Hardware Reference
In-Depth Information
The following are minimum memory sizes recommended for use with the most
common PC operating systems over the last 20 years:
Recommended
Operating system
Minimum RAM
RAM (MB)
MS-DOS 3.3
640 KB
4
MS-DOS 5
1 MB
16
Windows 3.1
3 MB
32
Windows 95
8 MB
64
Windows 98
24 MB
128
Windows ME
32 MB
128
Windows 2000 Professional
64 MB
128
Windows 2000 Server
128 MB
256
Windows 2000 Advanced Server
256 MB
512
Windows XP
256 MB
512
It is worth mentioning that adding more memory to a PC can have a
very
significant effect on its performance, particularly if the memory is at, or near,
the minimum recommended for the type of operating system. The reason for
this is that, when insufficient RAM is available the PC's operating system will
create virtual memory on the hard disk which will replace the physical memory
which would otherwise be needed. Unfortunately, writing to and reading from
the hard disk takes significantly longer than performing the same operation to
a semiconductor memory. Frequent accesses to the hard disk impose will cause
a program to run much slower than if the hard disk was not in regular use. To
put this into context, it takes typically less than 200 ns to access physical RAM
and around 10 ms to access a reasonably hard disk drive!
Memory speed
The speed of memory is one of the most important factors in defining the
performance of a system. Furthermore, memory speed forms (or the speed
of memory components) forms an essential part of specification of every PC.
Memory fitted to the PC must comply with this specification and failure to
observe this prerequisite may cause a wide variety of problems including
lock-ups,
re-booting,
and
failure
to
boot.
Some
of
the
most
significant
milestones in the development of memory devices are listed below:
Year first introduced
Memory technology
Access time/speed
1981
DIL RAM
100 ns
1987
FPM RAM
70 ns
1995
EDO RAM
50 ns
1997
SDRAM (PC66)
66 MHz
1998
SDRAM (PC100)
100 MHz
1999
RDRAM
800 MHz
1999/2000
SRAM (PC133)
133 MHz (VCM)
2000
DDR SDRAM
266 MHz
