System-on-chip and acceleration method for system memory accessing

An acceleration technology for accessing system memory, which provides translation agent hardware that calculates the physical address of the system memory based on an access request issued from the device end. The translation agent hardware has a cache memory that stores information to speed up the calculation of the physical address. Each cache line corresponds to a last-recently used (LRU) index value, and the cache line with the greatest LRU index value is preferentially released to be reassigned. A counter counts a count value to show an isochronous caching demand. LRU index values of cache lines assigned to non-isochronous caching are kept not lower than the count value, and thereby isochronous caching takes precedence over non-isochronous caching.