how important is L2 cache size?

[Myriadd]

Hi All,

I'm patiently waiting for the first retail NForce4 - SLI board to come to market, so that I can put together my first new machine in over 4 years. I'm wondering if people could weigh in on the importance of the L2 cache size. Specifically, I'm looking at possibly getting an Athlon FX-55 or 4000+, and getting *one* 6800 GT, or going with an Athlon 3500+, and using the money saved for a second 6800 GT (my original idea was to get a second one down the line a bit, when they become somewhat more affordable). The first option features a better clock speed (a feature I'm not really married to), and a 1 Meg L2 cache, whereas the second has only a 512 L2 cache. The rig is strictly for gaming.....EQ2 is a graphically demanding mistress.

Any thoughts?

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[stelleg151]

welcome to anandtech forums. Are you planning on ocing? That will decide my answer for you. If you want to OC, I would get any of the winchesters or the fx-55, if you arent, any of those choices are good, although I would recommend the 3800+ over the 4000+, as there is little difference in performance and over 100 dollars difference in price. The L2 cache size doesnt have a very big impact on performance.

 

[Rike]

Go with your second choice, two vidcards and then OC the 3500+. Thermalright xp-90 or xp-120 for air cooling. The top of the line A64 don't scale in performance with price. More bang for your buck with the 6800GTx2.

 

[Myriadd]

Thanks for the advice. I've not overclocked any rig before, but all the research that I've done (a great deal, given that I've been waiting to buy this system for months ) suggests that if ever I was to start, the ideal jump off point is the 90 nm Winchester core. Assuming one does the research and gets adequate cooling, how safe is OCing? Can you recommend any solid guides (other than anything that can be found on this site)?

Thanks.

 

[SadisticOne]

Overclocking can put the PCI/AGP bus out of spec if you can't lock it. The new nforce4 boards *should* allow this, but its not guaranteed. Don't adopt til you've seen a few successes for what you want to do.

A big caveat is with SATA drives... these are more susceptible to problems with overclocking.

DDR can also be problematic. Choose wisely.

 

[uOpt]

A lot of benchmarks were comparing recent Athlon 64 with and without dual-channel memory and with 512 and 1024 KB cache.

The result was that for most applications and most games the clockspeed was most improtant, only Unreal seems to like a cache bigger than 512 but as small as 1024 KB, and only HL2 seems to benefit from dual-channel RAM.

Most software developers are careful to target a certain cache size. Since 512 KB is predominant these days you can expect most carefully engineered programs to try to fit into 512 KB cache.

If you go to a 4 MB cache like on the P4 extremes you see more of a speedup, interestingly. This might have to do with P4 specifics, or it may be that the software access patterns fall into a 4 MB, but not a 1 MB window.

Last but not least keep in mind caches are not very flexible, not every cache emory cell can back every RAM memory cell. There's always some overhead, i.e. wasted cache memory.