Why can CRC detect more errors than simple Checksum?
There are two purposes a CRC can identify more errors than a simple Checksum.
1. Since an input bit is shifted by all three registers, a single bit of the message influences the resulting CRC in dramatic manners.
2. Hardware utilizes feedback in that output from the leftmost shift register influences each exclusive or unit, the effect from a particular bit of the message cycle by the shift registers more than one time.