How can computer scientists improve computer memory, ensuring saving things is more secure? If Vasileios Klimis of Queen Mary, University of London’s Theory research group has his way, they will be learning from bats.
Imagine spending hours building the perfect fortress in Minecraft, complete with lava moats and secret passages; or maybe you’re playing Halo, and you’ve just customised your SPARTAN with an epic new helmet. You press ‘Save’, and breathe a sigh of relief. But what happens next? Where does your digital castle or new helmet go to stay safe?
It turns out that when a computer saves something, it’s not as simple as putting a book on a shelf. The computer has lots of different places to put information, and some are much safer than others. Bats are helping us do it better!
The Bat in the Cave
Imagine you’re a bat flying around in a giant, dark cave. You can’t see, so how do you know where the walls are? You let out a loud shout!
SQUEAK!
A moment later, you hear the echo of your squeak bounce back to you. If the echo comes back really, really fast, you know the wall is very close. If it takes a little longer, you know the wall is further away. By listening to the timing of your echoes, you can build a map of the entire cave in your head without ever seeing it. This is called echolocation.
It turns out we can use this exact same idea to “see” inside a computer’s memory!
Fast Desks and Safe Vaults
A computer’s memory is a bit like a giant workshop with different storage areas.
- There’s a Super-Fast Desk right next to the computer’s brain (the CPU). This is where it keeps information it needs right now. It’s incredibly fast to grab things from this desk, but there’s a catch: if the power goes out, everything on the desk is instantly wiped away and forgotten! If your data is here, it is not safe!
- Further away, there’s a Big, Safe Vault. It takes a little longer to walk to the vault to store or retrieve things. But anything you put in the vault is safe, even if the power goes out. When you turn the computer back on, the information is still there.
When you press ‘Save’ in your game, you want your information to go from the fast-but-forgetful desk to the slower-but-safe vault. But how can we be sure it got there? We can’t just open up the computer and look!
Shouting and Listening for Echoes
This is where we use our bat’s trick. To check where a piece of information is, a computer scientist can tell the computer to do two things very quickly:
- SHOUT! First, it “shouts” by writing a piece of information, like your game score.
- LISTEN! Immediately after, it tries to read that same piece of information back. This is like listening for the “echo”.
If the echo comes back almost instantly, we know the information is still on the Super-Fast Desk nearby. But if the echo takes a little longer, it means the information had to travel all the way to the Big, Safe Vault and back!
By measuring the time of that echo, computer scientists can tell exactly where the write went. We can confirm that when you pressed ‘Save’, your information really did make it to the safe place.
The Real Names
In computer science, we have official names for these ideas:
- The Super-Fast Desk is called the Cache.
- The Big, Safe Vault is called Non-Volatile Memory (or NVM for short), which is a fancy way of saying it doesn’t forget when the power is off.
- The whole system of close and far away memory is the Memory Hierarchy.
- And this cool trick of shouting and listening is what we call Memory Echolocation.
So next time you save a game, you can imagine the computer shouting a tiny piece of information into its own secret cave and listening carefully for the echo to make sure your progress is safe and sound.
– Vasileios Klimis, Queen Mary University of London
More on …
- Computer Memory [PORTAL]
- Theory, Logic and Deduction [PORTAL]
Getting Technical …
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