Objectives

Notes

• This is section 1.2.2 of the book.
• Memory is a hierarchy
  • Registers
  • [cache], but this is mostly out of reach for programmers
  • [ROM], mostly holds the boot loader
  • RAM
  • Secondary Storage
  • Removable Media/Network Storage
• ROM
  • Holds the boot loader
  • BIOS/UEFI
  • Basic Input Output System
  • Unified Extensible Firmware Interface
  • Contains the instructions to get a machine started
    • Elementary display
    • Elementary media access
  • GPT is the GUID Partition Table
    • A table that describes how data is laid out on a hard drive.
    • UEFI supports this, so it can access data stored on media.
    • Old world Master Boot Record
  • 
• Cache
  • AFIK this is completely or nearly completely managed by the hardware
  • It does it's job but is not really accessible by the programmer.
  • But thank the inventor for this code.
• RAM
  • Volatile
  • Comparatively Small, usually insufficient, the OS needs to help here.
  • Shared, the OS needs to help here too.
  • Used to store program and data
  • Memory is an array of bytes (8 bits)
  • Moved to and from CPU/cores with load and store instructions
  • (Fetch - Decode - Execute)
• I/O
  • This is a major task, as IO is so much slower than the CPU
  • Figure 1.7 in the book provides an overview of this process
  • DMA - Direct Memory Access
    • Devices can write directly to main memory without the CPU
  • To do I/O
    • CPU starts transaction
    • Device is given instructions to perform whatever
    • Device reads/writes directly to memory
    • When the device is done, an interrupt is issued
    • CPU deals with the data.