add(cs24): add chapter 1 notes

university/cs24-introduction-to-computer-systems/010-a-tour-of-computer-systems.mdx

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+---
+sidebar_label: A Tour of Computer Systems
+description: A computer systems consists of hardware and systems software that work together to run application programs.
+---
+
+# A Tour of Computer Systems
+
+## Hardware Organization of a System
+
+![Hardwares](_assets-01/fig-1.4.png)
+
+### Buses
+
+Running throughout the system is a collection of electrical conduits called **buses** that carrary bytes of information back and forth between components.
+
+**Buses** are designed to transfer fixed-size chunks of bytes known as **words**. The number of bytes in a word (the _word size_) is a fundamental system parameter that varies across systems.
+
+:::info
+
+_word size_ determines the size of the data units that can be processed by the processor.
+
+Word size is a fundamental concept in CPU architecture, and it refers to the number of bits that a CPU can process and manipulate as a single unit. It determines the size of the following:
+
+- Processor registers
+- Memory addresses
+- Instruction operands
+- Data types (e.g., integers, floating-point numbers)
+- Internal data paths (e.g., ALU, load/store unit)
+
+Common word sizes for CPU architectures include:
+
+- 8-bit (e.g., Intel 8080)
+- 16-bit (e.g., Intel 8086)
+- 32-bit (e.g., Intel 80386)
+- 64-bit (e.g., AMD Opteron, Intel Core i7)
+
+:::
+
+### I/O Devices
+
+Input/Output devices are the system's connection to the external world.
+
+Each I/O device is connected to the I/O bus by either a _controller_ or _adapter_. The purpose of _controller_ and _adapter_ is to transfer information between the I/O bus and an I/O device.
+
+### Main Memory
+
+**Main Memory** also known as **Random Access Memory (RAM)** is a temporary storage device that holds data and applications while a computer is running.
+
+:::caution
+
+It is a **volatile** memory techonology, meaning that its contents are lost when the computer is powered off.
+
+:::
+
+### Processor
+
+The _central processing unit_ (CPU) is the engine that interprets (or _executes_) instructions stored in [main memory](#main-memory).
+
+#### Program Counter
+
+The core of a CPU is a word-sized storage device (or _register_) called _program counter_ (PC). It contains the memory address of the next instruction to be executed. The **PC** is incremented each an instruction is fetched, so it always points to the address of the next instruction in memory.
+
+#### Register
+
+Is a small amount of storage that is easily accessible to the processor. It is used to hold data and instructions temporarily.
+
+## Caches
+
+A system spends a lot of time moving information from one place to another.
+
+To improve the performance, system designers include smaller faster storage devices called _cache memories_ that serve as temporary staging areas for information that the processor is likely to need in the near future.
+
+The **L1** and **L2** caches are implemented with a hardware techonology known as _static random access memory_ (SRAM).
+
+## Storage Devices From a Hierarchy
+
+![Memory Hierarchy](_assets-01/fig-1.9.png)
+
+The main idea of a memory hierarchy is that storage at one level serves as a cache for storage at the next lower level.
+
+- The register file is a cache for the L1 cache.
+- Caches L1 and L2 are caches for L2 and L3 respectively.
+- The L3 cache is a cache for the main memory, which is a cache for the disk.
+- The local disk serves as a cache for data stored on the disks of other systems. (S3 buckets)

university/cs24-introduction-to-computer-systems/_category_.json

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+{
+  "label": "Introduction to Computer Systems",
+  "position": 6
+}