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MTBlogBot2000
20th September 2010, 02:02 PM
<a href="http://www.mactalk.com.au/wp-content/uploads/2010/09/ComputerJunk.png"><img class="alignright size-full wp-image-9745" src="http://www.mactalk.com.au/wp-content/uploads/2010/09/ComputerJunk.png" alt="" width="300" height="200" /></a>Every Mac has RAM (or memory) installed - without it, the computer wonít even start up.

Pretty much every Mac also has a hard drive. If not an actual hard drive then itís new, souped-up cousin, the SSD (or, solid state drive).

We all know that having both is important. We also pretty much understand that the more you have, the better off you are.

From here, though, we start to run into all sorts of confusion, contradictions and misunderstandings.

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<h2>What is RAM?</h2>
Think of RAM as being a little like your computer desk (or, office desk, or study desk, if you prefer). If youíve got a really small desk thereís not much room to move. Every time you want to use your desk you have to move out all the stuff that you were already using to clear some space. With a larger desk, you donít have to clear out what youíre already using to do something else.

<a href="http://www.mactalk.com.au/wp-content/uploads/2010/09/RAMLineUp.png"><img class="alignright size-full wp-image-9746" src="http://www.mactalk.com.au/wp-content/uploads/2010/09/RAMLineUp.png" alt="" width="300" height="200" /></a>Once you finish work and go home, it no longer matters how much desk space youíve got. Youíre done using it.

RAM works the same way.

Without enough RAM every new program you start up will need some space. If thereís not enough space itíll try and clear some out through a variety of mechanisms that OS X provides. The more RAM you have, the more things you can have open at once. This can either be multiple photos, document, or spreadsheets in one program or having multiple programs running.
<h3>How much RAM?</h3>
There isnít any one answer to this question. Everybody is different. What you do with your computer will determine how much RAM is right for you.

If youíre using your Mac for email and some casual web surfing, donít worry about how much RAM youíve got, itís almost certainly enough.

If youíre manipulating digital photos in RAW format, editing video or other similar tasks then the more RAM youíve got, the better off youíll be.

Thereís a school of thought that says you should get as much RAM as you can in your computer when you buy it. If youíll be using your computer for tasks that need RAM Iíd agree completely. If not, Iíd suggest holding off on upgrading your RAM. As a general rule, the price of any particular type of RAM drops over time. RAM that might cost $200 today may be available for $100 in six months time. Waiting until you actually need that extra RAM can save you some money.

At the same time, if you wait too long, RAM pricing will start to rise again as it ceases to be commonly used and, as a result, the sales volumes decline.
<h3>Do I need more RAM?</h3>
You may benefit from adding more RAM if:
<ul>
<li>your computer is very slow to start up.</li>
<li>it takes a long time to load a new program.</li>
<li>your computer is fairly sluggish or unresponsive when youíre using it.</li>
<li>you plan to (or already) use a virtual computer via Parallels, VMWare, etc.</li>
<li>you expect to work with large photos or videos</li>
</ul>
<h3>How much RAM am I using?</h3>
When your Mac is booted and running, go into Applications, then into Utilities and start the Activity Monitor. The Activity Monitor is a window into the inner workings of your Mac. When youíre viewing the System Memory tab youíll see something like this:

<a href="http://www.mactalk.com.au/wp-content/uploads/2010/09/ActivityMonitor-Memory.png"><img class="aligncenter size-full wp-image-9749" src="http://www.mactalk.com.au/wp-content/uploads/2010/09/ActivityMonitor-Memory.png" alt="" width="500" height="150" /></a>

Free memory is the amount of RAM thatís not being used at all.

Wired memory is memory thatís in use and canít be shuffled around to free up RAM if needed.

Active memory is the amount of RAM currently (or relatively recently) used.

Inactive memory is RAM thatís been used recently but isnít in current use. For example, if youíve just closed a program then OS X will keep track of it for a while so that if you load that program again itíll load faster.

Used memory is the total RAM in use.

If you add free and used memory you should get fairly close to the total RAM in your computer (it wonít always be exact because you may have shared video memory and thereís also some rounding errors in the totals for each type of memory being counted).

If you have only a very small quantity of free RAM as well as a small quantity of inactive RAM then you would most likely benefit from adding RAM to your Mac.
<h2>What is a hard drive?</h2>
<a href="http://www.mactalk.com.au/wp-content/uploads/2010/09/HDDInnards.png"><img class="alignright size-full wp-image-9752" src="http://www.mactalk.com.au/wp-content/uploads/2010/09/HDDInnards.png" alt="" width="300" height="199" /></a>Think of a hard drive as being a little like a filing cabinet. Itís a place to store your stuff when you arenít using it. The larger your filing cabinet, the more room you have to store your stuff.

