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Need help understanding speeds of modern cpus vs. older ones...

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April 8, 2011 10:32:15 PM

Hi all,

I feel really odd asking this as I am pretty tech savvy (or I used to be) and I used to build my own systems all the time, but that was way back when Pentium 4s were the norm. Anyway, I seem to have missed the boat on the whole multi core cpu train. Probably because I run Ubuntu as my main OS and it runs just fine on pentium 4's...

I am really clueless when it comes to the clock speeds of newer cpus when compared with older ones.

For instance I have a P4 3.6ghz tower running my audio recording software.(i'm a musician) I get pretty good cpu usage levels with the Pentium 4, but I am going to be possibly be buying a laptop and am wondering what the performance will be like with say an I3 or an I5 or an I7 compared to the P4 3.6GHZ. I really have no idea.. I mean will an even an I3 beat a P4 3.6?

My other project is my home built arcade machine. I want to upgrade the PC inside which I think is a P4 3.2... I think most of the software running on that uses only single cores, so would a modern multi core cpu still be faster than a P4

I get the feeling I am really outdated using Pentium 4's so I guess almost anything would be an improvement, but you tell me...

When I look at newer processors and see clock speeds that are lower than the P4s I use, I have trouble making the comparison.
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April 8, 2011 10:46:11 PM

Here is a great article that explains differences quite well: http://www.tomshardware.com/reviews/best-gaming-cpu-cor...

Read the entire article for the full picture. Then pick the CPUs of your choice and read the specs on those CPUs.

The old P4s are single core. Newer CPUs are multi-core, and some are capable of being overclocked by enthusiasts.
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a b à CPUs
April 9, 2011 12:30:46 AM

Architectural changes have been made over time to improve core performance compared to older CPUs. A 3.6 P4 against even a single core of a Sandy Bridge i3@ 3.6 would probably take twice as long to do anything. The extra cores and hyperthreading will definitely improve the performance by over 4 fold at least; if you go with a 2500k and overclock it to 4.5ghz(with an aftermarket cooler) then you will see probably a 10 fold increase in speed. That is, of course, only if you can use the resources of the comp. The programs that use a single core will still see 2-3X the speed(theoretically speaking) with a 4.5ghz SB proc.
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a b à CPUs
April 9, 2011 12:33:29 AM

^That's a great article to show the best CPUs for the money, but it doesn't really give a comparison to the Pentium 4.

I'll try to give a short and sweet explanation. Firstly, the P4 uses a really, really old architecture and manufacturing process, meaning that clock-for-clock, it runs inefficiently and hot. The lack of multiple cores means that everything your computer throws at it will be shoved single-file through that one inefficient core. On a new quad core CPU, you have (theoretically) four times the processor power. Now, that isn't exactly true due to other limitations, but if a program is threaded (can use multiple cores), then the workload will be divided between each of the four cores - basically giving you four Pentium 4's in one CPU. The exception to this will be the Cache memory and other shared components, but they realistically won't make that much difference. Your clock rate will determine how fast each of those cores will compute information - a Pentium 4 may be clocked fast, but due to its outdated design and single core construction, it will be utterly destroyed by even a cheap dual-core processor clocked a good deal slower.

God, I should have broken up that into paragraphs. Sorry about that. :??: 
http://www.anandtech.com/bench/Product/92?vs=190
There's a good point of reference - a Pentium 4 660 against the Athlon II x2 265. The x2 265 is a fairly inexpensive dual core processor at $75, and you can see how utterly it destroys the old P4. You can change around the processors in the top and compare various other things if you like.

Onto your next question. Will you see improvement even if your software only uses one core? Yes. Because of the newer instruction sets used in modern CPUs and their more efficient design, the P4 will still crumble under nearly any modern processor. I hate to say that clock speed is becoming irrelevant, because it isn't - it's just that now, there are so many other factors that it's no longer the most important aspect. It still plays a huge role in poorly threaded applications, though - take AMD's Phenom II x6 for example - it has six cores, but for gaming, it's beaten relatively easy by a higher clocked x4, since your average game isn't very highly threaded and would rather have a higher clock speed than more cores.

I hope that helps explain things a little. I'll fix it up a little to actually make it readable once I post what I have so far... sorry about that...

:D 
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April 9, 2011 12:36:25 AM

While I didnt look at the article Ubrales posted the answer is simple... on air, at the die size of the p4, add to that processor noise (between the layers on the core) and they couldnt get much faster than 3.6ghz comfortably. So your basic answer is they are running about the same ghz but there are more cores (and shorter pipeline so it handles stuff much quicker). The software is what's really changed. its become multithreaded for the most part. That doesnt mean that the cpu itself is faster but because it can do two or 4 or 8 things at once it gets more done in the same amount of time.

Easy answer is buy the highest model number you can afford. the low end i7's are about equal to the high end i5's only the i7's have hyperthreading and the i5's dont.

The best way to think about it is ghz + number of cores + processor core model (for die size and functionality) = performance.
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April 9, 2011 2:00:30 AM

Wow, thank you so much guys, great responses and very detailed, this was definitely the info I've been looking for.

Basically I think I can safely say nearly any modern cpu will blow away my old Pentium 4s. Which is good news because even if I only upgrade to a slightly older dual core processor I should see an improvement...
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April 9, 2011 2:00:50 AM

Best answer selected by ShaolinD.
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a b à CPUs
April 9, 2011 2:09:14 AM

Not a problem. Glad to have been able to help. :D 
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