5.4 How Much Memory Is Enough?
Back when memory cost $50 per megabyte, we advised people to install as much memory as they could afford. With memory now selling for pennies per megabyte, we advise people to install as much memory as their motherboards will accept.
How much memory you actually need depends on the operating system and applications you use, how many windows you keep open, which background services and processes you run, and so on. Memory is more important than processor speed to system performance. Windows XP runs faster on a slow Celeron with 128 MB than on a fast Pentium 4 with 32 MB.
Using a big swap/paging file cannot substitute for having enough RAM. Windows virtual memory allows you to run more and larger programs than fit into physical memory by temporarily swapping data from RAM to a disk file. When Windows swaps to disk, performance takes a major hit. If your hard disk clatters away every time you switch between running applications, that's a sure sign that heavy paging is going on and that your system needs more memory. RAM is cheap. Install enough of it to minimize use of the paging file.
To determine how much memory you need, choose the following category that best describes your usage pattern. If you fall between two, choose the higher. Note that newer versions of applications usually require more memory.
Table 5-1 lists the minimum amount of memory we recommend by operating system and usage. These are ad hoc rules based on our experience, so your mileage may vary. More is always better, because using more than the recommended minimum contributes to system stability. Windows 9X is of questionable robustness for Heavy usage, let alone Extreme usage, so we do not provide recommendations for Windows 9X in Extreme usage.
Each operating system has a "sweet spot" that depends on the application mix, but is typically about midway between our recommendations for Typical and Heavy usage. Adding memory increases performance until you reach the sweet spot, but beyond that results in decreasing returns. We generally find the sweet spot for Windows 95/98/Me to be 96 MB; for Windows NT Workstation 4.0, 192 MB; for Windows NT Server 4.0, 384 MB; for Windows 2000 Professional, 256 MB; for Windows 2000 Server, 384 MB; for Windows XP (Home and Professional Editions), 384 MB; for Windows XP Server, 512 MB; for recent Linux releases used as a GUI workstation, 192 MB; and for Linux used in text-mode as a server, 128 MB. Your mileage may vary.
In general, the best way to determine if you've reached the sweet spot for your own mix of applications and your personal working style is to keep an eye on how frequently the system pages out to the hard disk. If that happens frequently, you need more memory. If your system pages only occasionally, you probably have enough memory. Our rule is simple. If in doubt, always err on the side of having more memory rather than less.