In a similar vein, why can we not use the technology of RAM to prolong the life-cycle of an SSD?
Writing to an SSD damages the SSD, however things saved to an SSD are persistent, meaning the data isn’t lost when the SSD doesn’t get any power. Writing to RAM doesn’t damage it and it is also quicker. However, data saved on RAM is not persistent, meaning that all data is lost as soon as the RAM is not connected to a power source. Also, RAM is a lot more expensive than SSD storage.
RAMs are already used to avoid writing to (or reading from) the SSD or HDD when possible, the concept is called “Caching”
Even if it’s powered, RAM will lose its data on the order of a tenth of a second. RAM doesn’t just require power, it requires that your computer constantly read and rewrite it - so every 64ms your computer has to read every gigabyte of RAM and write it back.
Doesn’t the ram do that itself? Otherwise reading/writing all that data would waste tons of time for the CPU.
Yes - it’s been the job of the DRAM controller for almost the entire history of computing. But that’s still a part of the computer and if it stops working then your RAM will go blank in a fraction of a second
What!
If you ever have the chance to use an old Apple II computer, run a text mode program, wait til the owner is looking in the other direction and turn the power off and back on quickly.
For about a second, before you hear the loud BOOP and the screen clears, you’ll see whatever was on the screen just before you powered it off. But a few characters will be corrupted. Try it again, and wait a half a second longer than before. More characters will be corrupted.
For that brief second you’re looking at the contents of the video RAM, then the ROM (Apple called what we call BIOS now “ROM”) clears the contents and puts up the familiar text banner. The longer the power stays off, the more the contents of those RAM cells decay, and any bit flip will show up as a different character at the corresponding location on the screen.
On a side note, there was an article in the early '80s in Circuit Cellar by Steve Ciarcia showing how you could make a rudimentary digital camera by prying the top off a DRAM chip (some were ceramic with metal lids, or just metal cans) and adding a CCTV camera lens at the right distance. Light can deplete the charge in DRAM cells even faster, and by writing all 1s to the memory, exposing it to light, and reading back the contents, you could get a black and white image of whatever’s shining on the chip.
The camera hack is really cool - i love stuff like that.
so people have said that it’s to do with volatile (it forgets) and persistent/non-volatile (it remembers), but i think the crux of your question is a little more nuanced: WHY does the mechanism to “remember” a 1 or a 0 get damaged with SSDs and not for RAM
now, i’m not expert here but i think i have a basic understanding and i’ve pieced some bits od research together!
(edit: it should be noted that what ive described here as simply “RAM” is actually SRAM, but modern computers mostly use DRAM which is different: it uses a capacitor instead of a couple of transistors, but the fundamental idea is the same)
RAM is very simple: for the most part, it’s just a few transistors - they’re basically little switches that work just with electrical current… they can be arranged so that transistors connect to another transistor, so that they’re both telling each other to be “on” (this is SUPER simplified, but kinda think of the electricity being stuck in a loop: it just goes round and round between the transistors, and that’s “on” or 1)… transistors are very reliable! their chemistry doesn’t degrade over time (note though that because electricity doesn’t actually go around in an infinite loop, if the “loop” stops getting power to replenish it, it resets to 0, which is what makes it volatile!)
SSDs though store their 1s and 0s more in chemicals… think of your SSD like a bunch of little boxes with water in them, and you read the 1s and 0s based on how clear the water is… you add sand to make a 1, and you filter out the sand to reset it to a 0! the more often you do that though, the dirtier the water gets until you can’t tell if it’s just dirty water of if it has sand in it (actually you add electrons to the gates in an SSD which changes the cells resistance and you read based on that, but at some point the electrons just keep ”sticking” in the cell so the resistance doesn’t change as much as we’d like)
SSDs typically use flash memory, as I understand it. I’d leave the sand out and say it’s like a tank you fill up with (more or less depending on the data) water. After a while the tank mechanically wears out and starts to leak. Flash memory very much is like a tank filled with electricity and then plugged, and it does start to leak as the insulating oxides degrade.