cache - Curios: What makes CPUs better than others?
2014-07
Zizma
I have been wondering about this for a long while now and was hoping someone here could answer it pretty easily. If I was looking for the most powerful CPU what should I really be looking at? There are so many different parameters of a CPU and I am wanting to know what each thing does and what really matters. Basically this: What is the deal with cores? If I take using optimized applications out of the mix would it theoretically better to get quad core 1.0GHz CPU or a 1 core 4 GHz CPU? Also, what is the difference between maybe an Sandy Bridge CPU versus an Ivy Bridge CPU? If they both were had the same clock speed and number of cores would the Ivy Bridge perform better? Does an older Xeon with an equal clock speed and number of cores to a new i7 really perform worse/slower? Does size matter? Why would I go with a 22nm CPU over a 32nm when the size difference is so trivial? What about the cache? When does the cache come into play with performance?
Alok
Without a good understanding of underlying CPU technologies and the applications that use them, it is unfortunately non-trivial to compare two processors from different lines or determine a 'most powerful' CPU.
Why would I go with a 22nm CPU over a 32nm when the size difference is so trivial?
It is hardly trivial in percentage terms; as that is a 1/3rd reduction. The smaller size means that:
- more complex circuitry can fit on the same die size
- less heat generation, which allows usage of smaller heat sinks or more overclocking
- the 22nm one is likely newer, and has other architectural improvements integrated as well
What is the deal with cores? If I take using optimized applications out of the mix would it theoretically better to get quad core 1.0GHz CPU or a 1 core 4 GHz CPU?
Multiple cores allows the system to run more than 1 application without having to context switch, it can also help with overall responsiveness as your foreground application doesn't starve the OS of CPU resources.
Most typical computer applications don't max out each core, so more of them will improve performance. Conversely, in some cases like games which make heavy use of a single core but aren't optimized for multiple cores, the performance is better with higher clock speed per core.
If they both were had the same clock speed and number of cores [... which does better?]
As a rule of thumb, the newer one should do better as it has the latest architectural improvements (better pipeline prediction, lower branching penalty etc.) integrated.
erikric
Back in the days clock frequency used to be THE criteria to compare CPUs (or perhaps you had to take into account whether it was a DX or SX). The world was simple back then, but in these fast evolving modern times, it's not so easy to figure out to best spend your hard earned cash on a new CPU.
Could someone please enlighten me as to what kind of applications benefit from different aspects?
When should you choose more cores over clock speed? What is cache and when do you need it the most? Gaming? Video editing? Development?
- Clock frequency:
- Number of cores:
- Cache memory:
- Other:
Sirex
more cores: good for doing multiple jobs (hosting virtual machines, etc) more speed: good for doing each job faster
cache is basically a much much faster (and smaller) RAM memory that lives on the cpu. The amount you need depends on the workload, and how often the cpu is swapping data in and out, but more is better. It normally "stepped" as the faster cache is more expensive and hence smaller, so you get level 1, 2 and 3 cache, 1 being the fastest, youll normally find a certain amount of each on a cpu. The cpu will try to keep data it needs the most often in the fastest cache it has space for it.
Its a pretty wide ranging question you've asked though, prolly easier to point you to google and search for the proper articles on the subject.