Hardware Flashcards
What is an address bus
A one way connection between the main memory and cpu, it carries the address of the next instruction that the cpu sends to the main memory
What is a data bus
A two way connection between the cpu and main memory and secondary storage. It carries the instruction at the address the cpu sent on the address bus. It is two way as the processor may have to send data back.
What is a control bus
A connection that carries signals to show if the data bus and address bus is in use
What does the random access in ram mean
Not actually random but it means you can write anywhere in that memory space at any time. You don’t have to put the next thing straight after the last one like you have to with magnetic tape
What is ram for
To load programs onto from the hard drive so the cpu can access the instructions
What is virtual memory
Memory from the hard drive that acts like ram if there isn’t enough ram. It’s slower than ram so isn’t ideal and the instructions the cpu needs still have to be in the ram so data is always swapping places from the ram and the virtual memory. This can make it very slow
What does it mean to be volatile
If the memory is volatile, once it no longer has power, the data stored will be removed
Properties of ram
Very fast, not as fast as cache
Expensive per gB
Volatile
Can be read and written
Properties of rom
Non volatile
Can’t be written on
Read only
What is the bootstrap loader
A small program in the rom that when the computer is first turned on, it runs and loads the operating system. Once the os is loaded, it takes over the rest. Like the apu of a plane starting up the engines. Bootstrap has been abbreviated to booting, boot up a computer
Examples of primary and secondary memory
Ram
Hard drive, memory sticks, tapes, CDs. These are all long term, non volatile storage types
What are the important things about secondary storage when choosing one to buy
Has to have a large capacity
Doesn’t have to be super fast as that will make it expensive
How easy is it carry, is it permanent like hard drives or is it portable like memory sticks
How durable is it, will it survive being dropped
How reliable is it, will it last years or a few weeks
How do optical storage media work
Coated in a dye layer on the disk, a laser can change the dye so its opaque or transparent
Laser shone onto disk and it’s reflected if transparent or it gets absorbed if it’s opaque
If reflection detected, this is 0 and 1 is when it’s not reflected.
Benefits of solid state storage
No moving parts so more reliable and faster
How does solid state memory work
Basically a big grid of transistors ( switches) that can be switched and kept into one persition. Each transistor can store one bit of data, 1 or 0. This is called EEPROM, electronically erasable programmable read only memory
