I was just trying to answer his question, not promote intel over AMD. If I were going to start a new budget build I would seriously consider an Phenom II x2 or x3. But at the high end an intel will cost only slightly more (about $100) and give a 25% + increase in performance and be more viable for a longer period (more advanced platform). So actually in the high end market, intel has a better price to performance ratio.
July 16, 2009 3:10:36 AM

We were just discussing the differences between amd and intel. And thanks.
July 16, 2009 3:15:14 AM

Thx for all the replies. I'm not asking about any price vs. Performance aspects, simply put, when you read its given frequency on the processors box, how does it compare to the other brands frequency for a comparable processor? Is a comparable AMD quad core at 2.2GHZ the same as an intel quad core at 3.2GHz? I think I've gotten some good answers though that suggest they are still not a 1:1 ratio.
July 16, 2009 3:27:58 AM

It is hard to give an exact answer, because it will depend on the app, but in general an i7 is 25%+ faster than a similar clock on an AMD. So, a i7 920 at 2.7 is roughly the same as a an AMD at 3.3. BUT, some apps will exaggerate the difference and make it more like 75% faster, and some will minimize the difference.
July 16, 2009 3:52:21 AM

its all about your needs... apps/game your using.
July 16, 2009 4:03:42 AM

boulard83 said:
its all about your needs... apps/game your using.



So you're saying that the ratio of AMD clock frequencies vs Intel clock frequencies changes depending on what benchmark is used? I'm looking for an overall general easy to remember equation that probably isn't totally accurate but close (i.e. AMD clock frequencies times 1.5 equals Intel's clock frequencies.)
July 16, 2009 4:06:11 AM

One thing to look for, and this is very pertinent to the OPs question, is said i7 at 2.66 is using turbo. One needs to find that out in any benchmark done using i7, as itll run the clocks up to almost 3Ghz using turbo, so the %'s change alot.
July 16, 2009 4:08:40 AM

JAYDEEJOHN said:
One thing to look for, and this is very pertinent to the OPs question, is said i7 at 2.66 is using turbo. One needs to find that out in any benchmark done using i7, as itll run the clocks up to almost 3Ghz using turbo, so the %'s change alot.



Good point, and I'm sure that my equation that I am looking for is probably not linear either :/ 
July 16, 2009 4:18:08 AM

You guys are all just fuding.
July 16, 2009 4:20:21 AM

uhmmmm.....am i invisible? I'll try again. 25%+ is a good base to look at (not counting turbo). So your formula would be i7 is 1.25 faster than phenom II....but understand that will vary greatly (probably +75% /- 10%) depending on the app.
July 16, 2009 4:23:52 AM

If the OP is going to use benchmarks, then what I said was specific, and is why I pointed it out
July 16, 2009 4:24:36 AM

belial2k said:
uhmmmm.....am i invisible? I'll try again. 25%+ is a good base to look at (not counting turbo). So your formula would be i7 is 1.25 faster than phenom II....but understand that will vary greatly (probably +75% /- 10%) depending on the app.


Belial, I did get what you said, I was simply responding to boulard because I wasn't sure he understood what I was asking. Thanks for your input.
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July 16, 2009 5:04:06 AM

I know the OP is asking about Core i7 : Phenom II...
But how about Phenom II : Core 2 Quad? Is it almost 1:1?
I think I've read something like Phenom II 3.0 GHz: roughly the same as Core 2 Quad 2.8 GHz; but I may be wrong here.
July 16, 2009 5:09:11 AM

Those test also show the stock speed numbers. Keep in mind the point of that article was VALUE not performance... That is why the i7 was handicapped with slower graphics cards and a slower clock speed (it could have been overclocked much higher). The test was to see if you spent the same amount of cash on each system how they would perform. Sort of an AMD vs i7 SBM. But it is good to show the difference the OP is interested in. Of couse, if both systems had the same cards and exact same clock it would show the i7 difference we've talked about.
July 16, 2009 5:11:36 AM

Intel still wins with the c2q, but not by as much. c2q also lose to the i7 clock for clock.
July 16, 2009 5:47:23 AM

t33lo said:
So you're saying that the ratio of AMD clock frequencies vs Intel clock frequencies changes depending on what benchmark is used? I'm looking for an overall general easy to remember equation that probably isn't totally accurate but close (i.e. AMD clock frequencies times 1.5 equals Intel's clock frequencies.)


