In Windows 10, Performance tab/Memory button in Task Manager, what does the cache value mean?
In the picture below it says I have a cache of 1.3GB. Does it means RAM cache? CPU cache? Disk cache? File System cache? and how do I clear it.
In Vista and later the Cached value is the sum of the Standby and Modified lists as shown in Resource Monitor. This is RAM. The CPU cache is internal to and managed by the CPU and not shown in Task Manager. The file cache is RAM used to contain frequently accessed portions of disk files. It is not part of the Cached value and Task Manager shows nothing about it.
The Standby list is RAM and serves a dual role. It contains application data but has not been recently accessed. In fact much of it will never be used by the application again. If it is later needed the application can quickly reclaim it.
The data in the Standby list is also on the disk. This makes it possible to quickly reassign this memory to any other process that needs it. The details are complex and I will not describe them here.
The Modified list is RAM that contains data that has not yet been saved to disk. When that is done it will go to the Standby list. It's size is usually quite small, probably less than 50 MB on a 4 GB system. I will say no more about it.
Most of the Cached value is available memory and freely available to any process. This is much better than free memory which should be kept to the absolute minimum.
Cached memory is a major contributor to system performance and a high value is a good thing. Clearing it would almost always be bad idea and would negatively effect performance. Windows provides no user accessible means of doing so. There are utilities available that can do this but they are best left to those who have a thorough understanding of the implications.
As a general rule caches are best left alone. They are complex and would not have been developed unless they provided a valuable service.
I see nothing in the screenshot that would be a cause for concern.
You are on the "Memory" tab of Task Manager, so all the information there has to do with your system's memory (RAM). If you look at your CPU's specifications, you will see that we are a long ways away from having gigabytes of CPU cache.
The goal of caching in general is to increase performance by making resources available before they are needed; in this case, loading data into RAM that the kernel thinks may be useful in the future (which is not always correct). So even if there is a way to clear it, there is really no need to, and it would just fill up again. Also note that RAM is volatile, so the cache isn't kept when the system is not powered.