Hello, everyone! I’ve been doing some research into computer hardware lately, and one thing that I keep coming across is this idea that the speed of a processor, while important, isn’t the only thing that affects a computer’s overall performance. I’m having a bit of a hard time wrapping my head around this because I always thought that a faster processor meant a faster computer. Can anyone explain why this isn’t necessarily the case? I’m really interested to learn more about this!
In: 97
Hz means a processor can do **something** a number of times per second. GHz means it can do **something** billions of times per second which is amazing but we still don’t know what it’s accomplishing unless you look closer.
A typical operation might be “look up this number from memory and do some math with it” and you can imagine the speed of the memory is very important there. Also if you need to, for example, multiply 2 numbers together, an operation like that requires multiple steps to move the data to the correct part of the CPU and actually do the multiplication operation, which uses more than 1 cycle (Hz) to accomplish. Some CPUs may do it more efficiently than others. If you can finish multiplication in only 4 steps instead of 5 steps but your multiplier design takes up more space on your chip and limits the attention you can pay to other parts of your design like the speed that you can do addition… what do you prioritize?
Modern processors also use tricks to guess what they’re going to do next so they can get a head start on it. This can be extremely useful but also complicated, works differently depending on the exact task, and of course if it is done wrong it’s a lot of wasted effort. The Pentium 4 processor is an infamous example of a processor that did this differently from other designs and did a very bad job *in certain tasks* because its predictive execution (guessing the next step) was frequently wrong.
The processor often has to wait for other devices to do things before it can complete tasks. For example, it might have to retrieve information from (or write information to) a hard disk, a network connection, or the RAM – it might even have to store information in the RAM temporarily during its calculations, since the amount of data the processor can store internally is quite small. Many computers have a graphics card (aka GPU), which is essentially a separate CPU that is specialized for processing graphics. If so, the CPU essentially delegates various types of processing to the graphics card. There may be some other specialized devices that the CPU defers to sometimes too, such as a sound card or security devices.
The motherboard manages the flow of information between many of these devices, so it can also have an impact (though in many cases, motherboards are simply incompatible with newer components instead of being too slow for them).
Nowadays, CPUs are very complicated and the quoted speed (3 GHz or whatever) doesn’t tell you everything about their performance. They have different numbers of cores and different cache sizes, and they are often designed to step their speed up and down, maintaining the maximum speed only for short bursts. The computer’s ability to cool itself (depending on fans, air holes, how cluttered/dusty the inside is, the external temperature, etc.) can have a big impact on this.
The processor is one of the most important parts of a computer, but there are a number of other components that also make up a complete computer. Depending upon what you are trying to do, the speed of these other components can also be important to a computer’s overall performance.
If the program you are using loads or handles a lot of data, or needs to constantly load and write data, the performance of the drive(s) that the data is loaded from or written to is very important. If your program is very graphics-oriented (such as a game,) a faster video card may be a bigger boost. If the program requires a lot of memory to operate (to keep large amounts of data in memory while manipulating it, etc.) more RAM may be needed.
It is not unusual for your CPU to be idle a lot of the time while it is waiting for other components to complete their task. A faster CPU will not help if the bottleneck is that the computer is loading data from a low-speed platter drive or if it does not have enough memory to keep everything in the main memory while running a very large program.
Your computer crunches a lot of data. Picture data like a highway, or road system. Sure, you may have a 6-lane highway but if it turns off into a 2 lane back road, traffic’s gonna back up.
Think of your processor like the engine in your car. Turn the engine faster and the car moves faster – simple, right?
But what engine is it? What are the gear ratios? You could probably make a lawnmower engine move a car if you gear it low enough and the engine will certainly be spinning really fast, probably faster than a V8 in the same car but the V8 will certainly be faster than the lawnmower engine.
Even if you have the best car with the best engine, you can still get stuck in traffic and slowed to a crawl
For your computer, the processor is one of the critical parts of the computer but it can only do so much on its own. It needs memory to store information and the memory can only read and write so quickly. It also needs to access information from long term storage or other computers which takes time and it may have a separate specialist processor like a GPU for some tasks. All these separate parts are joined together by other components called buses and they can only communicate so fast.
Even if you make the processor (CPU), GPU and RAM as fast as possible and load everything into RAM to eliminate network and disk access, the GPU, RAM and CPU can only work together as quickly as the bus allows. Putting the best parts on the cheapest motherboard that will hold them is like having a massive city with no major roads between residential, commercial and industrial areas and constant traffic problems – it no-longer matters what each part can do alone because they can’t share information fast enough so they keep waiting for the message to get through from the other parts
This is what generally is referred to as Bottlenecking.
A bottleneck is where a particular step in the process holds up the entire process. A computer is lots of components talking to each other, and if those other components can’t keep up you’re going to have a processor that is spending a lot of time waiting for instructions.
Other components that can slow down a processor are:
a. RAM, Random Access Memory. RAM needs to be able to keep up with the processor to some extent. Both in terms of “how many cycles per second can your RAM do” and latency (how many cycles does it take to get a response). While processors do have some internal memory (the L1 and L2 cache) to speed up processing those caches are very limited (like, 512k per core normally. Or even less).
b. Bus speed. The Bus is kind of the highway of the computer. Everything travelling from one component to another goes over the bus. Motherboards tend to be designed with a certain level of components in mind.
c. If you need to retrieve lots of different data, then how fast memory is retrieved from the harddrive matters.
d. Processors are generalist machines. You can connect specialist devices to them that are much better at particular tasks, like a GPU. GPUs are especially good at handling calculations related to graphic (hence the name) but some other tasks as well (so for example machines mining crypto will tend to use high end GPUs because those have more cores that does the stuff they need).
The cpu is like your brain, very important. But how useful is it if you had no legs and couldn’t walk, arms to grab, mouth to speak, etc.
So the cpu needs to work together with other parts depending on your goal. If you want to jog a marathon you would need strong legs. If you want to play video games you’ll need a good gpu.
So depending on what you want the pc to do, other parts are factored in.
Your CPU often has to wait for data to process. RAM is slower than the CPU, and your hard drive / SSD is slower still.
Faster RAM and faster drive = less time the CPU is waiting for data.
Also more RAM = less need to keep fetching data from your drive = less waiting time.
Also you have the CPU heatsink, modern CPUs detect of they are getting too hot and slow down. Better heatsink = cooler CPU = no slowing down.
Then there’s the graphics card. These are much faster than the CPU at drawing 3D graphics so better graphics card = more FPS in games (also some things more video rendering can use the GPU).
Think about Stephen Hawking. Great brain but tetraplegic.
So he needed assistance to do everything outside thinking.
Imagine his nurse being an asshole and making him wait forever to get a sip of water that he needs so he can continue his thinking work because dehydration hinders his thinking abilities.
He looses two hours of thinking because the nurse is poorly trained or an asshole.
Now imagine the same scene but with a nurse that is committed to his work and is constantly doin back and forth to please Stephen needs to carry out his mental work.
That’s about it.
CPUs are useful but must be fed fast enough for their potential to be unleashed.
If you pair a fast CPU with slow RAM there is only so much data that the CPU can crunch at every given time. This is called a bottleneck
If you pair that same cpu with blazing fast RAM, the CPU could churn away constantly without spending so much time waiting for data.
So basically, it’s handicapped. Will processors ever be an all in one device?
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