introduction of computer-system architecture
Computer-System Architecture
How a Modern Computer Works
- DMA（Direct Memory Access)直接記憶體存取
能夠減少CPU cycle，減少CPU介入
讓硬體直接跟記憶體溝通的技術
Multiprocessors systems (parallel systems, tightly-coupled systems)
優點 :
- Speed up - Increased throughput
- Cost down - Economy of scale
- Increased reliability – graceful degradation
壞掉不會一次壞全部，比如很多顆CPU壞其中一顆傷害就還好
fault tolerance system 容錯系統
Two types :
- Symmetric Multiprocessing > SMP (對稱)
- Asymmetric Multiprocessing > ASMP or AMP
SMP :
• Each processor perform all tasks within OS
• Advantage
• Increased reliability
• Efficient
• Disadvantage
• Design complexity
• Mutually exclusive resource 互斥資源
ASMP :
• A less expensive options than SMP
• More common in extremely large systems
• Not all processors are treated equally
• Master processor schedules and allocates work to
slave(奴隸) processors : "a master- slave relationship"
• Bottleneck(瓶頸) : Master processor
The modern computer :
1.Hyperthreading Processors超線程處理器
2.Multiple Cores over a Single Chip (多核心在同一晶片)
Loosely-Coupled Systems :
Processors do not share memory or a clock
基本架構:
1.各processor有自己的clock及menory
2.通常各processor會有自己的作業系統
3.各processor之間的溝通方式大多用高速匯流排或message passing
例子:Blade Servers刀鋒伺服器