事件起因
我对电脑的使用的需求就是合上带走，打开操作，所以经常直接合上电脑放在电脑包里带回宿舍，有天从电脑包里拿出电脑的时候发现电脑显著变慢，打开任务管理器时发现CPU的频率被限制在0.79GHz，而我的CPU型号是i5-7300HQ的描述为：
Intel第七代KabyLake架构，BGA封装，四核四线程，支持Intel睿频加速技术，主频2.5GHz，L3缓存6MB。14nm制程，热设计功耗45W，单核睿频3.5GHz，全核睿频3.1GHz。
尝试自我解决一：还原系统
我以为可能是存在瞬时过热的情况导致的温度墙将我的CPU给降频了，但是并不能理解为什么在温度降低以后没有恢复。
所以我脑残的使用系统选项里面的还原选项还原了我的电脑，然而问题并没有解决
联系DELL客服：关闭睿频
尝试自我解决失败后，我于是直接联系了DELL的售后(400-881-2101)问题描述以后，售后人员的给出的问题解决方案是关闭XPS的睿频功能
重启的时候按F2，在performance界面的INTEL@tuboboost选项里关闭即可
更新BIOS可以解决吗？
期间我搜索到了XPS 15的BIOS最新版，寄希望于更新BIOS可以解决该问题，但是结果不尽如人意，并无法解决问题，所以我按照客服的说法关闭了XPS的睿频功能，但是问题依旧没有得到解决
售后维修
再次和DELL客服取得联系，客服人员也不清楚这样的情况如何解决，于是建议我前往DELL的售后点进行维修，我当然是不愿意前往维修点进行维修的，因为我始终觉得我的问题并不是硬件的问题，所以我打了售后维修的电话，询问这样情况他们是否遇到过，维修人员给予的否定的答案，并给出的他们认为的解决办法
- 重装系统
- 更换主板
我确认了还原系统和重装系统是不一样的之后，就选择了重装系统，但是依旧没有解决问题，但是我也觉得更换主板是我不可以接受的，硬件层面我并不认为是有问题的，所以我开始了自我解决的道路
尝试自我解决二：问题搜索
我在DELL的community里面看到有人也也提到了这个问题，并且在讨论中给出了解决的办法，就是给BIOS断电重启
Backstory
Since Christmas I have owned a Dell XPS 15 running Debian. It was unbelievably slow and laggy at first and I eventually chalked it up to an intel_pstate bug causing my CPU to be stuck at 800Mhz as I thought was confirmed by this thread that links to this kernel.org bug discussion.
However, over this timeline, I also installed Windows just to update the Thunderbolt firmware for my great USB-C experiment that I posted on here.
On a whim, I opened up task manager on Windows and noticed that the CPU on Windows was also stuck at 797Mhz. Okay, so not an intel_pstate Linux bug. wtf?
BIOS resets and BIOS + firmware updates to latest did not resolve the problem.
Stumbling upon the fix
I’ve been searching around all sorts of forums, bug reports, and subreddits for any mention of the Dell XPS and stuck or throttled frequencies. After a couple weeks of searching, I finally stumbled across this Dell Community thread.
You need to shutdown the PC, then open the bottom lid up (unscrew 10 torx t5 screws and 2 philips ph1 under the XPS plate) and disconnect the battery for 10-15 seconds, then reconnect it back. On my notebook it returned the speedstep back.
Verdict
In a last act of desperation, I purchased a Torx screwdriver set and tried the fix. And it worked! Both Windows and, with intel_pstate reenabled, Linux now scale the CPU correctly between 800Mhz and 3.20Ghz.
I also think my GPU must have been throttled because, as a photographer, I use Darktable under Linux and it was very, very slow even when I was using the ondemand governor for Linux. It’s now super snappy!
It has to be because of something that shows up in my BIOS logs that a user on the same Dell Community thread mentions:
…it was suggested that either a “bad” power supply or a “thermal” event may trigger this “safe” mode…
I did have a log entry of a bad power supply connected in early December. Clearing the logs did not fix it, only disconnecting the battery. It must be a hardware flag of some sort.
问题解决
我打开后盖，断掉电源，开机后CPU频率回复正常，问题解决
附上相关拆机链接：
https://www.mokeyjay.com/archives/1958
https://zhuanlan.zhihu.com/p/27590361
https://zhuanlan.zhihu.com/p/27695128
https://post.smzdm.com/p/571349/
https://www.reddit.com/r/Dell/comments/6qzc4y/xps_15_9560_undervolt_guide_wthrottlestop/
