Does Cache on the new penryn really matter?

[Radio Monk33]

That is correct. Cache is very expensive. Adding more then you need would be suicidal for a processor company. It would also be suicidal for a processor company to build a processor that is significantly starved from not having enough cache.

Now I have not read the cold hard spec sheets of these processors yet as I don't have the time to put in the research but it is highly unlikely that Intel is short changing you. So i cannot say for certain if Intel and Apple are short changing their buyers in this case.

I must first define the term "throughput". Throughput is how much work the processor is getting done. Inside the processor there is Cache and there is CPU. Cache is memory and CPU is brains. Think of the Cache as an office desk and think of CPU as a secretary. The bigger the desk the more room she or he has to manage all her papers and work.
So the main idea is if you have a really smart secretary (CPU), then he or she can work optimally on a relatively small desk (Cache).

Thank you for an informative post! I love actually seeing well thought out explanations here with actual information, as opposed to the usual ranting, raving, spam, and personal stories.

 

[FreAk6767]

I am glad I was able to help you and hopefully others in the future.

I highly doubt you will see a significant or "worth mentioning" performance increase in the two models. I actually highly doubt that giving up your current MBP for a new one is really worth your troubles in my honest opinion.

I have the lower end model of the same MBP revision as you and I cannot tell a difference between it and my friends newer MBPs. I also believe the picture the LED screen's isn't as good as the lamp ones in yours and mine (when they are working properly with no yellowing or bands ).

I have never done any video editing or encoding but highly doubt upgrading your machine will give you a performance increase worth your troubles. The battery life isn't much different either from what I have seen.

Regardless, good luck in your decision.

Thanx for your great posts! Really cleared things up!

As I said before, I was gonna replace the HD with a 7200 and adding ram anyway. Given that I managed to sell the 2,33Ghz for a good price, getting a brand new model (with 7200 BTO and Ram from crucial) is nearly cheaper than doing this on my current MBP.

That's all. Of course, there's a new warranty too.
I hope the Led screen is not as bad as you say, compared to the ones we have in the previous Mbp.

For the troubles, I like installs... lol

 

[gr8tfly]

"Cache is nothing but a performance cruch for poor chip design."
- My computer architecture teacher.

If the CPU could access RAM (main memory) at the same speed it can access L2 cache, that statement might make some sense (my first thought was simply: inaccurate).

The problem with cache is balancing the difference in main memory access times verses cache lookup times (and its overhead). That's oversimplifying it, but that's the basic idea. So, yes, too much cache can actually slow things down, because it could take more time for a lookup.

There are other disadvantages of cache, but more to do with certain real-time applications.

 

[Animalk]

If the CPU could access RAM (main memory) at the same speed it can access L2 cache, that statement might make some sense (my first thought was simply: inaccurate).

The problem with cache is balancing the difference in main memory access times verses cache lookup times (and its overhead). That's oversimplifying it, but that's the basic idea. So, yes, too much cache can actually slow things down, because it could take more time for a lookup.

There are other disadvantages of cache, but more to do with certain real-time applications.

What you have said is correct but I suspect you have misunderstood my teacher's statement. He was not thinking of the interaction between the L2 cache and RAM, but rather the L2 cache and the L1 cache. He is saying that a large L2 (or even L1 if you think about it) cache is a nice way to make up for poor chip design (especially when it comes to Branch prediction).

For those who are not comfortable with all this hardware talk, if you refer to my previous example in this thread where the I compared the CPU and the Cache inside a processor to a Secretary and his/her desk in an office, you can think of the L2 cache as the desk and the secretary's hands (what he/she is currently working on) as the L1 cache. And RAM would be the mini-file cabinet under the desk.

 

[gr8tfly]

What you have said is correct but I suspect you have misunderstood my teacher's statement. He was not thinking of the interaction between the L2 cache and RAM, but rather the L2 cache and the L1 cache. He is saying that a large L2 cache is a nice way to make up for poor chip design (especially when it comes to Branch prediction).

For those who are not comfortable with all this hardware talk, if you refer to my previous example in this thread where the I compared the CPU and the Cache inside a processor to a Secretary and his/her desk in an office, you can think of the L2 cache as the desk and the secretary's hands (what he/she is currently working on) as the L1 cache. And RAM would be the mini-file cabinet under the desk.

Ah, makes more sense in that context. Taken at face value, though, it did seem odd coming from an instructor. I thought we were talking about L2, anyway....

 

[okgo]

I am glad I was able to help you and hopefully others in the future.

Another big thank you.
I have been trying for days to find a clear explanation of how the L2 cache affects performance.

 

[Dustman]

benchmarks say no.

 

[burningrave101]

There are several factors that play into effect when determining how much benefit you get from added cache and one of them is figuring out the latency. A lot of times when the cache size increases so does the latency. The whole point in on-die level cache is fast access and not so much storage capacity. If the latency is increased then the benefit from the larger cache may be somewhat negated at times due to the application you're running.

If you want to see a fair comparison as to how the T8300 vs T9300 compare you can look at Anandtech's review of the latest MBP's here:

http://www.anandtech.com/mac/showdoc.aspx?i=3246&p=10

The T9300 has a slight overall advantage across the board but it's not anything you're actually going to notice in real world usage unless you're sitting running CPU intensive tasks that take a period of time to complete. Normal PC tasks that most people run complete in a matter of seconds and so you're going to notice zero real world difference. Personally I don't think going from a 2.33Ghz to a 2.5Ghz is much of an upgrade, cache or no cache. And there is no real benefit to the 8600M GT 512MB. That card is crippled by a 128-bit memory bus so 256MB of VRAM is about all it's going to really make use of effeciently.

For roughly $450 USD the upgrade however is a farely decent one if you're getting 4 gigs of RAM, a 200GB 7200rpm hard drive, and a LED-backlit screen. Those three upgrades are worth far more than you will get from the CPU or GPU. I would just go with the 2.4Ghz T8300 and 8600M GT 256MB though cause you're really not getting any worthwhile upgrade on the higher model unless there is a discount on it to cut the difference in price.