presence of register is and status of register is well known to processor than processor’s knowledge regarding cache..
Use of cache is implementation specific where as registers are used by processor as registers are nothing but part of processor..
Madhav Purohit answered
Lavin Deepak Sharma (anonymous)
Simply stated a register is faster and more costlier than cache. They both are used as buffers to store data for sometime while data is transfered between slower but cheaper memory devices like RAM, HDD.
Lavin Deepak Sharma answered
Saurabh Kalikar (anonymous)
register are used by ALU..register are at more interier side(logically) than cache.