Unit 1.2 Memory

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Unit 1.2 Mind map
Mathew Wheatley
Mind Map by Mathew Wheatley, updated more than 1 year ago
Mathew Wheatley
Created by Mathew Wheatley over 6 years ago
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Resource summary

Unit 1.2 Memory
  1. ROM
    1. Non Volatile form of memory
      1. Retains its information through power off
        1. Contains data that is pre-written and permanently written on a ROM chip
          1. The location of the POST sequence
            1. Power On Self- Test
              1. BIOS chip performs checks
                1. Makes sure components are present and fuctional
                  1. Once completed successfully, the OS boots up
                  2. Uses the BIOS instructions
                    1. Basic Input Output System
                  3. Considered as permanent
                    1. Read-Only Memory
                    2. RAM
                      1. A volatile form of memory
                        1. Loses its information at power off
                          1. Contains the data and programs currently in use
                            1. Can be DRAM or SRAM
                              1. DRAM - Dynamic RAM
                                1. Slower as needs to be refreshed thousands of times per second
                                  1. Cheaper and so more common
                                  2. SRAM - Static RAM
                                    1. Faster as doesnt need to refresh
                                      1. Expensive and Less Common
                                    2. Random Access Memory
                                    3. Flash Memory
                                      1. Can be easily broken
                                        1. Relatively Cheap
                                          1. Examples include USB drives and Memory Cards
                                            1. Can very easily be broken and/or stolen
                                              1. Can be used to back up computational data
                                              2. Virtual Memory
                                                1. A simulated form of memory found on the hard drive
                                                  1. Created by the Operating System (OS)
                                                    1. It is needed to make more memory than is actually in the system
                                                      1. Creates the virtual memory manager
                                                        1. Which then creates a file on the hard drive
                                                          1. Now the OS can address the memory
                                                        2. It's needed when you need to run things that RAM can't support.
                                                        3. Solid State Media
                                                          1. Contains no moving parts
                                                            1. Uses Flash Memory
                                                            2. Registers within a computer
                                                              1. See my Unit 1.1 Revision Map
                                                                1. There are multiple forms of register
                                                                2. Disc Thrashing - The process the system uses to move data between Virtual Memory, RAM and Cache.
                                                                  1. Depends on the frequency of the data, how often it's used.
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