How
much system memory is enough?
A basic rule of
thumb has been you need about three times the amount of memory
than the file size that you are planning to work with. Beyond
this you will probably not see any significant performance
increase and too much memory will actually make your computer
slower. Is that possible you think? I thought that more memory
was always better, right?. The reason excessive memory will
actually make the systems run slower comes in the fact that with
every cycle your CPU must check all the memory addresses. It
checks each address regardless if it is being used or not. If
you have a large amount of memory that is not needed you are
just wasting CPU power on checking empty memory addresses. As
some more astute 3-D gamers may know, currently a 3-D graphics
card with 64MB usually out performs the same graphics card with
128MB.{see How
to choose a graphics card}
A
traditional recommendation has been the optimal amount of system
memory in Megabytes should be the same as the Megahertz of the
CPU. As CPU speeds are now in excess of 3 GHzs this guide may no
longer be optimal. For most of us 512MB will still give us the
optimal performance. Some operating systems such as Windows ME
have serious problems accommodation memory more than 512MB. For
a systems with larger than 512MB of memory it is recommend
running Windows NT, Windows 2000, or Windows XP.
Users that I would recommend going beyond 512MB would be
those who work with large, high resolutions photos, do computer
aided drafting (CAD) and those who would have several large
programs open and running simultaneously. It should also be
noted that the amount of memory is limited by the motherboard.
Even if the specifications on the motherboard say that the board
can accommodate 2 Gigs I would not put more than 1.5 Gigs.
Putting a full two Gigs on the motherboard would be considered
pushing the envelope and can induce instabilities into your
system, especially if low quality memory is used. This
recommendation is even more so if you are planning to over-clock
the computer.
Before
going beyond 512MB of system memory, most people will find a
better performance gain in the speed of the memory vs. adding
more. This is especially true for the Pentium4 as it makes many
more hits to system memory compared to other CPUs.
A system with a P4 and the fastest system memory will
outperform a system with a P4 CPU a grade higher and standard
memory. This is a factor you should consider when trying to get
the best performance for your dollar. The AMD Athlon makes less
system memory hits compared to the Pentium4 and is less
adversely effected by the speed of the system memory.
You
may ask yourself, what is the difference between standard memory
and the fastest memory? To better understand this let us review
a brief history of the different kinds of memory. You may have
known that the early memory was EDO memory 33 Mhz which
progressed to SDRAM 66Mhz, 100Mhz, 133Mhz+, now there is
DDR200Mhz, 333Mhz 400Mhz+. The DDR allows the memory to transfer
data on both the rise and fall of the wave frequency verses only
once per cycle of SDRAM. One aspect that can effect memory
performance more than frequency is that of latency. Latency can
be described as the pause time for the RAM to release the stored
information. This latency comes in two common types: CL2.5 and
CL2.0. The CL2.0 RAM is significantly faster than CL2.5 RAM,
especially when doing real-time 3-D effects. The difference of
the latency is so significant that 333Mhz DDR CL2.0 can
outperform 400Mhz CL2.5 memory in most applications. Having
faster memory can reduce bandwidth limitations and can greatly
increase minimum frames per second in games and video. {see How
to choose a graphics card}
Rambus – a
different kind of system memory, which could possibly be
described as a type of DDR memory at a higher frequency but with
a much longer latency time. As you can see, this will have
different performance effects on different applications.
Sometimes Rambus is faster and sometimes DDR will be faster.
For cost vs.
performance you may find the best performance to cost ratio of
RAM to be the RD2700 (333Mhz) at a CL2.0
Type
Frequency
2400 ~ 200Mhz
2700 ~ 333Mhz
3400
~ 400Mhz
