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.

Light

Web browsing, email, casual word processing and spreadsheets, checkbook management, and simple games; one or two windows open; particularly if using software one or two versions behind current releases.

Typical

Applications listed above, particularly current versions; three to five windows open; using more demanding applications, including casual database updates and queries, complex spreadsheets, light/moderate programming, mainstream games. File and print sharing in small workgroups or home networks.

Heavy

Memory-intensive applications, e.g., Photoshop; speech/pattern-recognition software; many windows open; multiple background services; graphics-intensive games like Quake III; heavy programming, especially with an Integrated Development Environment (IDE) and doing frequent compiles and links; file and print sharing for large workgroups or departmental groups. Limited use as an application or database server.

Extreme

Professional scientific, engineering, and statistical applications; manipulating very large data sets; use as a consolidated file, print, application, and database server.

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.

Table 5-1. Recommended memory by operating system and usage pattern

Operating system	Light	Typical	Heavy	Extreme
Windows 95	24 MB	64 MB	128 MB	N/R
Windows 98/98SE	32 MB	64 MB	128 MB	N/R
Windows Me	64 MB	64 MB	128 MB	N/R
Windows NT 4 Workstation	64 MB	128 MB	256 MB	384+ MB
Windows NT 4 Server	96 MB	256 MB	512 MB	768+ MB
Windows 2000 Professional	96 MB	192 MB	384 MB	512+ MB
Windows 2000 Server	128 MB	256 MB	512 MB	768+ MB
Windows XP Home/Professional	128 MB	256 MB	512 MB	1,024+ MB
Windows XP Server	256 MB	384 MB	768 MB	1,024+ MB
Linux (GUI workstation)	96 MB	128 MB	256 MB	384+ MB
Linux (text-based server)	64 MB	96 MB	192 MB	256+ MB

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.

If you're wondering whether we practice what we preach, Robert uses 256 MB of RAM on his NT 4 Workstation systems, and 384 MB or 512 MB of RAM on his Windows 2000 Pro systems. Barbara uses 256 MB on her Windows 2000 Pro system. Our two general-purpose NT 4 servers provide file/print sharing and domain controller functions, and run happily with 128 MB each. Our main Linux server uses 256 MB, and our secondary Linux servers have 128 or 192 MB each. Our Linux desktop systems have 512 MB each, and all supplementary and test-bed systems have at least 128 MB. We no longer have any systems running 64 MB or less.