I am looking at adding RAM to my system. I currently use 400mh DDR.
A salesman at the computer store said that I can use higher speed
ram, and the system would simply use it at a slower rate. For
example, he said I can use 533mh RAM and it would only operate at 400mh.
Is this so, it seems wrong to me.
Be extremely skeptical of anything told to you by a salesman in most
computer stores. Most of those people know very little about the
subject, and what they tell you is always suspect. Salesmen generally
make low salaries, and they are hired into those jobs because more
qualified personnel would cost the store a lot more.
What the salesman told you wasn't exactly right, but it was close.
Are you talking about replacing your RAM or adding to what you already
have?
First, the "speed" of the RAM isn't really its speed. It the maximum
speed that it has been tested to run at reliably. So 533mH is the
fastest speed you should run 533mH RAM at.
Second, the speed the RAM actually runs at is the speed the
motherboard is set to run at. If the motherboard is set to run at
400mH, the mixture of 400mH and 533mH RAM will all run at 400mH, and
that's within the tested capability of all your RAM.
But also look at it the other way around. Suppose you had 533mH RAM,
with the motherboard set to run at that speed. If you then added 400mH
RAM, the motherboard would run it all at 533mH. That's not within the
tested speed of all the RAM, and it's likely that (not necessarily
immediately, but at some time in the near future) that the slower RAM
will fail.
Also note that if your plan is to add RAM to what you already have,
it's critical with Windows XP that all the RAM match in all
respects--brand, model, speed, etc. If some of it doesn't match,
Windows is likely to fail.
Finally, how much RAM do you have now, how much are you planning on
having, and why are you planning on changing the amount?
Although many people think that more RAM means better performance,
that is not always true. How much RAM you need for good performance is
*not* a one-size-fits-all situation. You get good performance if the
amount of RAM you have keeps you from using the page file, and that
depends on what apps you run. Most people running a typical range of
business applications find that somewhere around 512MB works well,
others need more. Almost anyone will see poor performance with less
than 256MB. Some people, particularly those doing things like editing
large photographic images, can see a performance boost by adding even
more than 512MB--sometimes much more.
If you are currently using the page file significantly, more memory
will decrease or eliminate that usage, and improve your performance.
If you are not using the page file significantly, more memory will do
nothing for you. Go to
http://billsway.com/notes_public/winxp_tweaks/ and download
WinXP-2K_Pagefile.zip and monitor your pagefile usage. That should
give you a good idea of whether more memory can help, and if so, how
much more.