Virtual Memory

• RAM is faster than the hard disk because:

  • The RAM has no moving parts
  • The hard disk has a drive head that is a mechanical component
  • The RAM is physically closer to the CPU connected on the Northbridge
  • The hard disk is further away from the CPU connected on the Southbridge
• Virtual Memory:

  • When the RAM is full, a proportion of secondary storage (often the hard disk) is used as an overflow allowing programs to continue to function, albeit slower
  • Virtual memory is actually hard-drive space which acts as RAM, but operates a lot more slowly than RAM
• RAM:

  • Random Access Memory (RAM) is where programs are loaded when the user opens them
  • It is a volatile memory device
• ROM:

  • Read Only Memory (ROM) stores the boot up scripts
  • It is a non-volatile memory device
• Cache Memory:

  • Cache is a few Mb of memory that sits inside the CPU
  • Data access speed in cache is equal to the CPU's speed, maintaining CPU performance
• How the amount of RAM affects performance:

  • Smaller amount of RAM leads to limited multitasking and greater need to use slower virtual memory
  • Larger amount of RAM leads to greater storage of programs/data, resulting in faster performance and effective multitasking
• When RAM gets too full, the operating system will mark out sections of the hard disk to temporarily store excess data. These sections are called virtual memory. Virtual memory is main memory because it is being accessed directly by the CPU, and it is volatile because the CPU will lose track of what data is stored where if it loses power