XP Pro RAM

[Kernel]

If XP can only use 3 GB of RAM, could I install two 2 GB sticks and just let
it choose? The reason being is I'm going to build a new PC and it appears
that 4 GB may be cheaper/easier to find that one 2 GB and one 1 GB.

TIA.

 

[John John - MVP]

If XP can only use 3 GB of RAM, could I install two 2 GB sticks and just let
it choose? The reason being is I'm going to build a new PC and it appears
that 4 GB may be cheaper/easier to find that one 2 GB and one 1 GB.

Sure, no problem at all. Install 4GB and the OS will use what it can,
the rest will just go unused but it won't cause any problems.

John

 

[Kernel]

Thanks for the speedy answer. Now I'm off shopping for some parts...

 

[John John - MVP]

You're welcome, have fun shopping.

John

Thanks for the speedy answer. Now I'm off shopping for some parts...

 

[Ken Blake, MVP]

If XP can only use 3 GB of RAM, could I install two 2 GB sticks and just let
it choose? The reason being is I'm going to build a new PC and it appears
that 4 GB may be cheaper/easier to find that one 2 GB and one 1 GB.

Yes, that's no problem.

But bear in mind that "XP can only use 3 GB of RAM" is not completely
accurate. Here's the correct info:

All 32-bit client versions of Windows (not just Vista/XP/7) have a 4GB
address space (64-bit versions can use much more). That's the
theoretical upper limit beyond which you can not go.

But you can't use the entire 4GB of address space. Even though you
have a 4GB address space, you can only use *around* 3.1GB of RAM.
That's because some of that space is used by hardware and is not
available to the operating system and applications. The amount you can
use varies, depending on what hardware you have installed, but can
range from as little as 2GB to as much as 3.5GB. It's usually around
3.1GB.

Note that the hardware is using the address *space*, not the actual
RAM itself. If you have a greater amount of RAM, the rest of the RAM
goes unused because there is no address space to map it to.

 

[Twayne]

In
Ken is right; you should have no problems. In fact, depending on the mobo
and setup, you might not even be able to use a 2 + 1 GB mix of RAM modules.
Many systems require them to be inserted in pairs, and then go even farther
and insist that they be the same size for each module in the pair, so a 2 +
1 might be disallowed anyway
..
Further, if say, you have 4 memory slots and two 2Gig modules, the
modules may be requied to occuply slots 0 and 2 only. Or slot 0 only if a 4
GB module is allowed; often they are not. Slot 0 must always be occupied.

It sounds a lot worse in words than it really is. All it really means is,
be sure to read the documentation that explains how RAM expansion is
accomplished for your specific mobo if you aren't already certain. For
instance on my Dell T3400 I cannot use any RAM module greater than 2 GB
each. If there is to be more than one RAM module, they must be installed in
pairs 0, 2 and then 1,3, plus each module of each pair must be the same
size.
They can vary in speed capabilities, but the entire RAM complement will
run at the slowest speed of the slowest module in the set/s.

The

Yes, that's no problem.

But bear in mind that "XP can only use 3 GB of RAM" is not
completely accurate. Here's the correct info:

It's completely accurate enough for the purpose of the querant and all
you've really done here is provided information that could "confuse the
issue with facts".

All 32-bit client versions of Windows (not just Vista/XP/7)
have a 4GB address space (64-bit versions can use much
more). That's the theoretical upper limit beyond which you
can not go.

"Theoretical"?? Hardly. 4 GB or however you want to count it, is EXACTLY
the number of address spaces available. It's not theoretic; it's very real
and the laws of physics makes sure it remains that way.

But you can't use the entire 4GB of address space.

Wrong: You CAN and DO use the entire 4 GB of address space. There is no
"wasted" RAM, this time in theory, because some addresses, though they
exist, may never be used in every machine although they are still assigned,
and there are a few used for software setups too, plus some of the BIOS
needs.

Even

though you have a 4GB address space, you can only use
*around* 3.1GB of RAM. That's because some of that space is
used by hardware and is not available to the operating
system and applications.

Hardware is NOT the only address sets that are assigned by the system when
it starts up.

The amount you can use varies, but is more likely to be in the 3.2 to 3.7
area for most retail machines sold today.

It isn't the "amount you can use", it's the amount that is LEFT available.
Unless you do something silly, you WILL use it, not "can" use it.

depending on what hardware you have installed, but can
range from as little as 2GB to as much as 3.5GB. It's
usually around
3.1GB.

Very, very few people, if any, will ever see 2 Gig used by system hardware
on a standard XP desktop machine. 2 GB however is often considered the
"sweet spot" or "point where diminishing returns" will soon occur.

More accurately stated, the system first assigns the system addresses from
the top of the 4 GB of address space downward. Since an address cannot be
used twice, those addresses are NOT available any longer to be used for
anything else. Whatever is left after this assignment set is completed is
what you can have for actual Random Access Memory addressing.
If you find you only have 2 GB of RAM available when you install 4,
you're either not here asking these questions because you already know more
than most people here, OR more likely you have a physical problem with your
hardware. RAM or its support cktry has a problem, is mismatched, mis-setup,
or some other hardware issue is going on. In fact, if you see less than 3 GB
available when you have 4 installed, you should still make certain you know
why or you probably wouldn't be the type of person who would need this
newsgroup.