In computer terms, the hard drive is where you store things like photos, music and videos. Itís also the place that holds your operating system and all the programs that you use.

When you run a program, your computer reads that program off your hard drive and then loads the bits it needs into RAM. Only once the program is loaded in RAM can you use it. The same thing happens with, say, a photo that you want to edit or a song you want to play. It first loads that information into RAM and then does something with it. Because programs and data can be really large, the operating system (and the applications) can do this loading in chunks - only loading the bits actually needed into RAM while leaving the rest ready to go on the hard drive.

When you close a program, or a photo, it gets removed from RAM and once again is only on the hard drive.

Once you finish work and go home, it still matters how much filing cabinet (or hard drive) youíve got. Itís where everything is stored when youíre not using it.
<h3>How much hard drive?</h3>
As with RAM, thereís no one answer. It depends on what youíre doing.

If youíre into digital photography, or collecting music and video, then a big hard drive is essential. If youíre not like this then a smaller hard drive will be just fine.

These days, itís rare to see any computer with less than around 250GB of hard drive space. For most people, this will be plenty. A typical point-and-shoot digital camera might be taking photos that are 1MB in size - you can fit more than 1,000,000 photos on a 250GB hard drive. One GB of hard drive space would be enough to hold the full contents of the books on a bookshelf around 10m long.

Unless youíre hoarding lots of music, videos and photos, youíve probably got enough hard drive space.
<h3>Do I need more hard drive?</h3>
You may benefit from more hard drive if:
<ul>
<li>you get a warning about low disk space very time you download from iTunes</li>
<li>your computer is very slow to start up.</li>
<li>you plan to (or already) use a virtual computer via Parallels, VMWare, etc.</li>
<li>you expect to accumulate heaps of digital media (such as photos, video, music, etc).</li>
</ul>
<h3>How much hard drive space have I got?</h3>
Refer to the recent MacTalk article about <a href="http://forums.mactalk.com.au/showthread.php?t=91676">Visualising Disk Usage</a>.
<h2>Confusion:</h2>
<blockquote>My computer is running very slow - so I need a bigger hard drive.</blockquote>
That may be true, or not.

Without more information itís impossible to say.

Check how much hard drive space youíve got before you go trying to delete stuff or move to a bigger hard drive. You might benefit more from increasing RAM.

Unfortunately, your computer can also be running slow for reasons that have nothing to do with either RAM or hard drive. This might include run-away tasks (programs) that are consuming all your CPU cycles, hardware faults that get in the way of your computer operating normally, and so on.

When dealing with computer problems, the symptoms you see are only indicators. Itís almost impossible to really know whatís wrong based on only one symptom.

<em>David Freeman is an Apple Certified Macintosh Technician and the proprietor of Outback Queensland Internet (aka <a href="http://www.leclre.com.au/">Leading Edge Computers Longreach</a>). He has worked as a technician for over fifteen years and been involved in computers and the Internet since 1988 when he purchased his first computer (an Amiga 1000).</em>

elnewb
20th September 2010, 02:52 PM
Sorry to nitpick.... but


The more RAM you have, the more things you can have open at once.

OS X will just move the contents of RAM onto your HDD as VRAM (Virtual RAM) when it runs out of space. So it's not limited by the amount of RAM installed.


Used memory is the total RAM in use.

It says "Used" but it's not actually in use. It includes Wired, Active and Inactive. Inactive is memory that is not in use but has been RECENTLY used and not over-written and should be treated as available RAM not "used RAM. It's a caching technique used to increase performance. It is freed for use when the "Free" memory runs out.

I think the tone of the article should be less "RAM is directly equivalent to speed" and more "More RAM allows more tasks to be run at your machines maximum speed".

And finally there's these two pieces of gold...


<h3>How much hard drive?</h3>

<h3>Do I need more hard drive?</h3>

This is very poor English.

Brains
20th September 2010, 03:37 PM
"I'm not too clear on all this rams and hard disk stuff, what's the difference? And why should I have more of either of them?"

"it's really quite simple, Mum. Imagine the kitchen counter-top is your computer's memory, the RAM, and all the kitchen cupboards is the computer's hard drive. The bigger your counter-top is, the more things you can do at once on it. If you need to do something and there's no space on the counter-top, you have to put something away in the kitchen cupboards first before you can get the other stuf out to put on the counter-top."

"Oh. Oh! Yeah, I get that, thanks!"

[true story!]

dotnet
20th September 2010, 04:19 PM
I think the tone of the article should be less "RAM is directly equivalent to speed" and more "More RAM allows more tasks to be run at your machines maximum speed".

