1.2. 8 Great Ideas from Computer Science
- Moore’s law
- Abstraction
- Optimize for the Common Case
- Parallelism → thruput increase
- Pipelining → thuput increase
- Prediction
- Memory Hierarchy
- Redundancy
Abstraction: Application Software > Systems Software > Hardware.
Abstraction: High Level Language > Assembly Language > Binary Machine Language
Components of a Computer
Components of a Computer: Input/Output, Memory, Datapath, Control. Datapath & Control are sometimes combined as the CPU. Examples of I/O Devices: LCD displays (with frame buffers as pixels), touchscreens, etc.
Memory is built from DRAM (Dynamic Random Access Memory) (↔ Sequential random access memory, which is old technology). Memory Hierarchy: Main Memory (DRAM) > Secondary Memory (magnetic disks, flash memory).
Instruction Set Architecture (=architecture) is the information developers need to develop a proper binary machine language program, including I/O, memory layout, etc. ABI (Application Binary Interface) is the combination of the instruction set and the OS interface.
- Transistor: a electric switch
- VISI (Very Large-Scale Integrated Circuit): ICs with millions and billions of trasnsistors (Moore’s law predicts the geometric increase in the number of transistors per area.)
Manufacturing process of ICs
Silcon Ingot ⇒ Wafers ⇒ (processing steps) ⇒ Patterned Wafers ⇒ Diced Wafers (Dies) ⇒ Packaged Dies (patterned wafers, diced wafers and packaged wafers are each tested.)
- Defects can occur in each testing process. Yield measures the percentage of good dies from total # of dies on wafer.
- Cost of manufactoring, due to defects, is generally proportional to the square of each die area. Which means it’s impractical to design very big dies.
Parallelism
Improvement of response time fo CPUs began to slow around 2002. Since then cpu architects started to use multicore processors to augment performance. But since programmers had to rewrite programs for them it was hard to adopt—due to the overhead of communication & synchronization.
1.9. Real Stuff: Benchmarking the Intel Core I7
SPEC (System Performance Evaluation Cooperative) released standard benmarks for common programs. Types: integer benchmark / floating point benchmark. They give a score called a SPECratio per program which is calculated by: where reference time is from a reference processor and execution time is from the processor being benchmarked. The higher the better. Overall SPECratio of the CPU is a geometric mean of all programs’ SPECratios.
SPEC also released a SPECpower power consumption benchmark. It measures average power consumption and ssj_ops (server side Java operations per second), at load increments from 10%, 20%, …, 100%. The final number given is: