Lecture 2 Flashcards
What is a microprocessor?
It is a processor that is built from a large amount of IC’s and is packaged onto a single IC chip.
What is a microcomputer?
A minor computer that uses a microprocessor. It will have memory and other peripherals.
What is a micro controller?
It is a microcomputer that contains all of the peripherals along with the CPU on the one chip.
In the ALU, what is the function of the Opcode and Status inputs and outputs?
The opcode will tell the ALU what type of operation it is performing. The status output will tell the controller as to the state of the output.
What is the role of the command unit?
It is the commander of the CPU, it fetches instructions and decodes them to tell it what signals to send to other units.
What is the Program Counter?
It contains the address of the next instruction to be read from memory during the fetch cycle.
How does a CPU read instructions?
- Fetch the instruction from memory.
- Decode the instruction into code signals.
- Execute the instruction.
- Access and read any memory that is needed.
- Write back to memory if needed.
What is CPU pipelining?
It is the process of running multiple events at once. If we sequentially ran the process for the CPU to fetch instructions then it would take a long time because we would have to wait for it to finish writing to memory before we can fetch the next instruction. Pipelining will start fetching the next instruction along with working with the current one.
How is information stored in memory?
As words, and the length of the word will depend on the processor. The words will contain multiple bytes of 8 bits. Each word has a specific address in memory.
How many data lines connect the memory to the CPU?
3
What are the 3 data lines connecting memory to CPU?
- Address bus that determines the location of the memory to access.
- Data bus to carry data to or from the memory.
- Read / Write. Logic 1 on this line will mean read while a 0 means write.
What is the Van Neumann architecture?
It is a computer architecture that contains only one memory for instructions and data. This creates a performance bottleneck because it can’t read or write to the memory at the same time.
What is Harvard Architecture?
It is a more complex architecture that has seperate memory for both instructions and data. This means that read and write can occur at the same time.
What is the equation that governs how many items can be stored at an N bit memory address?
n = 2^k
Where K = log(n) / log base 2
How do we read memory?
- Issue a read command
2. Place the address of the word that we want to read on the address bus.
Why do we have to wait 1 access time before reading or writing to memory?
Because memory cannot respond instantly.
What is the condition to read from memory?
The reading process must be non destructive.
How do we write to memory?
- Place the address to be written to on memory.
2. Place the data to be written on the address bus.
What is the cycle time?
It is the time that the write command must be active to allow the memory to write.
Is writing memory destructive?
YES
What is RAM?
Random Access Memory.
What is Static Ram?
It is faster than dynamic RAM but this makes it more expensive. It does not require a refresh. Caches.
What is Dynamic RAM?
It is cheaper than Static RAM but it requires a constant refresh otherwise the data is gone.
What is ROM and what are its properties?
Read Only Memory.
It is non volatile and is programmed during manufacturing.
It has slower write speeds that are at fixed write cycles.
What is Masked ROM?
It is is programmed at manufacturing using an expensive mask to program the proper bit patterns. Something like photolithography etch that uses a laser.
Programmable ROM? (PROM)
ROM that to re program it we need high voltage to blow up the fuses.
What is Erasable PROM? (EPROM)
We use a special device called a PROM programmer to write to the ROM by over voltaging certain inputs. Can also use UV light.
Electrically EPROM?
The data can be erased and rewritten without removing them from their sockets.
What is the heirachy of memory?
We place the fastest memory closest to the processor.
What is locality of reference? (LOR)
It is the concept of accessing a value or related storage frequently.
What is temporal LOR?
It tells us whether memory locations in a programme are likely to be accessed again in a short period of time.
What is special LOR?
This is the concept that if we have already accessed one storage, what is the probability that we need to access another storage close to it.
What is the difference between memory mapped I/O and port mapped I/O?
Memory mapped will map I/O to the same memory address space as the program while Port will map it to a dedicated address space.
