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December 31st, 2003 06:00
How to maximize your level 2 cache.
Microsoft Knowledge Base Article - 183063
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager \Memory Management\ SecondLevelDataCache
SecondLevelDataCache records the size of the processor cache, also known as the secondary or L2 cache.
If the value of this entry is 0, the system attempts to retrieve the L2 cache size from the Hardware Abstraction Layer (HAL) for the platform.
If it fails, it uses a default L2 cache size of 256 KB.
I will translate.
If the value of the Secondlevelcache is zero.
The system tries to access this registry key as though it were larger than zero first.
If the system finds that the registry key is zero, it will use that size for secondleveldatacache.
The zero used in this registry key is really 256 Bytes.
Now for the scarry part.
Microsoft makes this registry key zero (256 Bytes), on ALL nt kernel operating systems.
And in doing so limits the processor secondleveldatcache to 256 Bytes.
To use a secondleveldatacache larger than 256 Bytes.
You have to edit the nessessary registry key.
I have 512 Bytes secondleveldatacache.
So I put Decimal 512, Hexidecimal 200. Instead of zero, in that registry key.
If you have a pentium 4 extreme edition processor with 2 megaBytes secondleveldatacache.
You put Decimal 2048, Hexidecimal 800, instead of zero in this registry key.
Here is a calculator to see for yourself.
http://www.speedguide.net/conversion.php
To get to this registry key.
First press the start button.
Then press the run button.
Then type regedit and press ok.
Now go and follow this path
HKEY_LOCAL_MACHINE\
SYSTEM\
CurrentControlSet\
Control\
Session Manager \
Memory Management\
SecondLevelDataCache
I'll summarize with a quote from Microsoft Knowledge Base Article - 183063
"Setting SecondLevelDataCache to 256 KB(0) rather than 2 MB (when the computer has a 2 MB L2 cache) would probably have about a 0.4 (40%)percent performance penalty."
What this registry key is set at has real performance results.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager \Memory Management\ SecondLevelDataCache
SecondLevelDataCache records the size of the processor cache, also known as the secondary or L2 cache.
If the value of this entry is 0, the system attempts to retrieve the L2 cache size from the Hardware Abstraction Layer (HAL) for the platform.
If it fails, it uses a default L2 cache size of 256 KB.
I will translate.
If the value of the Secondlevelcache is zero.
The system tries to access this registry key as though it were larger than zero first.
If the system finds that the registry key is zero, it will use that size for secondleveldatacache.
The zero used in this registry key is really 256 Bytes.
Now for the scarry part.
Microsoft makes this registry key zero (256 Bytes), on ALL nt kernel operating systems.
And in doing so limits the processor secondleveldatcache to 256 Bytes.
To use a secondleveldatacache larger than 256 Bytes.
You have to edit the nessessary registry key.
I have 512 Bytes secondleveldatacache.
So I put Decimal 512, Hexidecimal 200. Instead of zero, in that registry key.
If you have a pentium 4 extreme edition processor with 2 megaBytes secondleveldatacache.
You put Decimal 2048, Hexidecimal 800, instead of zero in this registry key.
Here is a calculator to see for yourself.
http://www.speedguide.net/conversion.php
To get to this registry key.
First press the start button.
Then press the run button.
Then type regedit and press ok.
Now go and follow this path
HKEY_LOCAL_MACHINE\
SYSTEM\
CurrentControlSet\
Control\
Session Manager \
Memory Management\
SecondLevelDataCache
I'll summarize with a quote from Microsoft Knowledge Base Article - 183063
"Setting SecondLevelDataCache to 256 KB(0) rather than 2 MB (when the computer has a 2 MB L2 cache) would probably have about a 0.4 (40%)percent performance penalty."
What this registry key is set at has real performance results.
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Denny Denham
2 Intern
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18.8K Posts
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January 1st, 2004 03:00
Of course I'm speaking tongue-in-cheek. Microsoft made a statement which clearly states that the performance hit is 0.4 percent. According to the originator of this thread, this particular usage is incorrect because they meant 40%. Since he is convinced that MS is incorrect I assumed that he would take them to task for the error.
Without a numerical value, I noted that in a discussion of this topic here the authors state, "Despite the technical logistics of this model, the fact remains that numerous accounts exist of users claiming that after setting this tweak, they received a serious boost in performance. Our tests revlealed that the tweak made absolutely no difference on PII or PIII processors."
msgale
2 Intern
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2.5K Posts
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January 1st, 2004 04:00
Denny thanks for the link, I found it fastinating, however at 1:30 AM my eye lids are really drooping, so I will re-read it tomorrow without the fog. I am glad I took Hardware 101, actually 603, so I can undersatand the author. I actually remember most ot the terms for five years ago. Happy New Year.
b11ng00
10 Posts
0
January 1st, 2004 07:00
However, if you wish to save your system the HAL call, and just supply the accurate L2 cache size (or preempt an unlikely HAL error), feel free to set the static value for your processor. Or, if you still have a PI (heaven forbid), continue on.
There's no harm in setting it to your cache size in the registry just in case the HAL fails.
Thank for the link.