Overview of PC Memory - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer





  • So if your PC loses power and you lose everything you were doing, how does chrome ask to refresh your last session? Is it something in their software?



  • @mary said in Overview of PC Memory - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:

    So if your PC loses power and you lose everything you were doing, how does chrome ask to refresh your last session? Is it something in their software?

    All software can do that. If it is written to do so in the first place.



  • Many systems have this built in today. Each component is doing it's own form of autosave - then when the system recovers, it brings those choices back for you.

    In a way it's a bit creapy... Windows 10 with Office 2016 or higher - if WIndows reboots, upon log back on, the apps that were open will reopen. Not sure this will happen if you have a sudden power loss though.



  • @mary said in Overview of PC Memory - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:

    So if your PC loses power and you lose everything you were doing, how does chrome ask to refresh your last session? Is it something in their software?

    Basically it keeps a log. So think about making any application of your own. Doesn't really matter what it does. When you write your software, you can decide that anytime a user does something (or something significant) that you simply log that action. You don't even have to think about software, imagine humans doing this with paper...

    Two humans playing a board game. Monopoly, Clue, whatever. Every turn, they keep a journal of what was done or what the current state of the game is like where the pieces are and what pieces people have.

    Then a two year old runs through the room being chased by a dog (or vice versa) and knocks everything onto the floor, spills mommy's wine on her white jogging pants, etc.

    Three hours later after cleaning things up and putting little Billy to bed, you return to the game, put the board back in place. You go through your journal and see where everything was. Simply by keeping either a journal of events and/or a simple "current state" log, you can go right back to where you were.

    For something like Chrome, all it needs to do is maintain a small file with a list of URLs that you are currently on and update it as it opens a new one or closes one. Takes a couple milliseconds to do. And it does it while the tab is opening or closing. It doesn't need to wait for the journal to do it, it can do it as it happens, so no delay to you.



  • It's similar to how Word will save your progress, but didn't used to. With disks being so much faster now, especially compared to floppies, writing changes automatically isn't a big problem for most things.



  • How does DDR2 have a higher transfer rate than DDR if they have the same clock speed?



  • @connorsoliver said in Overview of PC Memory - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:

    How does DDR2 have a higher transfer rate than DDR if they have the same clock speed?

    Instead of transferring a single piece of data with each clock tick, DDR2 sends data on both the uptick and downtick for each clock. This is vastly simpler to understand with a graph, but I don't have time to make even one of my bad drawings at the moment.



  • @connorsoliver said in Overview of PC Memory - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:

    How does DDR2 have a higher transfer rate than DDR if they have the same clock speed?

    A clock speed is a measurement of measurement granularity not a measurement of performance.

    Think about a clock in the room with you. Whether it has a second hand that sweeps by every 60 seconds, or only shows clicks on the minute, doesn't directly impact how much you can do in an hour.



  • DDR2 uses a clock speed twice as high as the bus speed. So DDR2 is double the speed of DDR given the same bus. The clock that the computer provides to the RAM is the same speed. But the memory clock speed in these cases as either 1x or 2x the bus speed from the computer. So the clock speed is double.