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Laptop buying guide part one: Confused memories of a computer shopper – L2 Cache, RAM and Hard Drive

What does all this mean??? Read on to find out...

Computer shopping has always been about specs and stats. That’s unlikely to change anytime soon and it’s important to understand the key vital statistics. Memory choices are critical to the performance and longevity of your purchase, so here in the first of this two part laptop buying guide is the memory geek-speak translation.

Memory tech words which tend to pop up on sales listings are RAM, L2 Cache and Hard Drive (also called Hard Disk). In order to understand them we are going to imagine ourselves in a library.

What is L2 Cache?

In our library there are bookshelves, desks and chairs. We walk in, find twelve books from the bookshelves and put them on the floor next to a desk. We sit at the desk but it’s only big enough for a few books with enough space left for us to work. So we pick the three books we need right now from the floor pile and put them on the desk.

The desk is our most convenient and fastest retrieval location for referencing our books. It’s also the smallest. This our Level 2 Cache, or L2 Cache.

The L2 Cache is a temporary storage space used by computers for ultra-fast access to frequently used data. When we take a book from the desk and start reading it with our brain and eyes, this like a computer retrieving data from its L2 Cache and reading it with its main processor chip. The L2 Cache is actually located within the main processor itself, so it is a physically small storage area of around 0.5-12MB.

How much L2 Cache do you need?  I would recommend 1MB upwards for Mac OSX, Windows 7 or Vista.  Netbooks running Windows XP are fine with 0.5MB.

Expert question: Why is it called Level 2 Cache? There is actually a tiny cache even closer to the main brain in the processing chip called Level 1. However this is so small that it is really only used for very temporary storage and rarely quoted in store listings.

What is RAM?

What if we need to read a book which is not on the library desk? We look in our pile on the floor. This is a bit slower than using a book already on the desk, but we can put more books on the floor than we can fit on the desk. Looking in the floor pile is like a computer using its Random Access Memory (RAM).

Accessing data in RAM is fast, but slower than the L2 Cache as it sits outside the main chip and connects via fast data lines like our floor pile of books. Since RAM is not constrained by the physical real estate limitations of the main chip, it can store far more data. RAM sticks with capacity of around 0.5 to 1 gigabyte are common these days. Computers typically accommodate two such ‘sticks’.

How much RAM do you need? For Windows 7, Vista and Mac OSX 2GB is typically fine, but it’s worth going to 3GB if you are planning to use a lot of multimedia applications like video or photo editing.  This will give the computer some breathing room.

What is the Hard Disk?

If the library book you need is not in the floor pile then you have to get up, walk over to the bookshelves, find the right book and bring it back. This takes way longer than picking it up from the floor pile, but the bookshelves can store far more than your floor pile. The bookshelves are like a Hard Drive. They can store vast amounts of information and Hard Drive data remains intact when the computer shuts down, unlike your desk and floor piles which you will clean up when you leave.

Hard Disk data is stored on a set of spinning platters which are read by a needle. The occasional ticking noise you hear in a computer is the Hard Disk being physically read.

How much Hard Disk space do you need? External Hard Disks can be easily bought and plugged into a USB port, so it is not critical if you under-purchase. However with laptops it becomes inconvenient if you run out of space, as although you can add an external drive you are unlikely to want to carry it along with your laptop. So for laptops my advice is to buy a machine with as much Hard Disk space as you can afford; look for a laptop with upwards of 160GB capacity. Video, photo and music files are typically large so if you plan to store lots of these then max-out on your Hard Drive at purchase all the way to 320GB or more.

It’s worth knowing that you cannot control what gets stored in RAM or in the L2 Cache. The computer decides what to put in there, such as open files the in process of being modified. When you turn the power off anything in the L2 Cache or RAM gets wiped, whereas data in the Hard Disk remains intact when the power is off. Similarly you clear the desk when you leave the library and return any books to the bookshelves. This is why it is important to save any open files before shutting down a computer.

What laptop upgrade options exist?

For the L2 Cache, the only expansion route is to replace the main  processor, which is typically only feasible for a desktop computer.

Laptop RAM can normally be upgraded as long as the computer’s motherboard is able to handle the extra capacity. For example my older MacBook is unable to accommodate more than 2GB of RAM. If your laptop can accept an upgrade from your current RAM level then it is normally a case of removing the existing RAM sticks and fitting correct spec higher capacity ones.

Laptop Hard Disks can generally be upgraded, but it is a delicate process which involves cloning the data from the current drive onto the higher capacity drive in a precise way. The alternative we discussed earlier is to purchase an external Hard Drive, which are readily available these days at reasonable prices.

When laptops go bad: Holding back the tears

Finally, when a laptop gets sick (read “dropped”) or feverish (read “struck by a virus”), its Hard Disk can be vulnerable to permanent amnesia. So, be nice to yourself and buy an external Hard Drive to back up your photos, music and all those other precious memories.

So that’s the translation of memory geek-speak. Here’s hoping for clear thinking for your next purchase and an end to confused memories!

I originally wrote this article in 2007 and have updated it to reflect the 2009/2010 laptop market.

Neil Berman

Click here to read part two: How to choose a laptop processor (2007).


Nov 21, 2009 - Posted by | Computing, Guides, Hardware, Mobile | , , , ,


  1. Really nice article, very well taught, I understood it very well. Being a common man, I think you must be a nice teacher.

    Comment by Yog Raj | Nov 6, 2009 | Reply

  2. Thank you for the basic information about all these stuffs.
    keep posting.

    Comment by Cheap Fujitsu Laptops | May 3, 2010 | Reply

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