Computer: CPU, Hard Disk, and RAM Most people will purchase at least one compute
ID: 3691970 • Letter: C
Question
Computer: CPU, Hard Disk, and RAM
Most people will purchase at least one computer in their lifetime. Making that decision is a difficult one as there are so many options available from which to choose. One of the most important aspects of the computer’s hardware is the CPU, but CPU is often confused with hard disk space and RAM.
Write a short paper that discusses the differences between these three concepts and how to use this information to make purchase decisions. Make suggestions to a fellow college student about the right amount of memory for a laptop computer. How do they go about selecting the proper type and amount of RAM for a laptop? Also, research and include in the paper the top five computer memory upgrades.
Suggested Websites
http://askleo.com/whats_the_difference_between_memory_and_hard_disk_space/
http://www.memorybenchmark.net/
http://www.crucial.com/
http://computer-memory-upgrade-review.toptenreviews.com/
http://www.wikihow.com/Choose-a-Computer
Suggested Keywords
soc chips, mobile device soc, what are soc chips, who is using soc chips
Explanation / Answer
Answer for Question:
This is what is called the memory hierarchy. The general idea is that memory per unit of capacity gets more and more expensive with increasing speed of access.
The fastest memory available to the processor are registers in the CPU. Depending on the architecture you have only 10s of them, each capable of holding generally 4 or 8 bytes. But data in registers can be accessed instantaneously, as its located right inside the CPU, and all computation is actually done on data in the registers. If the data required is not present there, it is fetched.
From where?
It goes down one step in the hierarchy, the CPU cache(s). If the data is found in the cache (called a cache hit), it fetches the data from the cache. Modern processors have several caches, the L1 being the smallest and fastest with L3 being about a few MBs in size with access times about 100x slower than L1.
If the data is not found in the cache, it is fetched from RAM. RAM is slower than even the slowest CPU cache, but it has much much more capacity (commonly 4GB to 16, or 32 or even 64 GB in commodity PCs).
Upto this point in the memory hierarchy, the memory is volatile, meaning that if you switch off your computer you lose all the data. To permanently store your data, you need access to some kind of storage.
This is an important distinction to make, because in common parlance, hard disk is not memory, even though its still characterized by its capacity in MB or GB. Accessing disk takes milliseconds compared to the nanoseconds of caches or RAM, and with just disk computing would be unusably slow. The CPU will be sitting there idle for tens of thousands of CPU cycles waiting for data. That is why we need RAM and caches to speed things up.
On the other hand, memory has the disadvantage of being much more expensive than disks and also losing its contents on switch off. Things nowadays have improved somewhat with the advent of SSDs, which again fit nicely in the memory hierarchy between RAM and disk and is essentially used by most people as a cache for the disk.
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