how important is l1/l2 cache in shopping for cpu?

[Skylais]

question in the title. Thanks guys

 

[kbrady1979]

Most modern CPU's will have about the same L1/L2.....and will have a different amount of L3 cache. Give me an example of CPU's that you are comparing

 

[LMiller7]

Level 1 and level 2 caches are very important to performance. All modern processors have them. But there are numerous other important factors as well. If you could clarify the question a better answer can be provided.

 

[Skylais]

Level 1 and level 2 caches are very important to performance. All modern processors have them. But there are numerous other important factors as well. If you could clarify the question a better answer can be provided.

okay well let's see. Say we have a dual core 3.3 ghz processor with 1mb l2 cache and then like a 3.0ghz proc single cored with 8mb l2 cache. ? What does the cache really do? and how much of a performance boost does it give?

 

[LMiller7]

Dating back to the 1980's system memory has been much slower than the CPU. Providing an adequate amount of system memory that matched the CPU in performance would be prohibitively expensive. Normally this would very seriously impact performance. To solve this problem all modern CPUs include a Level 1 and Level 2 cache. The level 1 cache contains the most recently accessed data. If the CPU requests data that is in the cache the access is very fast. The problem is that fast memory is very expensive so this cache must be quite small. The level 2 cache contains a much larger subset of recently accessed memory that cannot fit in the level 1 cache. It is faster than system memory but not as fast as level 1. How mucg all this improves performance depends a great deal on exactly what the CPU is doing.

It is important to understand that all of this is managed internally withing the CPU and even the OS cannot control it.

These caches greatly improve CPU performance. If the CPU requests data from memory that is in the level 2 cache, or even better in level 1 cache, there is no need to go to the slow system memory. All else being equal the larger the level 1 and level 2 caches the better will be performance. But "all else" is very rarely equal. There are many other factors that govern CPU performance. Evaluating how effective caching is in different CPUs is very difficult.

 

[Skylais]

Dating back to the 1980's system memory has been much slower than the CPU. Providing an adequate amount of system memory that matched the CPU in performance would be prohibitively expensive. Normally this would very seriously impact performance. To solve this problem all modern CPUs include a Level 1 and Level 2 cache. The level 1 cache contains the most recently accessed data. If the CPU requests data that is in the cache the access is very fast. The problem is that fast memory is very expensive so this cache must be quite small. The level 2 cache contains a much larger subset of recently accessed memory that cannot fit in the level 1 cache. It is faster than system memory but not as fast as level 1. How mucg all this improves performance depends a great deal on exactly what the CPU is doing.

It is important to understand that all of this is managed internally withing the CPU and even the OS cannot control it.

These caches greatly improve CPU performance. If the CPU requests data from memory that is in the level 2 cache, or even better in level 1 cache, there is no need to go to the slow system memory. All else being equal the larger the level 1 and level 2 caches the better will be performance. But "all else" is very rarely equal. There are many other factors that govern CPU performance. Evaluating how effective caching is in different CPUs is very difficult.

Wow how detailed, sounds like something i am reading out of my Cisco textbook right now.
Thanks, i am just wondering if i should avoid getting a specific cpu since it only has 1mb l2 cache. its dual core 3.3 ghz amd but then there is one that has more cache but its a bit more pricey and im unsure if 1mb will give me noticeable effects toward what i would do. Really it would be gaming (weak graphical games, minecraft, age of empires 3) and school work.

 

[kbrady1979]

Level 1 and level 2 caches are very important to performance. All modern processors have them. But there are numerous other important factors as well. If you could clarify the question a better answer can be provided.

okay well let's see. Say we have a dual core 3.3 ghz processor with 1mb l2 cache and then like a 3.0ghz proc single cored with 8mb l2 cache. ? What does the cache really do? and how much of a performance boost does it give?

Not enough to compensate for less cores.

 

[LMiller7]

Single core CPUs have a specific problem in desktop use. If that one core is running a CPU intensive thread any other process the user wishes to interact with will have to compete with it. This lowers the response time of the system and that is often more important than measured performance. With a CPU with 2 or more cores the chances of this happening are much reduced and response time improves.

Increasing the number of cores will always (within reasonable limits) improve performance. But you will quickly reach a point of diminishing returns where more cores provide no noticeable gains. Multiple cores only helps when there are several CPU intensive threads waiting to run and with most software that isn't going to happen very often. In a typical situation adding more cores simply means more cores waiting for something to do.

For desktop use you will want a dual core as a minimum. How much gain you will receive from more will depend on the software you are using.

 

[markaz]

I'm shopping for a CPU for a home built and looking at 3 processors. The caches vary in the stats and am curious in a comparison if one appears "better" than the others. I'm aware that cores is probably more significant, but I'm interested in the cache comparisons (and I've looked for L3 cache for #1 and #2 but cannot find them:

 

[AddRAM]

Of course the quad core is better.

List the models you`re looking at.