Week 3 - Computer Memory

Image source:  https://upload.wikimedia.org/wikipedia/commons/thumb/2/2c/Samsung-1GB-DDR2-Laptop-RAM.jpg/1280px-Samsung-1GB-DDR2-Laptop-RAM.jpg

There are primarily 3 types of memory:

• RAM (Random Access Memory) - primary memory where data is stored
• ROM (Read Only Memory) - primary memory where data is permanently stored
• Flash memory - secondary memory that is used to store data to be used later or on the go

RAM is very volatile and will not be stored when the power is turned off.  It allows more than one program to be running all at once in order for the motherboard to activate what it needs to do.  It takes the stress off of the CPU and allows the user to switch to different programs smoothly, allowing the computer to do more things at once.  There are Many types like DDR, DDR2, DDR3, DDR4, DDR3L, SODDIM, as a few more. The Frequency can range from 1000 to over 3600 mhz.

ROM is the permanent memory where the CPU gets the program to run.  This can also be used in small devices that need to run a program as soon as they are started up and tells the item what it needs to do.  ROM is available in several different types, including PROM, EPROM, and EEPROM.

• PROM - stands for Programmable Read-Only Memory, and it is different from true ROM in that while a ROM is programmed (i.e. has data written to it) during the manufacturing process, a PROM is manufactured in an empty state and then programmed later using a PROM programmer or burner.

• EPROM - stands for Erasable Programmable Read-Only Memory, and as the name suggests, data stored in an EPROM can be erased and the EPROM reprogrammed. Erasing an EPROM involves removing it from the computer and exposing it to ultraviolet light before re-burning it.

• EEPROM - stands for Electrically Erasable Programmable Read-Only Memory, and the distinction between EPROM and EEPROM is that the latter can be erased and written to by the computer system it is installed in. In that sense EEPROM is not strictly read-only. However in many cases the write process is slow, so it is normally only done to update program code such as firmware or BIOS code on an occasional basis

Secondary memory is the memory that comes from the hard drive, Solid State drives (SSD), and optical (CD or DVD drives).  This includes stick drives and detachable hard drives, and possibly cloud storage. 

References

Noor, M. (2018, June 8). What is computer memory? What are different types of computer memory? Retrieved from Quora: https://www.quora.com/What-is-computer-memory-What-are-different-types-of-computer-memory

Rubens, P. (2019, May 17). Types of Computer Memory. Retrieved from Enterprise Forum: https://www.enterprisestorageforum.com/storage-hardware/types-of-computer-memory.html