RAM Cram 101: How Much Memory Do You Need?

by - Episode 19 - June 11th, 2004

Every time I review a new Mac, I say the same thing: The default configuration does not come with enough RAM to run Mac OS X decently. Even today's baseline configuration (256MB) isn't enough RAM for most people most of the time. And unfortunately, when your Mac is starved for RAM, everything you do will be slowed down as your Mac tries to use your much slower hard disk in place of the RAM it so desperately needs.

For what it's worth, I write about this situation every chance I get -- in columns and books -- because many new Mac owners don't know that an inexpensive RAM upgrade will almost always improve a stock Mac's performance.

The key to figuring out if your Mac needs more RAM is a statistic known as the "pageout," which means a "page" or memory is being written "out" to the drive. In low memory situations your Mac will substitute slow hard disk space for the fast RAM it wishes were available. So when your Mac is paging out frequently, it's almost certainly not running as fast as it would if you added additional RAM.

Over the years I've recommended using programs like Memory Usage Getter, Memory Stick, or the UNIX "top" command in the Terminal for evaluating your RAM usage and viewing pageout statistics.

Memory Usage Getter is one of my startup items (formerly, and more correctly known as Login Items), and it runs 24/7 on all of my Macs. It's a fantastic US$10 shareware program by Simone Manganelli that can tell you when you're using all of the installed RAM as well as how much RAM (and CPU cycles) individual applications and processes are using:

While Memory Usage Getter doesn't provide actual pageout statistics, the bar graph at the bottom of both of its windows provides real-time feedback on how much RAM is currently available. When I see the amount available fall below 20 megabytes, I know I'm about to start paging out and that my Mac isn't running at its top speed.

That rarely happens since I upgraded my G5 to 2GB of RAM. Even when I have 15, 20, or even 25 programs running I have lots of RAM available.

But this isn't about me…so let me show you another way to monitor your Mac's RAM usage, namely, Matt Neuberg's free MemoryStick:

MemoryStick is a resizable bar chart that indicates how your RAM is being used. It's resizable and unobtrusive and has a killer trick hidden in its Options menu -- the ability to alert you when pageouts occur. With MemoryStick, the smaller the gray area (Free RAM) on the bar chart the more you'll hear the pageout alarm. And the little black dot on the right side of the MemoryStick window will blink when pageouts are occurring.

I'm not going to demonstrate the UNIX "top" command here because, well, first, I never use it, and second, it's confusing. Besides, if you're UNIX literate, you know all about it already; and if you're not a UNIX-type person, like yours truly, you don't really need it -- Memory Usage Getter, MemoryStick, and other utilities tell you all you need to know and you won't have to memorize or type any arcane commands or interpret any fast-spewing screen text.

Anyway, both Memory Usage Getter and MemoryStick help you figure out when your Mac is slowing down due to lack of RAM, but neither one can tell you how much more RAM you need to install. In fact, as far as I knew until last week, there was no way to determine precisely how much RAM you needed. My advice has always been something like, "you need at least 512MB, and more than that if you keep more than a handful of programs open 24/7 as I do." Then, last week, the June issue of Design Tools Monthly arrived and I had to change my tune. I'll tell you why in a moment but first I want to give a well-deserved plug to Design Tools Monthly, a fabulous newsletter that encapsulates important stories for graphics professionals from magazines and the Web, cramming a whole month of useful design news into 12 densely-packed pages. And, with each issue, you get "the Software Closet," a folder chock full of useful utilities, fonts, artwork, and other goodies.

Anyway, this month one of the Software Closet selections was a little gem called, appropriately enough, "Do I Need More Memory?" (Which will be referred to as DINMM hereafter). It is an application that monitors pageouts on your Mac and then, based on the way you use your Mac, recommends an amount of RAM that will keep you from experiencing pageouts.

Here's what it looks like on my G5 with 2GB of RAM:

And here it is running on a PowerBook that has only 512MB of RAM.

As you can see, this PowerBook would benefit from an additional 256MB of RAM. But, if the past 14 minutes are typical, it doesn't really need more than that.

DINMM has one other great feature you may have noticed in the pictures -- a checkbox that alerts you with a beep whenever a RAM shortage is detected, which is tres cool.

Of course I'd still recommend a 512MB upgrade for the PowerBook above, in spite of what DINMM thinks. Or, put another way, much as I like DINMM I haven't changed my recommendation for most users, which is: In most cases you should install as much RAM as you can afford (within reason -- say up to a gig or two). Why? Well, just as you can never be too rich or too thin, you can never have too much RAM or hard disk space. You might not need it today but someday you probably will.

On the other hand, for those of you on a tight budget, DINMM may very well save you some dough. Either way I suggest trying it and seeing if your Mac might run faster with more RAM.

"Do I Need More Memory?" is free (with a donation requested but not required) from Hillman Minx Software. I just sent him (programmer Paul Johnson) twenty bucks -- he's certainly earned it.