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So recently I've been tweaking my computer's registry for its Memory Management. I know its a bad thing to do to edit your registry without knowing what it may cause to your system but i've only touched a specific registry value which is the SecondLevelDataCache in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management

I've "accidentally" set its value to 512 Hexadecimal(1298 decimal) instead of 512 Decimal. My CPU's L2 Cache can only do 2x256 KB(Intel I3 2nd Gen 2330M).

So far I've seen faster responses from the system when I set it on 512 Hexa.

Not only that, I've also tried playing games and running applications and also observed better performance from them overall.

And now my question is, what might be a problem later on for this setting if I left it on? What might it cause to my hardware/OS if it were to be left like that that?

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  • This Microsoft support page says that changing that registry value is only necessary if the HAL doesn't the L2 cache value. In fact this TechNet page confirms that. The performance increase is most likely coming from something else or is placebo.
    – user487867
    Nov 7, 2017 at 12:06
  • Level 1, 2, and 3 caches are hardware caches found on the CPU, They cannot be changed. What you are seeing is a stored value of what that cache is. Changing that value does not change the cache. On a side note, on very old PCs, level 3 caches were optional (if present at all) and found on the motherboard and could be physically changed.
    – Keltari
    Jan 2, 2023 at 19:43

2 Answers 2

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According to canonical source, the SecondLevelDataCache entry has no effect on performance. As a computer science bachelor I'm aware that modern CPU caches are invisible (transparent) to operating systems, optimizing RAM access automatically.

You may never know if you have really observed a performance "boost". Have you run any benchmarks and compared the result?

Nevertheless, keeping your modified value of SecondLevelDataCache probably does no harm to your hardware and user experience.

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  • If bench marking counts as: a faster time to load after logging in and loading up the desktop, applications and games run more smoothly... Then i guess i have observed a boost in performance(but as another comment said, its not very noticeable but it did improve)
    – Xenos29
    Nov 7, 2017 at 12:19
  • Benchmarking is more difficult than it seems and this appears to be a particularly difficult case. You would need to take many measurements under strictly controlled conditions with a reboot between each one. Boot time and application load time is subject to all kinds of other factors, most of which are very difficult to control. It would take a great deal of time. Otherwise I would consider the results to be of very questionable validity.
    – LMiller7
    Nov 7, 2017 at 22:22
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Windows will use the value here IF it cannot resolve the L2 cache size from the HAL (Hardware Abstraction Layer). Windows CAN get this value through HAL 99.9% of the time. If it can't, the default value of 0 will result in Windows thinking the L2 cache is only 256K. IF Task Manager (performance tab) shows L2 as "0", THEN this tweak is invalid. IF Windows didn't care about the L2 size, this registry entry wouldn't exist.

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  • This answer to a 5 year old question with an accepted answer would benefit from supporting references in order to understand if it is correct and adds anything.
    – Blindspots
    Jan 2, 2023 at 19:36

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