CPU and Memory

CPU and Memory

1. CPU performance

   • Cores
     • Cores contain a ALU, Control Unit and Registers
     • A core is a processing unit inside the CPU
   • Clock Speed
     • Indicates how fast the CPU can run
     • Clock speed can be changed in the BIOS
     • If the clock speed is increased too much the CPU may not be able to keep up causing data to become corrupt
   • Cache
     • Level 1 Cache
       • Usually part of the CPU chip itself
       • Smallest and the fastest to access
     • Level 2 & 3 Cache
       • Built between the CPU and the RAM
       • L2 and L3 are slower to access than L1
       • The more L2 and L3 memory available the faster the computer will run

2. Processor type

   • CISC
     • Complex instruction set computing
     • Most desktop and Laptop computers use CISC
   • RISC
     • Reduced information set computing
     • Most smartphones and tablets use RISC
   • CISC and RISC comparison
     • CISC CPUs are bigger then RISC
     • RISC CPU's run at a lower clock speed than CISC
     • CISC CPU's use more electricity
     • RISC CPU's use less power and are cheaper to make

3. Motherboard is a circuit board that connects the CPU to the memory and all the other hardware

4. Buses

   • Address Bus
     • This sends information about where the data needs to go by sending an address to the memory
     • The address bus only sends data in one direction from the CPU to RAM,
   • Data Bus
     • This sends data to the memory or receives data from the memory
     • Data can flow both ways
   • Buses are circuits on the motherboard that connect the CPU to the other components

5. Bridges

   • Bridges manage how data and instructions are transferred between the memory,CPU and other devices
   • Northbridge
     • Northbridge connects the CPU,RAM and GPU through the Front Side Bus
   • Southbridge
     • Southbridge connects to the Northbridge.All the other hardware connects to the CPU through the Southbridge

6. Memory

   • Memory is the area where the computer stores or remembers data
   • Primary Memory
     • Closest to the CPU: Registers,Cache,RAM,Virtual Memory
   • Latency is the time it takes for components to respond to a request
   • RAM
     • RAM is the main place for storing instructions and data while the program is being executed
   • Word size
     • The word size of the machine is how many bits the CPU can manipulate in one go
     • Increasing the word size means more data can be manipulated at a greater speed

7. DRAM and SRAM

   • Dynamic RAM
     • Uses a capacitor and a transistor to represent and store a bit of data.
     • DRAM is used for the main RAM memory
   • Static RAM
     • Uses a group of transistors combined for each bit of data
     • Used for cache memory
     • More complex to build so more expensive than DRAM
     • SRAM is much faster than DRAM

8. Virtual Memory

   • Virtual memory is a section of volatile memory created temporarily on the storage drive
   • Virtual Memory is much slower than main memory
   • Swapping is the process the OS uses to move data between RAM and Virtual memory

9. ROM

   • EEPROM
     • Electrically Eraseable Read Only Memory
     • Used in Pc's and smartphones as firmware can easily updated by owner
   • PROM
     • Programmable Read Only Memory
     • PROM chips can be brought cheaply and programmed directly by programmer
   • Read Only Memory is a flash memory chip
   • It contains Non Volatile memory, which means that the contents cannot be changed and keeps its memory when the computer is turned off
   • ROM contains the BIOS which is in the firmware for the motherboard
   • The BIOS contains the bootstrap which takes the computer through the steps to load the operating system
   • POST is the process where the computer beeps to say it is starting to load the Operating system