Why does RAM memory disappear when power switches off, but HD/SSD memory stays intact regardless of power status?
In: Technology
HDD (hard disk dives) have a physical disk in them where data is stored. Sections of the disk are magnetized or demagnetized to store information. In terms of data storage, they are closer to CDs, DVDs, and blue rays than RAM and SSDs.
RAM uses traditional transistors and capacitors to function. Imagine a pushbutton switch. You press it to turn it on and when you let go, it turns back off. If you leave (ie you loose power) the switch turns off and there isn’t away to tell if the switch is off because it was supposed to be off, or because you left. the transistors in SSDs are more like light switches. There are two stable states, either up or down. If you’re flipping the switch and you walk away, it stays in the last position you put it.
RAM is what is called “dynamic” memory while the other kinds you mention are considered “static” memory. RAM trades being volatile (losing contents if you turn it off) for speed, cost and size. It also helps when memory bloat starts making programs act up to have the memory wipe with a restart.
Static RAM used to be much more a thing back in the 80s or so. But it’s not really necessary to keep the contents of RAM typically, while an SSD or HDD are specifically designed to keep contents.
Because of its design.
RAM stores bits in a bunch of capacitors. These are devices that store electricity in them, but can’t do so for very long, they need to be periodically refilled and there is circuity to refill them, and that requires electricity. If no power is provided, the capacitor discharges and it all becomes 0s.
This is also a feature and not a bug. The ability to reset ram to all 0s under any situation solves issues when a computer is glitched. Imagine turning the computer off and on and it doesn’t unglitch because its still running code off the same ram that was glitched since it wasn’t wiped.
Hard Drives use disks that are magnetised to store bits. SSDs use a little trick known as a floating gate mosfet which traps electricity (without being able to discharge over time like a capacitor), which stores bits without power.
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