L2 cache settings

[shiato storm]

I read somewhere, just in passing and god knows where it was now, that Windows sometimes does not correctly utilise the L2 cache so just wondering where to set it to? and what value, I'm right in thinking its 512k for the AMD64 3000+ ?

[so, whats 1mb that I see ever so often - is that the fx55 chip?]

[Rave]

Whetever you've read is rubbish. The only thing you can do to affect processor cache perfomance is disable it in the motherboard bios.

Rich :¬)

[shiato storm]

so nothing about going into regedit and making sure its all ok?

[Mulda]

Allegedly Windows is optimised for 256k L2 cache, adding/changing registry settings can 'correct' the optimisation but I am yet to be convinced:

For 1Mb:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SessionManager\MemoryManagement]
"SecondLevelDataCache"=dword:00000400

For 512k:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SessionManager\MemoryManagement]
"SecondLevelDataCache"=dword:00000200

[shiato storm]

ah yes, thats what I was going on about

[Butcher]

FYI:

This is not related to the hardware; it is only useful for computers with direct-mapped L2 caches. Pentium II and later processors do not have direct- mapped L2 caches

The value has no effect on Athlon 64s as they have a 16-way set associative cache, not direct mapped.
BTW if you don't know what a set associative vs direct mapped cache is you have no business chancing this sort of value.

[shiato storm]

right o...i'll leave it well alone then
cheers

[aidanjt]

that windows reg tweak is regarding windows understanding of your hardware. the Default is for 256kb cache, windows is suppose to autoadjust this value to your processors real cache, however doesn't always do it.

[Butcher]

that windows reg tweak is regarding windows understanding of your hardware. the Default is for 256kb cache, windows is suppose to autoadjust this value to your processors real cache, however doesn't always do it.

It doesn't matter if it does or not. The parameter is there so that windows can tweak internal allocations to avoid cache thrashing due to aliasing. This is only an issue for CPUs with direct mapped caches. Modern chips have set associative caches so the parameter makes NO DIFFERENCE.

[weebroonieuk]

Sir Yes Sir !

[Butcher]

Heh, sorry to sound a bit forceful there, just misinformation about this keeps getting spread around, so it's best to make sure people know the facts.

[aidanjt]

i know i know, i read all reg tweaks from microsoft even before i try them myself, i was expanding a little.
i wouldn't say anything if i thought my explaination would hurt somebody