L2 Cache disabled??

[The_Other_One]

Here's something I found on another forum I thought you guys might be interested. It seems, by default, windows disables your L2 Cache, or at least doesn't use it all...

1) Go to your start menu and select run
2) in the pop up window type REGEDIT
3) Select and open HKEY_LOCAL_MACHINE
4) Select and open SYSTEM
5) Select and open CurrentControlSet
6) Select and open Control
7) Select and open Session Manager
8) Select and open Memory Management
9) Select SecondLevelDataCache in the right hand menu

Right click on the highlighted SecondLevelDataCache and select modify. In the window that pops up select decimal and put in the amount of L2 that is on your cpu.

10) Restart

I'm about to try it myself... Realize I'm only on my laptop with 256KB cache right now, so I probably won't notice much, if any difference. However, my Athlon at home has 1024KB. Hopfully it'll at least make a difference there

--Edit--
Just a quick update, there might be a small increase in performace on my lappy, but it's hard to say without any accurate benchmarks as well. Again, tommarow I'll try it on my desktop.

 

[Shady]

so i put the L2 Cache value in decimal in Kilo bytes ? or bytes ?

 

[elmarcorulz]

Here's what i got from a different site

You can enable the Level 2 Cache with the follow registry key: HKEY_LOCAL_MACHINE => SYSTEM => CurrentControlSet => Control => Session Manager => Memory Management

SecondLevelDataCache
for 256kB Level 2 Cache = 0
for 512kB Level 2 Cache = 200
for 1024kB Level 2 Cache = 400

NOTE: Level 2 (L2) CPU cache size can be sized this way, ONLY IF using earlier CPUs: Intel (and compatibles) 386, 486, Pentium, Pentium Pro, AMD K5/K6/K7, Cyrix, etc, with off-chip L2 cache SRAM memory (external, off the CPU die). If using newer CPUs: Intel Pentium II/III/IV/Celeron/Xeon, AMD Athlon/Duron/Thunderbird, etc, with on-chip L2 cache SRAM memory (internal, on the CPU die), L2 cache size can NOT be altered!

 

[Shady]

ok i'm confused

 

[elmarcorulz]

Well double click the "Secondleveldatacache" and type in 200. The Value next to it automatically adjusts to 512. Same happens if you type 400, it goes 1024

 

[The_Other_One]

elmarcorulz - Learn your Hex conversions 200 = 512. If you noticed I said "select decimal", so either way it's the same.

The only thing, though, if you put 100, you get 256 as the value, so I'm not sure what the site was saying about just leaving it as 0... Hmm...but I suppose this won't do anything. I'll still try it when I get home. Perhaps I'll even try it on my PIII. I should notice a difference by how they're talking.

 

[Shady]

so it's true it won't work for on die cache ?

 

[elmarcorulz]

elmarcorulz - Learn your Hex conversions 200 = 512. If you noticed I said "select decimal", so either way it's the same.

I didn't say you were wrong, all i did was make it easier for people who don't know hex to enable it.

 

[Geoff]

wait, so if i have 4MB of L2 Cache, would i put in 4096?

 

[Shady]

wait, so if i have 4MB of L2 Cache, would i put in 4096?

in decimal yes
and 1000 in hex
but the question is
will it work ?
they say it's only for external cache

 

[Cromewell]

It's in decimal, but I'm pretty sure there is no effect. Cache is a hardware prefetch, the only way to disable it is via the BIOS.

"0" in registry entries, esp. under the MemoryManagement key, usually tells the system "do your own default calculations based on actual hardware", not "force to a special value for one type of hardware".

edit: a little more info:

You should only consider editing the default value if you are running computers with direct-mapped L2 caches. Pentium II and later processors do not have direct-mapped L2 caches. A slight performance improvement (two percent) can be detected in older computers (486 and earlier) with memory of 64 MB and more due to the fact that physical pages are distributed better in the address space, reducing L2-cache collisions. However, defeating the operating system’s default behavior and setting the value of the SecondLevelDataCache to 256 KB rather than 2 MB when the computer has a 2 MB L2 cache reduces performance slightly.

 

[Geoff]

I tried it, and all it did was lower my test score 1 point

 

[The_Other_One]

*nods* I didn't see the info from the site when I first got this, so it seems it's a waste of time... However, it just might work with that PIII. Now that I'm out of school, maybe I'll give it a shot later.

 

[Cromewell]

I wouldn't bet on it working. A Pentium 1 or older (win9x should still have that setting) might get some slight performance increases.