Most of them can be matched now, but try to buy the same frequency. There is usually a piece of paper on the memory stick.

It has trademark, memory type, memory frequency, memory size and other information.

Memory type: DDR DDR2 DDR3

Memory frequency unit is MHz: common ones are 266 300 533 667 800106613331666.

The unit of memory size is MB or GB: 32mb64mb128mb256mb512mb1g2g8g.

Usually the unit is not written on paper, but only a long string of numbers, such as DDRII5 12800.

It means DDR II 5 12MB 800MHz.

Of course, the memory stick installed on the computer is directly displayed on the screen with software everest, CPU-z and so on.