Write Through. After writing in cache memory, main memory is updated too inmediatly to mantain reliability
Write Back After writing in cache memory a flag bit called dirty bit is set. When this value need to be replaced that bit is check, if it is set then the value is taken to main memory
当CPU采用高速缓存时,它的写内存操作有两种模式,一种称为“穿透”(Write-Through)模式,在这种模式中高速缓存对于写操作就好像不存在一样，每次写时都直接写到内存中，所以实际上只是对读操作使用高速缓存，因而效率相对较低。另一种称为“回写”(Write-Back)模式，写的时候先写入高速缓存，然后由高速缓存的硬件在周转使用缓冲线时自动写入内存，或者由软件主动地“冲刷”有关的缓冲线。