A co-hosted cyclical redundancy check (CRC) calculations system is arranged to use a processor to generate initial addresses for reading the data from a mirrored device that has address ranges over which a CRC result is to be calculated. An memory mapping unit detects when the initial address falls within an address range over which the CRC result is to be calculated. A read snoop unit snoops the data read from a mirrored memory that has data stored using a mirrored address. A CRC co-generator receives the snooped data read from mirrored memory and uses the snooped data read from the mirrored memory to calculate the CRC result.