1. Am I RAM
Or am I ROM?

2. I contain the operating System, programs and data that is Being used.
An average laptop
Has around 4GB of me
My content changes
all the time
I contain the boot program
I’m small. Only
around 1 or 2 MB
I’m non-volatile
I’m read-only
I’m volatile

3. Lesson Objectives explain the need for virtual memory
describe cache memory
describe flash memory

4. HP Desktop Computer
6MB Cache
8GB RAM
£500

5. Cache Memory
Cache memory is memory that is located on the processor itself and is used to make the computer faster.
The cache memory acts as a buffer between the CPU and the RAM.

6. Cache Memory CPU Cache RAM The CPU request data
If the data is not in the Cache It requests the data from the RAM
CPU
Cache
RAM
Data copied to the Cache
Data sent to CPU
If the CPU then requests the same piece of data again, it will already be stored in the cache. This makes the process quicker as it does not have to go to the RAM

7. The transfer between the cache memory and the main processor is much faster than the transfer between the RAM and the cache memory.
When the processor tries to fetch the data again, it first checks whether the data is already in the cache memory. If it is, then the data is fetched from the cache memory and not from the RAM. This way, by storing the data that is fetched most often so that it does not need to be fetched from the RAM, the cache memory makes the whole system a lot faster.
The larger the cache memory, the more the improvement in performance will be. For this reason, modern processors include up to 8 MB or more of cache memory.

8. Why don’t we always use the cache for everything?
Because it’s much more expensive.
This is why you often have a small cache compared to the amount of RAM

9. Running out of RAM?
Have you ever been using a computer and the message “You are low on virtual memory, please close some applications”?

10. When there is not enough RAM to deal with all the demands on the computer it will use a section of the hard disk as a temporary store. This is called VIRTUAL MEMORY.
Total memory in use
Hard disk
RAM

11. Virtual Memory
The computer can take some programs out of the RAM and store them in a reserved part of the hard drive which frees up some RAM that can be now be used to open more programs.
When any of the programs that have been transferred to the hard disk are needed again, they need to be transferred back into the RAM before they can be used

12. Virtual Memory Virtual memory is not a permanent solution.
The time taken to access the hard disk on a computer is significantly longer than that required to access RAM.
If a computer is having to move data between the hard disk and RAM constantly, it will slow down the computer significantly

13. Task 1:
Using Publisher or Word, create an A4 revision poster about the topic of Memory. You must include
RAM
ROM
Cache
Virtual
You may use the internet for research and images.

14. Key Words Processor Random Access Memory Read Only Memory CPU Data
Volatile
Permanent

15. MEMORY ROM RAM Virtual Cache Holds the boot up programs
Runs as soon as the computer is turned on
Is non volatile, so it won’t be lost when there is no power
Usually quite small in capacity
RAM
Holds data on the programs that are running
Is volatile, so it is lost when the power is turned off
4GB standard for laptops
The more RAM the better the performance
MEMORY
Virtual
Used when running out of RAM
Uses a section of the harddrive to temporarily store data on programs
Takes longer than accessing RAM, so not a permanent solution
Cache
Located on the processor
Small compared to RAM
Much quicker than RAM but much more expensive
Used to hold data that is used a lot