These are the topics of Computer Architecture and Organization which must not be left unprepared . 
- Flynn's Classification
 - MIPS
 - Cache Memory
 - Types of Mapping
 - Mux , DeMux < Encoder & Decoder
 - Organisation of main memory
 - CISC
 - Counters
 - Cache Coherence
 - RAMs - SRAM , DRAM
 - Amdahl Law
 - Pipelining
 - Parallelism
 - Addressing modes
 - Multilevel Viewpoint of machine