1.2 - Memory

1.2 - Memory

1. RAM

   • Random Access Memory
   • There are lots of different RAMs:
     • DRAM (Dynamic Random-Access Memory)
     • SDRAM (Synchronous Dynamic Random-Access Memory)
     • FPM RAM
     • EDO RAM
     • DDR (SD)RAM (Double Data Rate (Synchronous Dynamic) Random-Access Memory)
   • RAM is used to store the instructions that are used by the CPU
   • RAM is known as volatile memory, which means it forgets everything as soon as the power is switched off
   • The computer can not work without RAM because the operating system and programs need RAM to work, and the lack of RAM would be detected by the BIOS and the computer would fail the POST.

2. ROM

   • Read-Only Memory
   • ROM is non-volatile, which means it remembers its data, even after the power is switched off
   • ROM Chips
     • They store the BIOS on a computer.
       • BIOS stands for Basic Input Output System. This tells the computer what it should do when it is first turned on.
       • BIOS also lets you change the boot order for the PC. When it is first powered up the BIOS does a POST
         • POST stands for Power-On Self Test.
           • When the computer boots up, it checks all the components attached to it to check none of them have a fault If the POST fails, the motherboard beeps.
     • You can’t save to ROM chips

3. Virtual Memory

   • Virtual memory is a portion of the hard drive that is used as an “overflow” for when there is too much data for the RAM to hold at once Virtual memory is significantly slower than RAM because it is on the hard drive, which takes much longer for the CPU to access Adding more RAM speeds up your computer because it means more instructions can be stored in the RAM, making them quicker to fetch and execute. In order to access something in the virtual memory, it has to be moved into the RAM, which means moving something else out, then moving it in then running it. You can tell how much virtual memory is currently in use (on Windows) by using: Resource Monitor The Resource Monitor will tell you exactly how much RAM is being used, what is using it, and allow you to sort the list of apps using it by several different categories. However, it doesn’t offer much else. You can reduce the computer’s need to use virtual memory by getting bigger RAM. A flash drive can be used to support the RAM.

4. Flash Memory

   • You can run some programs from flash memory, but since it is attached to the Operating System, it will only be runnable on that device.
   • Flash memory is a form of non-volatile storage.
   • Flash memory is very cheap and is found in many forms, including: USB sticks SD cards Micro SD cards
   • Flash memory stores data on small chips
   • Each bit of data is stored in a tiny circuit (the memory cell) consisting of transistors.