Ill just tel it again. ITS allll about your needs apps/game/encoding/whatever you do.

If your an hardcore encoder, look for the CPU that'll give you the best of it. if your a gamer ? ... you know what ill say ....

Im personnally mostly a gamer. So i need a fast CPU + good GPU and RAM. My 3.74ghz quad is enough to feed my GTX285 and temps are awesome. i know i can go higher, ive done it .... but i dont need it. i prefer to keep it nice and cool with better lifespan.

Currently the P2 X4 are really nice. but ths I7 is still better ... nearly all the review put the I7 ahead and if you speak about clock for clock the I7 is just alwais leading. P2 X4 are meant to be compared to C2Q 9xxx and 8xxx. but again ill prefer the intel .... ive build AMD computer recently and SRY but my hearth is to INTEL atm ...

SO ! dont just ask a question to start a big debate like its happening in there ... look at your needs and now youll know what youll have to buy as CPU ...

have fun !
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July 16, 2009 6:42:47 AM

t33lo said:
Thx for all the replies. I'm not asking about any price vs. Performance aspects, simply put, when you read its given frequency on the processors box, how does it compare to the other brands frequency for a comparable processor? Is a comparable AMD quad core at 2.2GHZ the same as an intel quad core at 3.2GHz? I think I've gotten some good answers though that suggest they are still not a 1:1 ratio.



I'll make this easy for you:

1.) That thing about AMD processors having more performance per clock? It went away when Intel switched from P4 architecture back to enhanced P3 architecture. Back then it wasn't that AMD's were so good, it was that P4's were so bad.

2.) Core 2 Duos perform a little bit better than Phenom II Dual Cores overall, clock-per-clock. But since they don't outperform the Phenom II at everything, it's hard to quantify.

3.) Core 2 Quads outperform Phenom II X4's by a little bit on average, but again because they don't win at everything its hard to quantify

4.) Core i7's outperform Core 2 Quads in some things, but not in others. They're about 2 performance factors ahead of AMD, since the Core 2 Quad is one performance factor ahead of AMD. But once again, it's hard to quantify.

5.) Intel's current architectures overclock a little bit higher than AMD's current architecture, so you can get both better clock-for-clock and higher clocks with Intel.

6.) Because of all those little "in-general" and "on average" leads Intel has, AMD is practically giving away it's chips. You often get a better value with AMD.
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July 16, 2009 7:02:28 AM

boulard83 said:
Ill just tel it again. ITS allll about your needs apps/game/encoding/whatever you do.


And budget.
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July 16, 2009 11:57:25 AM

I'll explain the whole Megahertz myth:

The easiest way to put it, is when it comes to speed of execution, there are three factors:
1: How often the component can LOAD/SEND data (Ghz)
2: How much data can be transferred/stored at one time (Bus Width)
3: How much data can be executed per clock cycle (Instructions Per Cycle)

The Pentium4, for instance, went with a high GHz speed in an attempt to overcome a low Bus Width and low ICP. The Athlons went for a lower Ghz speed, and higher ICP in response.

The Core2 line, on the other hand, has a much higher ICP, and eventually reached P4 levels when it came to GHz. Even on one CPU, a duo would beat a P4 due to its higher ICP.

GPU's, on the other hand, went with a far lower GHz speed, but has a much larger data bus (256/512 instead of 32/64) to achieve simmilar speed of execution.

In terms of current performance, I'd argue that late C2Q's have a slightly lower ICP then i7's, although I'd be interested to see head to head comparisions between a i7 920 (2.6GHz) with Hypterthreading off and a Q9400 (also at 2.66 GHz). Keep in mind, the diffrences in cache size/structure, and tri-channel RAM can also effect the results. In apps that don't take advantage of i7's hypterthreading, it appears that late C2Q's are even with i7 most of the time.

