Memory Reading Journal

Memory Overview All computers need software in order to work. This software lives in the computer memory. There are two main types of memory, RAM and ROM. RAM is short for random access memory, it’s found on the motherboard. RAM can be changed, stores running applications and parts of the computer’s operating system, and is what is called Volatile Memory. Volatile memory means that when the computer is shut off all the data in the RAM is gone. ROM stands for read only memory. It cannot be changed, it’s found on adapters, and it’s nonvolatile. Nonvolatile means that the data stored in ROM is still there even when the computer is turned off. A hard disc is an example of ROM. There are two types of RAM, Dynamic RAM (DRAM) and Static RAM (SRAM). DRAM is less expensive but slower. In DRAM the 1’s and 0’s can leak out so they have to keep being rewritten in a process called refreshing. This process makes the DRAM slower. SRAM is the cache memory. It’s the fastest type of memory. This was interesting because sometimes it takes my brain a second to make connections. I made it through the entire section of reading and then when writing this reading journal I just realized that ROM was the hard disc. I was confused because I had only ever heard ROM be used in a CD-ROM context. It was just interesting to make that connection while reading. I also thought it was interesting because cache memory is described as a type of RAM memory in this section and I just hadn’t thought about the fact that it was considered RAM as well. I would recommend this reading because it helped me make some connections to some things I already knew from class. Planning A Memory Installation In this section I learned about memory module types and memory features. Some types of memory modules include Synchronous DRAM, Double Data Rate (DDR), DDR2, DDR3, DDR3L, DDR4, and DDR4L. Synchronous DRAM is a type of memory that allows fast burst access. It syncs up with the CPU clock signal so that it can quickly access the memory. Double Data Rate or DDR is a type of memory where data is transmitted on both the rising and falling sides of the clock signal so that it can be transmitted twice in that time period. DDR2 is another type of DDR but it isn’t compatible with DDR. DDR3 is an upgrade from DDR2, it works better for multi-core processors. DDR3L is a DDR3 that uses lower voltage, this means that it gets less hot and uses less power. DDR4 operates at a lower voltage than DDR3 and allows faster speeds. DDR4L uses less voltage than DDR4. I also learned that whether the motherboard is actually able to allow the faster memory chips depends on the chipset. I learned that to tell the difference between the chips you can look at the pins. DDR uses 184 pins, DDR2 and DDR3 use 240 pins, DDR4 has 288 pins. Even though they have the same number of pins DDR3 doesn’t fit in a DDR2 slot. Each of the modules also has a type of cooling system called a heat spreader on the outside. This is used to spread heat away from the memory. I also learned about memory features. Some of the features include parity, non-parity, error correcting code (ECC), unbuffered memory, buffered memory, single sided memory, double sided memory, and dual voltage memory. Parity is a method that checks how accurate the data is. Parity can detect if one bit is incorrect but not two. Non-parity is when chips don't check for errors. Error correcting code or ECC is an alternative to parity. It uses a mathematical algorithm to check accuracy. It can detect 4-bit memory errors and correct 1-bit memory errors. Unbuffered memory is the opposite of registered or buffered memory. It’s faster than buffered memory. Buffered Memory or registered memory have extra registers that delay all moves of data by one clock tick so accuracy can be checked. Single sided memory is a memory module that only has one “bank” of memory. Double sided memory is a single memory module that actually contains 2 banks of memory. It allows for more banks without taking up more space. Dual voltage memory is a module that works on lower voltage and therefore creates less heat. I thought this section was not super interesting. There seemed to be a couple important sections to note but everything else seemed like information that wasn’t relevant to us yet. I just had a hard time navigating through what was and wasn’t important. Windows Disk Caching In this section I learned that virtual memory is a method used where the computer uses hard drive space as if it were RAM. This allows the operating system to run large applications and use multiple applications. The amount of hard drive the computer uses changes depending on the amount it needs. That section that applications use as RAM is called a swap file. You want to put your swap file on the fastest hard drive and try to set aside as much space in your hard drive as possible. I also learned that In a 32 bit Windows system each process gets 4 Gb of space that's divided into 2 GB sections. The entire system shares 2 GB and the other 2GB section is for an application. That memory space is divided up into 4KB pages. This was interesting to me because I didn’t realize that you could use the hard disc/static memory as RAM. I have more questions as to how it works and how that affects the speed of the application. This does make sense to me because last year my hard drive was full and as a result I wasn’t able to use a lot of my applications, like Adobe photoshop, or illustrator. It wasn’t just saving files that was an issue, it wouldn’t even let me run the application because of low hard disc space. Monitoring Memory Usage In Windows In this section I learned about the Windows task manager and how to understand the information it gives you. In task manager there’s a performance utility tab, this allows you to see your memory usage. You access this by pressing ctrl + alt + delete. Then checking the performance tab. This shows you graphs of your CPU usage and memory. I learned about different types of memory information and general information the memory usage page gives you such as total, cached, available, and free physical memory, paged and nonpaged kernel memory, handles, threads, processes, up time, and commit. Total physical memory is the amount of RAM installed. Cached physical memory are the memory pages that you could write to disk and make available. Available physical memory is the amount of memory that can be used for applications both in the physical memory and the written pages. Free physical memory is the amount of available RAM physically. Paged kernel Memory is the memory in pages that can be used by applications and frees up RAM. Nonpaged kernel memory is memory that’s only available to the operating system and stays in RAM. Handles are the number of resources the operating system is currently using. Threads are the number of objects within current processes that are doing instructions. Processes are programs that can be run or executed. Uptime is how long the system has been running. Commit is a list of the requests for virtual memory. If this charge is more than the total amount of physical memory, the system is paging too much and you need to add more RAM. I also learned that in Windows Task manager there are 4 sections of information about memory, in use, modified, standby and free. Memory in use is memory currently being used. Modified memory is memory that has data that needs to be written to the drive or else that memory location can’t be used by something else. Standby memory is memory that is cached and not being used. Free memory is available memory. This section was interesting to me because we actually just used the windows task manager section in the lab we did. So I got to actually use this and see the graphs and sections this reading talked about. I also enjoy learning about systems but also learning about practical things like literally how to use this program on a computer. It’s also helpful to me because I know how to check my activity on a Mac because I used the activity monitor to find a virus that was obviously running on my friend’s computer and I’ve used it to check what tabs are taking up a lot of my CPU power. But I don’t really know anything about windows so this was helpful to understand how to use the windows activity monitor. Flash Memory In this section I learned about flash memory. Flash memory is a non-volatile, solid state memory that can hold data when the computer is shut off. A lot of devices use flash memory. Cameras store pictures on flash memory, some tablets use it, network devices, phones and tablets use flash memory to store the operating system. This section was interesting and pertinent to me since I’ve used flash memory everywhere. I’ve used flash drives or USB sticks to store data since I was in elementary school, I’ve used SD and micro SD cards in my camera. During covid I started learning about raspberry pi and I built a robot, and to download the operating system for the robot I had to write the OS file to the microSD from my computer then insert it into the raspberry pi. The operating system was stored on that microSD. It was also cool to see the image of a flash drive because I’ve just never seen the inside even though I’ve used them all my life and I didn’t think about the fact that there's a little motherboard inside.