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Memory Capacity

How much RAM is enough? New motherboards hold 1GB or more. Where is the point of diminishing returns?

Tom Kielick, technology project manager, Baltimore

Depending on what kind of memory your machine takes, an entire gigabyte at today's prices will probably cost you between $100 and $300, so the temptation is to say "fill 'er up." On the other hand, a few bucks is still a few bucks--or big bucks when you're talking about a company full of computers.

To find the answer to your question, we ran our application-based PC WorldBench 4 test suite on five computers with widely varying amounts of memory: 64MB, 128MB, 256MB, 512MB, and 1GB. Two of these computers ran Windows XP Professional, one ran Windows 98 SE, and two ran Windows Me. Some of the faster PCs we tested started with more memory to better mimic common configurations.

Our conclusion: For RAM, 256MB is just about right. But underneath that general advisory, you'll find some interesting data. First and foremost, the speed differences were quite small: For example, when we upgraded a 450-MHz Pentium III Gateway system running Windows 98 from 64MB to 128MB, PC WorldBench 4 ran a mere 3.3 percent faster. A 933-MHz Pentium III Dell PC running Windows Me enjoyed a healthier 6.1 percent increase with the same upgrade, but that's still nothing to write home about. Upgrading these two machines from 128MB to 256MB yielded even paler results (1.6 and 2.3 percent, respectively). And above that? Negligible.

The Windows XP machines were a slightly different story. When upgraded from 96MB to 224MB, our 1.6-GHz Athlon XP+ system from MicronPC squeezed out 8.5 percent better performance. But once again, upgrades beyond 256MB made little difference. PCs with integrated graphics, like the MicronPC Millennia we tested, reserve a certain amount of main memory (32MB in this case) for graphics use. That arrangement decreases the amount of memory available to the OS. If you own a PC with integrated graphics, you should adjust your memory upgrading plans accordingly.

Overall, these tests and others we've conducted show that a memory upgrade improves performance if it reduces a machine's resort to virtual memory (a technique that lets you load more applications and data than you have actual memory for, but uses hard disk reads and writes to accomplish the task). Virtual memory's use of the hard disk slows performance. For PCs with 64MB or less of RAM, just loading the operating system, an application, and some data can call up virtual memory, slowing your system. And that happens even sooner with larger OSs (read XP). Above 64MB, how often your system slows for virtual memory depends on how much you load into your PC (and to a degree, how fast your CPU is; slower PCs see less performance improvement for the same size memory upgrade).

With 128MB of RAM, if you keep opening mail or browser windows--as most of us do these days--you'll start slogging around in virtual memory pretty quickly, especially with a Windows XP system. At just $20 or $30 more than 128MB costs, the added headroom of 256MB pays for itself in productivity--so we'll we stick by our 256MB recommendation.

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