Phonom II's (on AM2+ platform) match against later C2Q's (8000-9000 series). Based on subjective analysis, I'd say Phenom II's have a lower ICP then C2Q's, but its hard to quantify, as some apps clearly favor one platform over the other. The difference is neglegable in any case, as a 2.66Ghz Phemon II is a good match against a 2.66 C2Q.
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July 16, 2009 5:49:18 PM

gamerk316 said:
...I'd be interested to see head to head comparisions between a i7 920 (2.6GHz) with Hypterthreading off and a Q9400 (also at 2.66 GHz). In apps that don't take advantage of i7's hypterthreading, it appears that late C2Q's are even with i7 most of the time.
IMHO you might as well claim that a 2-core processor is just as good because most applications aren't able to run 4 threads at once. Hyperthreading wrings actual productive work done out of otherwise-unused pipeline cycles, and it's a very real advantage.
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July 16, 2009 6:57:28 PM

Yes, hyperthreading leads to better performance, but you can't compare 8 to 4. I want to see how a i7 at 2.66GHz running up to 4 threads competes against a 2.6GHz C2Q running up to four threads. This is the only way to compare ICP between the two processors, and thats to use the same exact specs.

(One stick of 4GB of RAM at 1066Mhz would be used, to eliminate dual/tri channel and memory speeds from the comparison as much as possible)
July 16, 2009 7:27:21 PM

But a primary factor of IPC is whether or not the CPU has data to work on every cycle. Things like cache, HT, and faster memory access (IMC) allow the CPU to use more of its cycles. In this way, HT increases IPC.
July 16, 2009 8:17:53 PM

Ive seen lots of PPL disabling HT and have better performance while gaming but encoding and lots of apps are faster if HT is enabled. Remember this is NOT 8 core, but 8 thread.
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July 16, 2009 8:29:36 PM

Dekasav said:
But a primary factor of IPC is whether or not the CPU has data to work on every cycle. Things like cache, HT, and faster memory access (IMC) allow the CPU to use more of its cycles. In this way, HT increases IPC.

Exactly. Turning off hyperthreading in order to get a more "pure" performance number is akin to disabling the caches to see what the "real" memory bandwidth is. Sure, you can get a statistic from it - but in real life why the heck would you want to do it?
July 16, 2009 11:12:22 PM

Quote:
I'm looking for an overall general easy to remember equation that probably isn't totally accurate but close

The example I gave is my first post is about as extreme in difference as it gets.
Core i7 9xx simply doesn't make sense for gamers while pure performance, performance/$ and performance/watt in the area of massively multithreaded environment blow the competitors away.

While generalisation is an easy thing to remember, one must understand this is the worst way to go when making purchasing decisions.
This applies to all other things in life.
July 17, 2009 12:06:15 AM

^^ I generally agree
July 17, 2009 12:07:06 AM

JAYDEEJOHN said:
^^ I generally agree

*bastage* :lol: 
July 17, 2009 12:16:37 AM

heheh
But I do, I really do.

Knowing your needs is paramount, as well as your wallet.
July 17, 2009 12:22:04 AM

Looking at this link
http://www.wepc.com/discussions/view/6612/Two_Important...
which addresses much of this, the one place I disagree with on Anand is his speaking to the ease in which to make those decisions, where if anything , I think Intels greatly muddied the waters, be it by pricing, new skt or upgrade path
July 17, 2009 10:20:35 PM

great discussion everyone, definitely learned some things. I for one got the i7 because of the reviews and I generally upgrade every 4-5 years so hopefully by then apps will utilize all 4 cores better. Just was curious on the whole debate that was probably more alive back during the P4 era.
July 17, 2009 11:17:00 PM

gamerk316 said:
GPU's, on the other hand, went with a far lower GHz speed, but has a much larger data bus (256/512 instead of 32/64) to achieve simmilar speed of execution.


It's not the bus that makes the difference (though GPUs do have a huge appetite for memory bandwidth), it's the huge number of 'cores' inside the GPU. If you're filling a 100-pixel triangle you can use 100 'cores' to process the rendering for each pixel individually and get it all done 100x faster than if the GPU only processed one pixel at a time.

