Source : Free On-Line Dictionary of Computing

backside cache
     
         An implementation of {secondary cache}
        memory that allows it to be directly accessed by the {CPU}.
     
        Backside cache is used by {Apple Computers, Inc.} in their
        {PowerPC G3} processor.  Previous PowerPC processors used the
        {system bus} to access both secondary cache and {main memory}.
        In the PowerPC G3 a dedicated bus handles only {CPU}/cache
        transactions.  This bus can operate faster than the system bus
        thus improving the overall performance of the processor.
     
        The term apparently derives from the relocation of the
        secondary cache from the {motherboard} to the processor card
        itself, i.e. on the backside of the processor card.
     
        (1998-09-10)