PC Hardware in a Nutshell, 3rd Edition [Electronic resources] نسخه متنی

5.5 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 when it comes to system performance.
Windows XP runs faster on a slow Celeron with 256 MB than on a fast
Pentium 4 with 64 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.

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.

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

Memory-intensive applicationse.g., Photoshop;
speech/pattern-recognition software; many windows open; multiple
background services; graphics-intensive games such as 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.

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.

As we update this table for each edition, the amount of RAM we recommend keeps growing, both because later releases of the operating systems need more memory and because new versions of applications typically want more memory. Only a couple of years ago, running 512 MB of RAM on a desktop system raised eyebrows, and 1 GB was unheard of except among graphics professionals and others with heavy demands. Nowadays, 512 MB systems are commonplace, and 1 GB systems are not unusual. We remember a time not all that long ago when we were delighted to have 1 GB of disk space .

Each operating system has a "sweet
spot," which 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 adding more than 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; and for the remaining
operating systems, 384 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 1 GB of RAM on his primary Windows 2000 Professional desktop system, and 512 MB on his secondary Windows 2000 Pro systems. Barbara uses 1 GB on her Windows 2000 Pro system. (We don't use Windows XP on any of our production systems.) Our two general-purpose NT 4 servers provide file and print sharing and domain controller functions, and run happily with 128 MB each. Our main Linux server uses 512 MB, and our secondary Linux servers have 256 MB each. Our Linux desktop systems have 384 MB or 512 MB, and all supplementary and test-bed systems have at least 256 MB. Other than our legacy NT4 Server boxes, we no longer have any systems running 128 MB or less.