Does 1MB L2 Cache really outperform the 512KB Cache?

[kxm9976]

hello,

Just wondering if its worth paying the extra $25 for large cache. It sure doesn't make a difference with P4. Northwood actually did better then Prescot in one of older Anand reviews.

thanks for the input

 

[Appledrop]

well.. on athlon64, cache doesnt play a major role, because of the ondie memory controller, but it will still bring very slight performance increase in games, etc.. but not noticable i doubt.

what you say about the p4 is sort of wrong. the reason northwoods often outperform the prescott with double the cache, is because they are faster, clock for clock... i think the prescott has a longer pipeline..
so the double cache on the prescott is more to even things up - a 512 prescott with the same speed as a 512kb northwood, well the northwood would win every time

 

[Acanthus]

The higher clocked 3400+ (the 512KB) is faster.

Edit: The Athlon-64 doesnt benefit much from the increased cache size (yes it does in certain situations for you graph happy bench junkies). The clockspeed benefits the CPU a lot more than the extra cache.

 

[element]

the extra cache gives about 5-10% increase (though closer to 5%depending on what you're using it for) but it costs much more. Not worth it.

 

[kamranziadar]

Yeah it outperforms 512KB easily by 15%, and helps you in the future for games.

 

[ViRGE]

Originally posted by: Acanthus
The higher clocked 3400+ (the 512KB) is faster.

Edit: The Athlon-64 doesnt benefit much from the increased cache size (yes it does in certain situations for you graph happy bench junkies). The clockspeed benefits the CPU a lot more than the extra cache.

Quoted for accuracy. There are 2 S754 3400+'s, the 2.2ghz 1MB, and the 2.4ghz 512K; the later one is faster in almost all cases.

 

[gobucks]

Faster speed means more to the A64 than cache size in most apps. Here is a good guide to how much to attribute to each thing: 1MB L2 ~= 150 PR points
200MHz clock speed bump ~=250 PR points
Dual Channel memory ~-300 PR points
start with the base configuration: no dual channel, 512KB L2, i.e. A64 3000+ @ 2GHz. Say you want to compare the 3200+ configurations.
Part 1: (754, Clawhammer) = 3000 + 150 (1MB L2) = 3150
Part 2: (754, Newcastle) = 3000 +250 (200MHz speed bump) = 3250
Part 3: (939, Winchester) = 3000 +300 (Dual Channel) = 3300

Winchester and Newcastle are the fastest, probably winchester is a bit faster overall, but it depends on the application. Clawhammer is slower, except in a few cache-hungry apps. This isn't perfect, but this is similar to how AMD should implement PR, since the 3 attributes are not equal in their benefits.

 

[Mik3y]

Originally posted by: kamranziadar
Yeah it outperforms 512KB easily by 15%, and helps you in the future for games.

that's not true. the 200mhz boost is there to make up for the loss of 512k of cache, since 1mb costs more then it benefits the cpu. because of amd's length of pipelines, 512k of cache has more meaning to amd then 512k of cache does for intel.

 

[uOpt]

Well, you understand what a cache does?

As long as the application ha most of its working set within 512 KB there is very few benefit going to 1024. Only if your applcations blows this cache there is an advantage. But most software developers who care about performance do test and benchmark on 512 KB cache chips, because that is what the overwhleming majority of customers has.

Just because your application is big and/or the developer doesn't care about cache effects doesn't mean the bigger cache buys you much as they can as well blow the 1024 KB cache, hitting main RAM.

From what I have seen lately, only Unreal Tournament is benefitting from going from a 512 KB to a 1024 KB L2 cache. The HL2 benchmarks indicate they hit main memory a lot, they will probably update their code somewhat.

BTW, the prescott is so different from the northwood you can't take that as an example. But there are plenty benchmarks comparing the Atlhlon 64 3400+ with 2.2GHz and 1024 KB cache with the 2.4 GHz with 512 KB cache one. The faster clockspeed pretty much always wins, except for UT.

 

[Comparisonman]

As most of us in here have said, more cache does not mean more speed. Of course, having a limited amount of cache will limit your speed, but once you get more than enough to handle the instructions that your computer sends to it, there isn't really a performance increase. So, as long as you have at least about 512k cache, go for the increased mhz in the processor.

 

[kxm9976]

I am gonna stick to the Newcastle core. That's seems to be the best match for the type of stuff I do.
THanks everyone for your input.

If you guys have time and are interested check out one of my last topics and tell me what you think about the system. Make sure you check out the latest one.

thanks to all

 

[WobbleWobble]

Originally posted by: kxm9976
Just wondering if its worth paying the extra $25 for large cache. It sure doesn't make a difference with P4. Northwood actually did better then Prescot in one of older Anand reviews.

This is a different comparison. There were other modifications made that lowered IPC but allowed the CPU to scale to higher speeds.