What is the relevance of 'Ghz' when comparing processor speeds?

Question

I'm so confused right now.

I'm upgrading my computer and am debating weather to invest in a new, faster processor to support my Radeon HD4870 I'm going to buy.

My current processor (which I've had for at least 10 years) is a Pentium 4 running at 2.80Ghz.

Now, I keep being told that I need to upgrade it if I want to play all the new games so I'm currently browsing through various sites looking for a new one.

Now I'm told I need something that is 'quad core', so I go to amazon, search for quad core processors and I'm given a list of all these processors which say they are quad core.

Now here's where I get confused...

As I previously mentioned, my 10+ year old processor (according to my 'view system information' window ) is running at 2.80Ghz and yet, according to amazon, some of these 'quad core' processors (which cost about £100!) say they're running at 2.30Ghz, 2.60Ghz or 2.80Ghz (the same as my current one).

What gives?

Does a 'quad core' processor mean that it has 4 CPUs each running at 2.30Ghz, 2.60Ghz or 2.80Ghz...

...meaning that a quad core 2.80Ghz processor is actually running at...

2.80Ghz x 4 = 11.20Ghz?

Thanks to anyone who can clear this up for me, really appreciate it.

Answer 1

No, you can't add the speed of the cores.



A quad core is 4 cores running at the rated speed of 2.8 Ghz or whatever, NOT 2.80Ghz x 4 = 11.20Ghz.



The key is that they are running simultaneously, doing 4x the amount of processing (not processing speed) of a single core processor. BUT, that only works if the application you are running can take advantage of all the cores, and many apps can't (or don't need to).



Other improvements in memory, graphics and hard disks will make a newer computer faster as well, so it may appear like 2.6 Ghz is faster that 2.8 Ghz when it is a quad core. Note also that speed benchmarks for a given mult-core chip assume all cores operational, which in fact may not be the case.



So, if you have a game that can only take advantage of a single core (and a lot of games are like that), running it on a quad core will give you no advantage. Using Photoshop on the other hand will decrease the processing time substantially, but even in this case one core will do more work than the others; it actually sends threads out to the other cores for processing.



If you are upgrading to play games be sure the game can utilize the extra cores, if not, you are not going to get the improvement you expect. Go here for a comparison of current processors and the games benchmarks: http://www.tomshardware.com/charts/2009-desktop-cpu-charts/benchmarks,60.html

Answer 2

A dual or quad core is like having 2 or 4 seperate CPUs. This means, in theory that the processing load or work is shared between 2/4 CPUs. Presumably they both have speeds of 2.8 effectively making 5.6

I am not sure but I believe there is more to this than meets the eye. Like most things there is an element of sales hype in this.

The speed of a CPU is the speed it cycles through its instruction set. This is why a Mac has slower CPU clock speeds but runs faster (because it uses RISC (Reduced Instruction Set Computer). Next you need the motherboard to keep up! Usually the M/B runs at half the speed of the CPU and therefore misses out every other clock cycle. Then Memory plays its part, and Hard drives and controllers etc. etc. The eventual speed or performance will be reliant on the weekest (slowest) link.

Answer 3

Mhz is the frequency in which your computer carries out instructions.



Think of it like a librarian, fetching books from the shelves and bringing them to the front counter.



She could walk 100 times per hour for a distance of 50 metres, OR she could walk 25 times per hour for a distance of 10 metres. Even though the second scenario is at 1/4 the speed, because the instruction is so much easier to execute it works out to be faster. Mhz can be the same way.



In this way, frequency doesn't mean much. It depends on how the core was designed, the architecture, ability to execute floating point instructions, L1/L2 Cache available, FSB speed.....



Also a really big factor is whether or not the memory controller is resident on the chip itself or controlled out of the North Bridge. Traditionally this gave AMD a big advantage as they were the first to put it on board, and one of the same factors that makes the I7 an unbelievable chip.



Also, many apps are not written to take advantage of Quad Core, so even though you have all that power available, it will only run on one or two cores.



There are a lot of factors, I personally prefer dual core for expense VS usable performance, and I think most gamers would agree. Most heavy quad core users are things like graphic design and such.

Answer 4

The GHz is the speed of each core. If you have quad core, thats 4 processors running at that speed. It is processing the amout of data a 11.2GHz single processor would do, but it doesnt have to go as fast.

Answer 5

GHz is relatively useless unless you are comparing processors from the same direct line. Look into FLOPS, Floating Point Operations Per Second. That is a true measure of processors.



To explain it simply, it's like RPMs in a car... it has no real correlation to how fast or powerful the car is, just how fast the engine is turning.



There are numerous benchmarks avaialble that compare processors. Just google for them.

Answer 6

2 GHz is nice, even the 64x2 5800 is in basic terms around 2.8 GHz. Ram is actual a extra robust element in perceptible velocity. i could recommend at a minimum a million GB or much extra effective could be 2 GB in twin channel mode.

Answer 7

the data analysis and programs are run differently among the 4 cores. basically by dividing up the work amongst the components, more will be done faster.



Ghz is like your comptuers horse power. something around 2 is not very good, 3-3.5 is best i would say. but quad or dual cores above 2.3 are good as well.



just make sure you get a lot of memory/RAM.... atleast 4gb if you want ot have a good stable system to hedge all possible malfuntions with speed as well as processing power with programs and applications.

best of luck.