Reading Journal Week 3 Memory - echadbourne/ChadbourneSYS-140 GitHub Wiki

All information and images are from Chapter 6 of the textbook (except my response), if they are from somewhere else the source will be cited

Memory Overview

The two main types of memory that a computer uses are random access memory (RAM) and read-only memory (ROM). RAM is volatile (goes away when power is turned off), is found on the motherboard of the computer, stores part of the running Operating System, and holds the applications that are actively running on the computer. In comparison, ROM is non volatile. In addition, RAM can be changed while ROM cannot. The image below (from the textbook) outlines the differences in RAM and ROM. The two types of RAM are dynamic RAM (DRAM) and static RAM (SRAM). DRAM is slower because the data needs to be refreshed periodically, (through a process called “refresh”) and DRAM is what most of the RAM on the motherboard is. SRAM can also be called “cache memory,” and is essentially used as a place to store information that the computer needs right away, since it is the fastest memory.

My Response:

The information in this section is important because one needs to understand how memory works in a computer to know how to make it as efficient as possible when building a computer. In addition, knowing how memory works in conjunction with the rest of the motherboard is important for diagnosing potential problems with a device.

Memory Module Types

This section is about the different types of DRAM available for computers. The memory chips that a computer can support is determined by the chipset that it has, as the chipset controls the “...local bus, memory, DMA, interrupts, and cache memory” (paragraph 2 of section “Planning Memory Installation - Memory Module Types”). The different types of DRAM are SDRAM, DDR, DDR2, DDR3, DDR3L, DDR4, DDR4L, and Rambus DRAM. The differences between each type are outlined in the table below:

My Response:

Aside from their physical differences, and the fact that some are just better than others, I don’t totally understand the differences between the various DRAM types. The differences are only sort of explained, so I would love to know the practical differences in DRAM types and what different types are good for.
I had a hard time understanding this section because of all of the acronyms for everything, it was hard to keep track. I hope that when we go over this in class it will all make more sense.

Memory Features

This module was about the various features that come with memory modules. There are a number of error correcting features, like parity or error correcting code (ECC), that can come with a memory module, in addition to buffered and unbuffered memory, serial presence detect (SPD), single and dual sided styles, deal voltage memory, and extreme memory profile (XMP). Regarding what motherboards can support for features, the textbook states: “Keep in mind that some motherboards might support both non-parity and ECC (error correcting code) or might require a certain feature such as SPD.” Memory modules can also use more than one category of features. The definitions of the features are listed in the tables from the textbook below for reference

My Response:

Understanding that there are different features for memory makes sense to me. Some of the features seemed to be pretty straightforward, like how parity works. Initially, I didn’t understand why buffered memory was used in higher end computers instead of unbuffered memory, however upon reading through the tables again that makes more sense. I believe that is because buffered memory is more accurate.

Windows Disk Caching

This section was mostly about virtual memory and swap files. Virtual memory is a method of using hard drive space as RAM for applications. It is dynamic, and changes based on the demand from applications, which can be altered based on application size and how many applications are in use. A swap file is the chunk of the hard drive that is used by applications as RAM, and can be altered manually. It is best to allocate a large chunk of hard disk space to the swap file. When an application is in use a section of virtual memory is allocated to it??? I don’t understand the rest of this. I did my best to explain what I do understand though.

My Response:

The definitions of virtual memory and swap files makes sense to me, but from here I don’t understand how this works. I think I would almost have to “see” this in action, or have it explained step-by-step for a better understanding of how this works in actuality.

Monitoring Memory Usage in Windows

This section contains the instructions for bringing up and looking at the memory usage in Windows 7, 8, and 10. In either of the “Task Manager” applications (different between 7 and 8 or 10) you would look at the performance tab to view the memory usage. The table below shows what each of the numbers mean in the Windows 10 task manager.

My Response:

We used the Windows 10 Task Manager just the other day in a lab, so I’ve seen how to do it before. We did not specifically look at the “memory” tab in the application, so I decided to record the table of what each thing means for future reference. I don’t totally understand the “paged” thing, but I am hoping that when we go over it in class (since this is also related to the section before that I don’t understand) it will make more sense.

Flash Memory

Flash Memory is a type of memory that can hold data when the computer is off - it does not need power thus it is nonvolatile. Examples of flash memory include flash drives and SD cards. Uses for flash memory include: “PCs use flash memory as a replacement for the BIOS chip. Network devices, smartphones, and tablets use flash memory to store the operating system and instructions. Some tablets can use external flash media for storage. Digital cameras use flash memory to store pictures; scanners use flash memory to store images; printers use flash memory to store fonts.” (Schmidt, Flash Memory Section, Paragraph 1)

My Response:

There was nothing new to me in this section, I have used flash drives and SD cards before so I know the basics of how they work. I did want to record the different uses for flash memory though because I figured it might be useful in the future.