Windows2000/xp series optimization misunderstanding

Computer shop news 1, modify the second level cache can not speed up XP In many XP optimization skills, a more popular saying is that Windows XP system requires users to manually open the CPU's L2 cache, in order to make the CPU play out Maximum efficiency. This is widely circulated, and one of the most used Windows system optimization softwares, "Windows Optimizer", holds the view that there is an option to optimize the CPU's L2 cache in its optimization settings bar. Let's first take a look at how this so-called optimization technique tells us. [Windows XP system, the CPU secondary cache is not turned on by default. In order to improve system performance, we can open it by modifying the registry or by using software such as "Windows Optimizer". Run the registry editor, expand the HKEY_LOCAL_MACHINE\\System\\CurrentControlSet\\Control\\Session Manager\\Memory Management branch, double-click "SecondLevelDataCace" in the right window, and then directly fill in the CPU of the current computer in the pop-up window. The level of cache capacity is fine. The Celeron processor's L2 cache is 128KB, and its value should be set to 80 (hexadecimal, the same below). PII, PIII, P4 are all 512KB L2 cache, should be set to 200; PIIIE (EB), P4 Willamette only 256KB L2 cache, should be set to 100; AMD Duron only 64KB L2 cache, should be set to 40; K6- 3 has 256KB L2 cache; Athlon has 512KB L2 cache; Athlon XP has 256KB L2 cache; Athlon XP (Barton core) has 512KB L2 cache. Using Windows Optimizer can also correctly set the CPU's L2 cache: Start Windows Optimizer, select "System Performance Optimization", in the "File System Optimization", the top is about the CPU L2 cache settings. Once you drag the slider to the appropriate location, save your settings and restart your computer. 】 Is this really the case? We found the following in Microsoft's knowledge base: The value of the SecondLevelDataCache key in the "HKLM\\SYSTEM\\CurrentControlSet\\Control\\Session Manager\\Memory Management" is only read in the Windows XP system from the Hardware Abstraction Layer. The data of the SecondLevelDataCache key is read only when the CPU L2 cache (L2) fails. And the meaning of the SecondLevelDataCache key value = 0 is 256KB for the second level cache. Original (english) In a knowledge base article we also found "Do not change the SecondLevelDataCache entry", in this case, pointed out in the article that some third-party data claimed to modify the value of the SecondLevelDataCache key can improve system performance is not correct . The value of the L2 cache is detected by the operating system and is completely unaffected by the SecondLevelDataCache value. Original (english) From the Microsoft Knowledge Base article we can see that the so-called Windows XP system requires users to manually open the secondary cache is wrong. The Windows XP system reads the secondary cache value of the CPU based on the hardware abstraction layer. The value of SecondLevelDataCache is read only when the read fails, and the default value of 0 of SecondLevelDataCache represents the meaning of the second level cache is 256KB instead of closing. Therefore, the secondary cache of the CPU is turned on at any time, and the user does not need to modify it. 2, remove 20% of the QoS speed will be fast? In a variety of Windows XP optimization articles, there is an article about QoS can be described as a long history, from the beginning of Windows XP, it began to spread, until now It appears frequently in various Windows XP optimization articles. So what is this skill? Let's take a look at one of the optimization techniques. “ In the "Run" dialog box, type “gpedit.msc” command to open the "Group Policy" window, and then from the "Administrative Templates", find the "Network" project, there is a ". ;QOS packet scheduling” item, you can see a “Restrict bandwidth reserved” item under the “Settings” column on the right side of the window. Double-click the item to see the bandwidth here. The limit is 20%, we just change it to “enabled” and change the "bandwidth limit" value to “0%” to maximize bandwidth usage. ” Is the fact that Windows XP keeps 20% of the bandwidth and does not use it for us? After changing 20% ​​to 0%, is it really possible to speed up the Internet? The answer is of course no. Let's first look at how Microsoft explains this problem. The problem with QoS in Microsoft's KB316666 knowledge base is explained as follows: As with Windows 2000, in Windows XP, programs can also take advantage of QoS through the QoS application programming interface (API). All programs can share 100% of the network bandwidth, with the exception of programs that require bandwidth priority. Other programs can also use this "reserved" bandwidth, except for the requestor that is sending data. By default, the program reserves a bandwidth that is up to 20 percent of the basic link speed of each interface on the terminal computer. If the amount of data sent by a program that reserves bandwidth does not completely run out of bandwidth, the unused portion of the reserved bandwidth can be used for other data streams on the same host. It is clear in Microsoft's KB316666 that many published technical articles and newsgroup articles have repeatedly mentioned that Windows XP generally reserves 20% of the available bandwidth for QoS. Let us first clarify what the true meaning of QoS is. The Chinese meaning of QoS is: the quality of networked services. Specifically, it refers to various communication or program type prioritization techniques applied across the entire network connection. The existence of QoS technology is to obtain better quality of networked services. QoS is a set of service requirements that the network must meet to ensure proper service level data transfer. The implementation of QoS enables network applications such as IPTV and network music to use network bandwidth most efficiently. Because it ensures that a certain level of assurance has sufficient network resources, it provides a shared service level similar to a private network. It also provides a means of notifying the availability of application resources, allowing applications to modify requests when resources are limited or exhausted. The goal of introducing QoS technology in Windows XP systems is to establish a guaranteed transport system for network communications. From the above Microsoft's interpretation of QoS, we can know that by modifying the 20% of QoS to 0% in the Group Policy Editor, the goal of optimizing network performance is not achieved. The modified 20% parameter in Group Policy refers to the maximum amount of bandwidth that can be used when the QoS API writer needs to access the network. If we set it to 0%, it means that the application written with the QoS API must not be used. Without competing for limited bandwidth with other applications, the possible consequence is that data that requires priority communication does not get priority. From this point of view, changing 20% ​​of QoS to 0% will not only have no benefit but also cause some real-time network applications to not use network bandwidth effectively. So this so-called optimization technique can be said to be a misleading.