HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management
找到SecondLevelDataCache,修改十進位L2 Cache值

不過改了似乎沒差(我是有改啦!! )

微軟有澄清過上面的那個值，在2000之後的OS是不需要修改的，改了可能會造成問題。

L2cache的開關在BIOS裡，至少我的是這樣。

以下擷取自微軟網頁
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. If the value of this entry is not 0, it uses this value as the L2 cache size. This entry is designed as a secondary source of cache size information for computers on which the HAL cannot detect the L2 cache.

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. SecondLevelDataCache can increase performance by approximately 2 percent in certain cases for older computers with ample memory (more than 64 MB) by scattering physical pages better in the address space so there are not so many L2 cache collisions. Setting SecondLevelDataCache to 256 KB rather than 2 MB (when the computer has a 2 MB L2 cache) would probably have about a 0.4 percent performance penalty.

如果你看不懂, 裡面最重要的句子就是
it is only useful for computers with direct-mapped L2 caches. Pentium II and later processors do not have direct- mapped L2 caches.
只有在電腦有direct-mapped(直接映射?)L2 Cache的時候有效, P2之後的處理器沒有direct-mapped的L2 Cache

既然你都不知道哪裡開啟，你又怎麼肯定『沒被開啟』？？

L2預設是一定會被開啟的,沒開啟肯定能感覺出變非常非常慢