Memory and Storage

Memory and Storage

1. Primary

   • RAM - Random Access Memory
     • Volatile - Needs power to retain data.
     • Has a certain limit - less than secondary storage.
       • However, a lot faster than secondary storage, as closer to CPU.
         • Slower than cache, but more capacity.
     • Stores data currently being used, copies from secondary storage. When full, copies to virtual memory.
   • ROM - Read Only Memory
     • Tells CPU how to boot up, uses BIOS.
       • BIOS - Basic Input Output System
         • BIOS performs self checks Tests Memory See what Hardware is Present Copies Operating System into RAM.
     • Non Volatile - Maintains data when power is lost.
       • If volatile, computer would not know how to boot up.

2. Secondary

   • Long term storage
     • E.g. Hard Disk Drive, Solid State Drive, Magnetic Tape
       • HDD is made up of a stack of magnetised metal disks spinning between 5400 and 15000 rpm.
       • Solid State Drives have no moving parts. Most use a flash memory. SSDs have significantly faster read/write times than HDDs. Less storage than HDD.
       • Hybrid Drives exist which use SSD for storage, and a hard disk for data.
       • An optical disk is something like a CD(700MB), DVD(4.7GB) and Blurays(25GB).
   • Things to Consider include capacity, speed, portability, durability and reliability.

3. Tertiary Storage is used for long term purposes, such as archives and backups.

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