what difference does level 2 cache make?

[PSUstoekl]

so, i see a bunch of these processors distinguish themselves price-wise based on two things, usually- clock speed and L2 cache. so, wtf is this cache business?

 

[Cooler]

After 1 Mb its you dont see a major differnce.

 

[atybimf]

Don't wanna jack the thread, but would the 1MB L2 cache of the 3700+ be worth the money over the 3500+ with the 512KB L2 cache?

 

[Varun]

Cache is very very fast memory where data is stored for use. The L1 cache is the first place the CPU tries to get data from. CPUs like the Athlon and Athlon 64 have a relatively large L1 cache.

L2 cache is the next step before RAM - slightly slower than L1 but always bigger. If L2 cache is large enough an entire executable can fit in it and be run extremely fast.

The next step is generally main memory, which runs much slower than the CPU (CPU=GHz, RAM = MHz).

Of course the final step is the hard drive which is incredibly slow. Hopefully you don't need to hit the hard drive much once the program is loaded...

Some CPUs have Level 3 cache as well, which is just another stop along the way after L2 and before RAM.

 

[atybimf]

so do you think that getting the 3700+ for its 1MB L2 cache would be wise? or should i save money and get the 3500+ that's the same speed but with a 512KB L2 cache.

 

[ahock]

then by all means why not make L1 larger? What is the difference between L1 and L2 in terms of architecture? All I know is that these are just SRAMs.....

 

[Varun]

Larger caches are both slower and have better hit rates. To ameliorate this tradeoff, many computers use multiple levels of cache, with small fast caches backed up by larger slower caches.

 

[SlowSpyder]

L2 cache is the next step before RAM - slightly slower than L1 but always bigger.

Not to nitpick, but the Duron actually had a bigger L1 cache then L2 cache. 128K L1 and 64K L2.

 

[Varun]

Originally posted by: SlowSpyder

L2 cache is the next step before RAM - slightly slower than L1 but always bigger.

Not to nitpick, but the Duron actually had a bigger L1 cache then L2 cache. 128K L1 and 64K L2.

You're nitpicking!

The only reason that works is because the Athlon is one of the CPUs that doesn't duplicate it's L1 in L2.

 

[Buck Naked]

Someone explained it this way to me before.
L1 would be a stack of papers on your desk
L2 would be a ref books in a desk drawer
RAM would be like a local library
HDD would be like library of congress

You want the info you need faster closer to you.
On the other hand you don't want the whole library on you desk, because it would take to long to look through.

 

[EightySix Four]

wow, that's possible the best description I've heard yet

 

[thecoolnessrune]

Originally posted by: Buck Naked
Someone explained it this way to me before.
L1 would be a stack of papers on your desk
L2 would be a ref books in a desk drawer
RAM would be like a local library
HDD would be like library of congress

You want the info you need faster closer to you.
On the other hand you don't want the whole library on you desk, because it would take to long to look through.

But what about people like me who have a mountaind of papers on their school desk all the time. I must be one of those 9MB cache Itanium 2's lol.

 

[cw42]

Originally posted by: Buck Naked
Someone explained it this way to me before.
L1 would be a stack of papers on your desk
L2 would be a ref books in a desk drawer
RAM would be like a local library
HDD would be like library of congress

You want the info you need faster closer to you.
On the other hand you don't want the whole library on you desk, because it would take to long to look through.

haha that's awesome. But how come we don't just have more L1 cache since it's closer/faster for the CPU?

 

[ssvegeta1010]

Originally posted by: cw42

Originally posted by: Buck Naked
Someone explained it this way to me before.
L1 would be a stack of papers on your desk
L2 would be a ref books in a desk drawer
RAM would be like a local library
HDD would be like library of congress

You want the info you need faster closer to you.
On the other hand you don't want the whole library on you desk, because it would take to long to look through.

haha that's awesome. But how come we don't just have more L1 cache since it's closer/faster for the CPU?

Because, as Buck said, adding more papers on your desk would make them take longer to look through. (SRAM technology is not developing fast enough to allow larger fast caches)

 

[Agnostos Insania]

If I may minorly threadjack, how important is the size of L2 caches for dual cores?

AMD 64 X2 4200+ (L2 Cache is 512kb x 2)
AMD 64 X2 4400+ (L2 Cache is 1mb x 2)

There's a 97 dollar difference and to my untrained eyes they seem pretty much identical except for the L2 Cache size.

 

[cw42]

Originally posted by: Agnostos Insania
If I may minorly threadjack, how important is the size of L2 caches for dual cores?

