First, read the English article below.

Before determining how much RAM you should purchase, it will be helpful to know how much RAM you already have installed in your computer. You can quickly check your installed RAM, regardless of what operating system you are using.  Windows - Press ⊞ Win+Pause to open your System Properties window. Your installed RAM will be listed in the System section. Mac - Click the Apple menu and select "About This Mac". Your installed RAM will be displayed in the Memory entry. There are several factors that will dictate how much RAM your system can support, including your operating system and motherboard limits:  If you are using Windows, a 32-bit version can support up to 4 GB, while a 64-bit version can support up to 128 GB. You can check what version of Windows you have by pressing ⊞ Win+Pause and looking for the "System type" entry. Even if your computer supports up to 128 GB, there's a good chance that your motherboard doesn't support that much. You'll need to check the documentation for your motherboard or run an online system scanner (Crucial.com has a good one) to see how much memory your motherboard supports. Mac users will need to check their documentation to see how much their computer support as it varies significantly from model to model. If you don't have the documentation anymore, you can look up the specs of your model on the Apple support site. See this guide for more details on determining the maximum amount of RAM your computer supports. RAM has gone through several revisions over the years. The standard these days is DDR4 RAM, but if you are upgrading an older computer, you may need DDR3, DDR2 or even DDR. If this is the case, you will likely want to consider upgrading the entire computer, as older types of RAM are getting increasingly expensive. You can determine what type your computer uses by referring to the documentation or running a tool like CPU-Z, a freeware utility that analyzes your system. RAM comes in a variety of different speeds. If there are multiple speeds installed, your entire system... 

Now, please write a short abstract for it in Vietnamese. Abstract:
Kiểm tra dung lượng RAM đang được cài đặt trên máy tính. Kiểm tra dung lượng RAM mà máy tính và hệ điều hành có thể hỗ trợ. Kiểm tra định dạng RAM mà bo mạch chủ hỗ trợ. Xác định tốc độ xung nhịp. Mua mô-đun RAM theo cặp. Bạn cần hiểu sự khác nhau giữa bộ nhớ laptop và máy tính để bàn.