Fundamental quantitative principles of computer design and modern techniques for performance enhancement are covered. Role of technology and factors affecting the cost of computer systems are addressed. Instruction set principles are reviewed. RISC-V architecture is examined as a case study. Memory hierarchy in computer systems is examined. Principles of cache and virtual memory are introduced. Instruction-level parallelism and pipelining concepts are explained. Design approaches to exploit data-level parallelism are introduced. Vector, SIMD, and GPU architectures are examined. Multiprocessors that achieve higher performance by simultaneously executing multiple instruction streams on different processors are explained. Design guidelines for domain-specific architectures for enhanced performance and energy-efficiency in computer systems are introduced.