CPUs tend to be mostly cache with a few processing cores, whereas GPUs tend to be mostly processing cores with a bit of cache (though recent CPUs with integrated memory controllers require less cache for optimum performance and hence are heading in the GPU direction).
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July 17, 2009 11:52:13 PM

True, and besides, the i7 with its tri channel memory actually has a 192 bit bus, which is closing in on the size that many GPUs have. The main difference is in core count and complexity.
July 18, 2009 3:49:32 AM

Complexity is the current issue, as cpus complexity actually gets in the way.
LRB will be emulating alot of what it does, simply because of this. Having all the extras of a cpu,LRB and its makers/designers, are actually trying to keep them as positives, having all that cache etc, tho, the core count and the latency (core clocks can be made up to account for this) can be solved, its just the drivers that needs work.
Id point out tho, starting with the 200 series, gpus are also heading in the crossover area, having more cache etc, plus adding more cores, and using DP, which is mainly for gpgpu functionality
July 18, 2009 6:07:32 AM

wuzy said:
Compared in what? Gaming? Video rendering/encoding? ...etc.
It depends on what you want to achieve.

For something like x264 encoding which is what i7 is really good at, assuming HT is turned on with 8threads, it takes around 3.7-4Ghz for a Phenom II X4 (they top out ~4Ghz on air) to match a i7 920 @2.66Ghz from data I've seen.

If it's gaming at high res. with max. eye candy, any Core2/Phenom class processor over 3.2Ghz makes no difference. It's all down to the graphics card from then on.


I disagree, here is a very good review which shows that i7 920 is not equal to the P2 955BE at high resolutions with 2 or more GPUs. With one GPU, the difference is small, but with 2, the difference can be quite large. The review shows a Q9770 @ 3.2GHz, which is faster than a P2 955BE, still cannot keep up to an i7 @ 3.2Ghz.

http://www.guru3d.com/article/core-i7-multigpu-sli-cros...

July 18, 2009 6:20:31 AM

"Core i7 platform is a fantastic platform for multi-GPU gaming as you'll gain heaps... seriously heaps and heaps more performance opposed to today's regular PCs with a Core 2 Duo processor".....but these guys arguing for their dual cores won't let facts get in their way. They are convinced dual core processors are all they will ever need, while those of us who have stepped up to quad cores know the truth.
So just one more time and then I'll give up. Quad cores will outperform dual cores clock for clock, or even slightly slower clocked, in EVERYTHING including gaming. So there really should be no question about performance. If you want to argue which system you can build cheaper feel free to have at it. But please stop spreading the misinformation that dual cores are "better" at gaming than quad cores.
July 18, 2009 6:49:12 AM

belial2k said:
"Core i7 platform is a fantastic platform for multi-GPU gaming as you'll gain heaps... seriously heaps and heaps more performance opposed to today's regular PCs with a Core 2 Duo processor".....but these guys arguing for their dual cores won't let facts get in their way. They are convinced dual core processors are all they will ever need, while those of us who have stepped up to quad cores know the truth.
So just one more time and then I'll give up. Quad cores will outperform dual cores clock for clock, or even slightly slower clocked, in EVERYTHING including gaming. So there really should be no question about performance. If you want to argue which system you can build cheaper feel free to have at it. But please stop spreading the misinformation that dual cores are "better" at gaming than quad cores.


Unless the game is coded for 2 threads and you have a single GPU. :) 
July 18, 2009 7:18:01 AM

A good gamer has his system optimized for gaming, that means as little as possible going on. Most games dont benefit from quad core. Dual cores clock higher than quads.


^^^ All the above is true and factual. People have to make up their own minds
July 18, 2009 12:37:30 PM

one-shot said:
I disagree, here is a very good review which shows that i7 920 is not equal to the P2 955BE at high resolutions with 2 or more GPUs. With one GPU, the difference is small, but with 2, the difference can be quite large. The review shows a Q9770 @ 3.2GHz, which is faster than a P2 955BE, still cannot keep up to an i7 @ 3.2Ghz.

http://www.guru3d.com/article/core-i7-multigpu-sli-cros...


Yes indeed, the exception goes to 2 GPUs or more setup where the X58 platform holds an advantage. But the difference @2650x1600 is not night and day, just enough difference when benchmarked.

*reminds self not to generalise next time*
!