My 9/21/08 Missoulian column
As I wrote last week, hard drives have a tendency to not “forget” your files. There is another type of memory that works very differently than a disk drive, and both kinds work in conjunction to run your PC. The second type of memory is called RAM, which stands for random access memory, but most everyone says RAM, or just “memory.”
The physical differences between the two are hard drives have moving parts – such as the disk “platters” that hold the data and the arm that moves across them, reading and writing – and look like little metal boxes. RAM is made of integrated circuits, or “chips,” mounted on plastic sticks and are small and flat. And the electronic differences are that disk drives record information on the magnetic surfaces of those platters, and RAM stores information in the electronic cells of the integrated circuits.
But the big differences a PC user should know about are speed, volatility and capacity. RAM is much faster than a disk drive, which is slower because it has moving parts – the disk and the arm that scans the surface of the disk to read and record – while RAM is fast because it is all electronic.
Volatility isn’t so obvious; it doesn’t mean your PC is in danger of bursting into flame. It has to do with remembering your files when the power is off. Hard drives won’t forget when the power is off – that’s called nonvolatile memory – while RAM will instantly forget when the power goes off.
Capacity is just that: how much data the memory can hold. Disk drives in your PC have much more capacity than RAM because the disk has to store all your files, programs and the operating system, while RAM is for short-term storage as your PC is running. Your PC would be the size of a small fridge if it had the same amount of RAM – and the necessary power supplies, cooling fans and boards – as hard drive capacity.
The two types of memory work in conjunction because your PC needs both kinds: fast, temporary RAM storage for working, and long-term disk storage that doesn’t need to be as fast but needs to “remember” when the power is off.
Hard drives and RAM work together in this way: When you turn your PC on, most of the startup time is accounted for by the hard drive loading programs and the operating system from it’s long-term storage into short-term RAM for you to work. When you save a file, it takes a little bit of time to go from RAM to the hard drive, because the hard drive is slower. But then the file will be safe when you shut down the PC.
In order to make your work efficient and save your files, RAM and the hard drive are constantly trading off files through lots of different processes run by the operating system. Both memory types work to their particular advantages to keep things running smoothly.
The lines between memory can get blurred, though. If you don’t have as much RAM as a program happens to need, part of your hard drive is used as a kind of RAM. The operating system will detect this shortfall and start to use part of the hard drive as “virtual memory”; memory that is not real hardware, but is usable because the software can’t tell the difference.
Of course, because hard drives are slower than RAM, virtual memory is slower than real RAM. When your hard drive is really rattling around and things work slow, chances are good that one thing the operating system is doing is using virtual memory on the hard drive.
So, how much hard drive capacity and RAM do you need? Most of the time the hard drive in a brand-new PC has much more capacity than you will need. Unless you suddenly start downloading lots of music and moves, you’ve got more room than you will use. The cost of hard drives continues to drop in terms of dollars per gigabyte, and PC manufacturers like to install large-capacity drives as a selling point. 120 gigabyte to 160 GB drives are about the minimum these days, and few people will use that capacity.
But much of the time you will want more than the usual amount of RAM. More RAM means more room for programs to run without having to use the hard drive for virtual memory. It also can be cheaper to buy more RAM with a new PC rather than install it later, and that RAM will be covered under the warranty.
RAM keeps falling in price, so if you’re buying a new PC or laptop, consider getting a minimum of 2 GB. If you get 4 GB or more, Windows and OS X will be very happy and will run fast for not much more of an investment.
When you have lots of RAM, you’ll see a huge difference in memory-intensive programs such as Photoshop. And video editing needs large amounts of RAM (and hard disk capacity, too). Check the minimum requirements for the software; you might need 10 GB or more.
Like anything high-tech, there is always the “next big thing,” and in the world of PC hard drives, these are solid-state drives, or SSDs. They have the large capacity of a hard drive but are made with RAM-like chips, and so have the speed of memory and the capacity of a hard drive. SSDs promise to be the best of both worlds, and a PC with an SSD will be “instant on,” too.
SSDs are expensive right now, but after they become more of the norm than the exception, I suspect they won’t be called “solid-state disks” anymore, and history might relegate the phrase “disk drive” to the dustbin of the computer world.
Followup on semantic search: A company has announced it has built the largest semantic map of the English language with 10 million “connections” between words, but isn’t going to compete with Google just yet.