Note that the hardware is using the address *space*, not

No, it's using the "ADDRESS", of which there are 4GB of separately
addressable locations in the RAM modules.

the actual RAM itself. If you have a greater amount of RAM,
the rest of the RAM goes unused because there is no address
space to map it to.

More accurately, the addresses are already used and thus cannot be used to
address anything else.

And we won't even think of discussing RAM Extenders to go beyond 4 GB on an
XP machine although they are available as specialty setups.

If you're going to try to explain things, at least try to be accurate about
them. I'm no expert or technical writer, but your post gave me a couple of
completely errant pieces of advice.

HTH,

Twayne`

 

[VanguardLH]

John John wrote ...


Thanks for the speedy answer. Now I'm off shopping for some
parts...

Plus you're likely to retain the dual-channel feature of your memory if
you use matching RAM modules. You lose dual-channel (if your mobo has
it and it is enabled) if you mix a 2GB module with a 1GB module.

From Newegg but without any details of your hardware so I looked up
240-pin DDR2 1066 memory (same Geil brand for all):

4GB (2 x 2GB): $110
http://www.newegg.com/Product/Product.aspx?Item=N82E16820144213

2GB (1 x 2GB): $57
http://www.newegg.com/Product/Product.aspx?Item=N82E16820144359
1GB (1 x 1GB): $30
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231143

So 4GB (2 x 2GB) was $110 while 3GB (1 X 2GB + 1 x 1GB) was $87. Yes,
you would save $23 but you would lose any dual-channel feature. Whether
dual-channel is important depends on if you are currently hitting your
max physical memory. In benchmarks (and not in real use), dual-channel
gives you all of about 7% performance increase, if that. If you're
running out of physical memory, you'll get far more speed increase by
having more memory than for the loss of dual-channel. So 2GB+1GB could
end up boosting the speed of your host even with the loss of dual-
channel mode; however, 2GB+2GB would also give you the speed boost while
retaining dual-channel mode.

http://en.wikipedia.org/wiki/Dual-channel_architecture

Of course, when you later move to a 64-bit OS then you can make use of
that other 1GB of memory. Meanwhile, you could try to use some OS
tweaks, like the one that keeps more of the OS kernel in memory; see:

http://msdn.microsoft.com/en-us/library/ee377084(BTS.10).aspx
http://support.microsoft.com/kb/184419

about DisablePaging Executive. Warning: some drivers actually expect to
get paged out and will fail (crash) if not allowed to do so.

You could also play with the /3GB boot.ini option. The /3GB switch
gives more memory to user process space (i.e., your apps) but is useless
unless those user apps use the IMAGE_FILE_LARGE_ADDRESS_AWARE in the
process header. You probably don't have have any apps that can access
more than 2GB of memory.

http://www.microsoft.com/whdc/system/platform/server/pae/paemem.mspx
http://support.microsoft.com/kb/291988

Have you actually read the manual for your mobo to determine what memory
configurations it will allow?

 

[Kernel]

Thanks. I'm planning on building a new system, Gigabyte AM3 to get SATA 3
and USB 3. But for now I'll be using an extra copy of XP Pro that I have
laying around, hence the 3G RAM question. I'll use two 2 GBs for now then
add more when I upgrade OS.

 

[Ken Blake, MVP]

Thanks.

You're welcome. Glad to help.

I'm planning on building a new system, Gigabyte AM3 to get SATA 3
and USB 3. But for now I'll be using an extra copy of XP Pro that I have
laying around, hence the 3G RAM question. I'll use two 2 GBs for now then
add more when I upgrade OS.

Just one more point: 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
significantly, and that depends on what apps you run. Most people
running a typical range of business applications under XP find that
somewhere around 512MB works well, others need more. Almost anyone
will see poor performance with less than 256MB, but few people need as
much as 3GB. 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.

 

[Kernel]

I'd also like to thank all of the MVPs, and the other guru's, who have
helped soooo many people over the years. I've used the Google Advanced
Search with this NG a zillion times, and always found the answer. In fact I
found a lot of answers and developed a long list of tips that I've saved.
Mr. Ken Blake, and God Rest His Soul Alex Nichol are only two of the
standouts; everyone was always ready to help, even ol' Alias. I don't mean
to try and rank the talent, you are all 'farmers' (a farmer is a person who
is outstanding in his field).

The forums will never be as easy to use, to search, and to get good help as
this service.

Thank you all.

Thanks.

You're welcome. Glad to help.

I'm planning on building a new system, Gigabyte AM3 to get SATA 3
and USB 3. But for now I'll be using an extra copy of XP Pro that I have
laying around, hence the 3G RAM question. I'll use two 2 GBs for now
then
add more when I upgrade OS.

Just one more point: 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
significantly, and that depends on what apps you run. Most people
running a typical range of business applications under XP find that
somewhere around 512MB works well, others need more. Almost anyone
will see poor performance with less than 256MB, but few people need as
much as 3GB. 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.

 

[Ken Blake, MVP]

I'd also like to thank all of the MVPs, and the other guru's, who have
helped soooo many people over the years. I've used the Google Advanced
Search with this NG a zillion times, and always found the answer. In fact I
found a lot of answers and developed a long list of tips that I've saved.
Mr. Ken Blake, and God Rest His Soul Alex Nichol are only two of the
standouts;

You're welcome, and thank you very much for such kind words. I'm not
sure I deserve it, but it's a great honor to be ranked with Alex
Nichol, who was one of my newsgroup heroes.