More RAM may well be directly equivalent to speed, especially with slow HDDs such as the ones found in laptops. Inactive memory is essentially disk cache which saves the OS a trip to the HDD when reading files (program or data). The more cache the less dependent you'll become of slow disk IO.

What many people don't realise is that the green wedge ("free") is part of this caching strategy as well. It incorporates not just free memory (i.e. memory that isn't used for anything at all) but also speculative memory. Speculative memory is file data that the kernel caches in case it might be used. For example, file read-ahead data is cached in memory in the speculative state. Also, when a program writes sequentially to a file, that data is cached in memory as speculative as well. The amount of speculative memory in use is shown by vm_stat.

All this caching (inactive plus speculative memory) requires a surplus amount of RAM to be available. There is no such thing as too much RAM, unless you're not using the computer for anything at all and need no disk IO. Loads of extra RAM can easily be shown to speed up apps that perform large amounts of disk IO, such as Aperture.

Cheers
Steffen.

glacierdave
20th September 2010, 06:05 PM
I take the comments on board, however, I'd like to suggest that the article was largely intended for an audience that's confused by the terms "ram" and "hard drive".

On that basis, a drift off into the ins and outs of exactly what constitutes, for example, "used memory" isn't really going to add much, nor is discussing swap space, virtual RAM and a host of other things that can help get around the fact that you don't have enough to start with.

All fair comments and accurate, but I maintain that they don't necessarily constitute detail that needs to be in this particular article for an audience that doesn't know it's RAM from it's hard drive.

doconmac
20th September 2010, 06:13 PM
An excellent analogy which I shall use at our MUG meetings for teaching

dotnet
20th September 2010, 06:27 PM
I take the comments on board, however, I'd like to suggest that the article was largely intended for an audience that's confused by the terms "ram" and "hard drive".

Nothing wrong with that, and I didn't make my comment as an addendum to your article. It was a reply to the quoted passage from elnewb's post that I took issue with.

Cheers
Steffen.

feeze
20th September 2010, 07:27 PM
Good article.

Although I think there is one thing that should be stated very concisely as I've seen it cause a tonne of confusion.

When a computer person uses the word 'memory' they are talking about RAM. When a computer person is talking about 'storage' they are talking about a hard drive, etc.

A hard drive is NOT called memory. Have low amount of hard drive space left is NOT being low on memory or running out of memory.

Sounds pedantic, but in my experience the misuse of terminology causes a great deal of confusion. Especially when trying to solve a problem.

Paul_G
21st September 2010, 09:48 AM
Good article.

Although I think there is one thing that should be stated very concisely as I've seen it cause a tonne of confusion.

When a computer person uses the word 'memory' they are talking about RAM. When a computer person is talking about 'storage' they are talking about a hard drive, etc.

A hard drive is NOT called memory. Have low amount of hard drive space left is NOT being low on memory or running out of memory.

Sounds pedantic, but in my experience the misuse of terminology causes a great deal of confusion. Especially when trying to solve a problem.

True. The confusion is understandable though - and it's the IT sector that has caused it. The word 'memory' has meant 'storage of things that have happened to us' for centuries, so in general usage 'memory' and 'storage' are effectively the same.

To describe how much we (as people) can multitask, how much we can process, how hard we can think - we use words like intelligence, brainpower, smarts, mental agility, processing power, brainpower... all sorts of terms, but NEVER 'memory'.

Thinking isn't the same as remembering. Even really dim people can have a lot of memory.

I realise this is just how it is, but it's important for us to keep in mind that the IT sector's use of the word memory is counterintuitive, so be patient with our non-geek friends!

Edd
21st September 2010, 09:39 PM
RAM is "memory" though. And we do use words like "memory". Think of "short-term memory" (RAM), vs "long-term memory" (HDD).

Common usage has made HDD generally referred to as storage, but if you look at a computer science memory hierarchy in order of speed, you will see that it goes from working registers, cache (SRAM), RAM (DRAM), SSD, HDD, Optical, etc. All of these are valid types of memory, but common usage has led to the term "memory" to mean the dynamic RAM, at least without further clarification.

It's not incorrect to call hard drive storage "memory".

I personally think the confusion comes from the average person's willful ignorance of technology. Or the general idea that trying to understand something is too hard so it's better to just never learn new things.

Pretty good article at explaining the basics.

1000
22nd September 2010, 06:14 AM
Nice analogy re mum and the kitchen cupboard. I used a similar one on my father.. I described his workbench in the garage , his tools taken from the wall and placed on the bench while he worked was RAM/memory and the tools in his drawers were his HDD, far more familiar for men !!!!

1000