System Architecture (1.1)

(Central Processing Unit) is the hardware component responsible for processing and executing all the instructions inside of a computer. - The speed is measured in Hz, so a 2Ghz CPU would process 2 billion instructions/CPU cycles per second

• The higher the clock speed, the faster the rate at which the CPU can execute instructions per second

• More cores results in instructions being executed in parallel per core , resulting in faster execution

• A larger cache size means the CPU can access more temporary stored data which is much faster than if stored in RAM

• a computer system built into another device. These are dedicated systems produced to be efficient at carrying out its specific task. • They tend to contain more ROM than RAM, as they are specialised to carry out limited functions (cheaper to design and build)

• Washing machine, • MP3 player, • Dishwasher • smartwatch

• Control unit (Directs the instructions within the processor) • Arithmetic & Logic Unit (ALU) (Responsible for any arithmetic and logic calculations in the processor) • Cache (Stores the most frequently accessed instructions from the RAM (faster than RAM, but holds much less data)) • Registers (Small amounts of highspeed memory located within the CPU)

• Memory address register (MAR) (Holds memory addresses about to be used by the CPU) • Memory Data Register (MDR) (Holds the actual data or instruction to be used by CPU) • Accumulator (Stores intermediate results of calculations in the ALU) • Program Counter (PC) (Holds the memory address of the instruction for each cycle)

• copy memory address from program counter to the MAR, and copy instruction from the MAR address to the MDR. Increase the program counter to point to next instruction.

• instruction in MDR is decoded by the CU

• the instruction is performed/executed. This could be load data/write data to or from memory, or do a calculation or logic operation (using ALU).

• The ROM is an internal hardware component which is part of the computers main memory • ROM is non-volatile memory which means the data is saved/kept by the computer when the power turns off. • ROM is used to store the BIOS (basic input output system) ʹ instructions needed to turn the computer on or the “bootup” sequence (bootloader)

• The RAM is another internal hardware component which is part of the computer’s main memory • RAM is used to store any running applications while the computer is ON • The RAM is volatile memory meaning the data in the RAM is deleted/erased when the power turns off

• A computer needs both RAM and ROM to function correctly. However, the ROM in a computer is difficult to upgrade or change, whereas the RAM can be easily upgraded and changed to hold more data • RAM holds a lot more data than the ROM • Typical RAM is 4GB and typical ROM is 4MB.

• Virtual memory is memory which the computer uses by allocating a section of secondary storage to store running applications. This is only used when the RAM in a computer is full and runs out of capacity.

• CPU move data from RAM into the secondary storage, known as a “paging file”, so the CPU can continue with its execution of instructions from RAM. This is copied back into the RAM when it is needed

• The virtual memory is slower than the RAM but allows the computer to continue functioning by using part of the HDD or SSD to store some data from the RAM.

• Flash memory is non-volatile memory which is used to store data and transfer this between a computer and another device. Flash memory can have its contents edited and changed according to the user’s needs, and it can also be electronically programmed

• USB drives • SD cards • Solid State Drives (SSDs)

• Secondary storage is needed to save data and programs that are needed after the computer is turned off. It is a form of non-volatile memory. • Secondary storage can hold much greater capacity of memory than main memory, but is slower to access as it is not directly accessible by the CPU.

• Capacity (how much data can be stored) • Speed (how fast the data can be read/written) • Portability (is the device easy to move around and take with you) • Durability (how will it be affected by drops, shocks, water etc) • Reliability (chances of data always loading correctly) • Cost (how much is the cost per GB)

• a type of secondary storage which is typically found in Hard Disk Drives (HDDs). • Data is stored using magnetic dots which have a magnetic polarisation, on areas of the disk called sectors which are found within circular tracks. • The data will have a positive or negative polarity, which is read by the read/write head on a moving arm.

Advantages: largest storage capacity, cheaper to produce than solid state drives Disadvantages: more likely to be damaged by dropping due to moving parts, not as fast to read/write data as a solid state drive

• Optical memory is a type of secondary storage which uses lasers to read and write data. • Examples of optical memory include CDs, DVDs and Blu-ray disks. • Data can be read by using a laser which reads a series of pits and lands. • The laser is shone onto the disk surface which is reflected, and this represents 0s and 1s.