If you're experiencing worse-than-normal performance in games, or the system is sluggish when moving between menus, clearing the system cache may help. This will be most effective with older Xbox 360 games. Clearing the system cache will not delete any of your games, save files, or media. It will delete any installed game updates, so these will need to be downloaded again when you play the game next. This will open the Guide menu. You'll see various settings categories. You'll see all of your connected storage devices. This will open the "Device Options" menu. It doesn't matter which storage device you select, as you'll be clearing the entire system's cache. The cache will be deleted, which should only take a few moments.

TL;DR in Vietnamese:
Xóa bộ nhớ đệm nếu bạn gặp rắc rối với Xbox 360. Nhấn nút Guide trên tay cầm Xbox. Chọn "Settings" > "System Settings". Chọn "Storage". Tô đậm thiết bị lưu trữ bất kỳ và nhấn nút "Y" màu vàng. Lựa chọn "Clear System Cache" (Xóa Bộ nhớ đệm Hệ thống) sau đó xác nhận.