AMD 64 X2 4200+ (L2 Cache is 512kb x 2)
AMD 64 X2 4400+ (L2 Cache is 1mb x 2)

There's a 97 dollar difference and to my untrained eyes they seem pretty much identical except for the L2 Cache size.

did u read this thread at all? start from the top, and work your way down...

 

[Agnostos Insania]

Originally posted by: cw42
did u read this thread at all? start from the top, and work your way down...

Want to share some of your arrogance with the rest of the children? I think there are some kids in Africa that don't quite think they're ready for godhood yet.

I asked if there was a difference for dual cores, since they're different from single cores? Maybe the L2 Cache is more important... less important? Forgive me for not being a l337 mindreader like yourself. Ahem, I mean "urself".
FYI: Dual = Two. Normal Proc = One.

You can send me $300 for that lesson.

 

[Vegitto]

Originally posted by: Agnostos Insania
If I may minorly threadjack, how important is the size of L2 caches for dual cores?

AMD 64 X2 4200+ (L2 Cache is 512kb x 2)
AMD 64 X2 4400+ (L2 Cache is 1mb x 2)

There's a 97 dollar difference and to my untrained eyes they seem pretty much identical except for the L2 Cache size.

It depends on what your budget is, and what you're going to do with it. If you're a gamer or a power user (encoding or imaging), then yes. If you're just for allround use, it's more of a budget thing. If you've got money left, spend it on more RAM. Still got money left? Get a better graphics card. If money isn't an objection (and I bet it is), THEN get a processor with the larger cache.

Bottom line: Can you justify the cost difference to yourself? The performance difference is 2-9%.

BTW, don't threadjack, please. Thought I'd say it at the end, don't wanna be an ass .

 

[ribbon13]

Originally posted by: atybimf
Don't wanna jack the thread, but would the 1MB L2 cache of the 3700+ be worth the money over the 3500+ with the 512KB L2 cache?

Yes.

 

[SickBeast]

Originally posted by: ribbon13

Originally posted by: atybimf
Don't wanna jack the thread, but would the 1MB L2 cache of the 3700+ be worth the money over the 3500+ with the 512KB L2 cache?

Yes.

The new Opteron 144/146 chips are cheaper and better than both of those, and they have 1mb cache.

 

[Agnostos Insania]

Originally posted by: Vegitto
It depends on what your budget is, and what you're going to do with it. If you're a gamer or a power user (encoding or imaging), then yes. If you're just for allround use, it's more of a budget thing. If you've got money left, spend it on more RAM. Still got money left? Get a better graphics card. If money isn't an objection (and I bet it is), THEN get a processor with the larger cache.

Bottom line: Can you justify the cost difference to yourself? The performance difference is 2-9%.

BTW, don't threadjack, please. Thought I'd say it at the end, don't wanna be an ass .

Thank you. I didn't think it was much of a threadjack as it is concerning the L2 cache.

 

[Varun]

Originally posted by: Agnostos Insania
If I may minorly threadjack, how important is the size of L2 caches for dual cores?

AMD 64 X2 4200+ (L2 Cache is 512kb x 2)
AMD 64 X2 4400+ (L2 Cache is 1mb x 2)

There's a 97 dollar difference and to my untrained eyes they seem pretty much identical except for the L2 Cache size.

It's a tough call to say if it is worth the cash (pun) or not. More L2 cache is going to help a bit in all situations, however depending on application it can make quite a difference. If the main chunk of code can all fit in the L2 cache then the performance is going to be quite a bit better than the smaller cache. The problem is, it is really application dependent. Also, if the program can all fit in 512k Cache, then the performance will be pretty much identical.

This goes for single and dual core, they both operate the same. I'm not sure if both cores can use both caches or not though.

 

[WhoBeDaPlaya]

Quite a bit. Take a look at X-bit Labs' Sempron 3400+ review. They have an OC'ed Sempron 3400+ (2.6GHz, 256KB L2) getting close / beating an A64 3800+ (2.4GHz, 512KB L2). That's why the Sempron 3100+ with just 128KB of L2 is so horrible.

 

[anandtechrocks]

If you want to read something really interesting on this subject check out this guy's post on his experiences between a Vience (512 KB cache) and a San Diego (1 MB cache):

3700+ San Diego VS. 3200+ Vience

He clocked the processors to the same speed and did a great job in my opinion. He compared performance in a whole bunch of tests and did other test like temperature, etc.


Here is another set of test by the same user:

San Diego VS. Vience