Re: XP SP2 and RAM
Yves Leclerc
>I'm changing motherboards and want to get more RAM, and I currently use WIN
>XP SP2. I was prepared to get 4 1GB pieces but the local technician tells me
>XP SP2 cannot see more than 2-3 GB of RAM, while searching Microsoft tells me
>it can address up to 4GB of RAM. Who is correct?
Microsoft is correct! However, you may need to add a "special" boot flag in
the "boot.ini" in order to tell XP to use 4GB of RAM.
--
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Y.
Jerold Schulman
>I'm changing motherboards and want to get more RAM, and I currently use WIN
>XP SP2. I was prepared to get 4 1GB pieces but the local technician tells me
>XP SP2 cannot see more than 2-3 GB of RAM, while searching Microsoft tells me
>it can address up to 4GB of RAM. Who is correct?
Both.
See http://support.microsoft.com?kbid=291988 A description of the 4 GB RAM Tuning feature and the Physical Address Extension switch
Windows XP Pro will support 4GB of RAM, but iser mode can use a max of 3GB.
Without the /3GB switch, I believe it is 2GB for a user mode process.
Jerold Schulman
Windows Server MVP
JSI, Inc.
http://www.jsiinc.com
http://www.jsifaq.com
Jim
"Rocket Rakoon" <Rocket Rak...@discussions.microsoft.com> wrote in message
news:5B3595FC-BC2F-4229...@microsoft.com...
> I'm changing motherboards and want to get more RAM, and I currently use
> WIN
> XP SP2. I was prepared to get 4 1GB pieces but the local technician tells
> me
> XP SP2 cannot see more than 2-3 GB of RAM, while searching Microsoft tells
> me
> it can address up to 4GB of RAM. Who is correct?
However, the maximum virtual address space for programs is 3GB.
Jim
Dixonian69
Ken Blake, MVP
> I don't know for sure how much that will cost BUT it is not worth the
> money!!
*What* is not worth the money? 2GB? 4GB?
Regardless of what amount of memory you're talking about, you can't judge
from a distance, without knowing what apps the original poster runs, how
much memory is worth the money to *him*. True, for most people running a
common mix of business applications, there is little or no benefit to going
above 512MB or so. But if your apps are memory-intensive enough, more RAM
than that, even *much* more, can make a big difference in performance. For
example, for someone who does a lot of fancy photographic editing of large
images, lots of RAM can be *very* beneficial.
--
Ken Blake - Microsoft MVP Windows: Shell/User
Please reply to the newsgroup
Mak
First re Microsoft: XP-32bit claim: "it can address up to 4GB of RAM" - this
is true, but doesn't really apply to you / help you.
While Windows XP-32bit can address 4GB of RAM as it's actually licensed
(software enforced limits) for up to 4GB of RAM, it will not show you 4GB,
because a lot of space in last gigabyte will be reserved for PCI addresses
(especially SP2, see reasons in this KB
http://support.microsoft.com/default.aspx?scid=kb;en-us;888137).
How much - depends on your motherboard and PCI devices that you have
(motherboard own devices counts too). This whole thing above is really
hardware / crappy drivers limitation, not per se Windows XP fault. But
still, you won't see 4GB of RAM.
Second re technician, if (s)he talks about the above, (s)he's right, the
numbers though: "2-3 GB of RAM" - are a bit off, it's either really crappy
M/B, or worth:
(below this line, there is nothing about physical memory, AKA RAM, it's all
about virtual address space and affect of /3GB switch.)
(s)he's is talking about something completely different, and I'm afraid the
talk is about user mode virtual address space.
32-bit OS can naturally map 4GiB of virtual address space _per_process_. In
NT world (XP is a flavour of NT family), 4GiB is divided into 2 pieces, by
default - 2GiB for user mode and 2GiB is for kernel. So, each, and every
single process _can_ access 2GiB of virtual address space. Right now, I have
on this machine 37 processes running, that gives 37x2=74GiB *potential*
virtual address space plus 2GiB for system (shared) = 76GiB. In reality,
Perfmon (process | virtual bytes | _total) tells me that my machine is using
approximately 1.6GB of virtual address space. This is by far lower than
*potential* I calculated - and this is normal. But the fact is, every
process is guarantied 2GiB.
Now, what /3GB switch does: it splits virtual address space into 3GiB for
user mode and 1GiB for kernel.
Only processes that have LARGEADDRESSAWARE flag on can benefit from this,
non-default split. And there are only few of them, manly specialized
software. Let's say I have 2 applications running that can benefit from
/3GB. The above *potential* calculation would look like this:
35x2+2x3+1=77GiB. (35 processes that can only use 2GiB each, 2 processes
that can use 3GiB and 1GiB (shared) for system).
(again, the above paragraph has nothing to do with RAM, the above numbers
are the same no matter how much or how little RAM you have.Whoever tells you
to use /3GB switch doesn't understand the difference between RAM and virtual
address space).
Third. Warning: few motherboards will automatically/forcefully adjust timing
of your RAM when you install 4GB and won't tell you.
General performance may degrade by few percent. You may be better with 2GB
of RAM than with 4GB if performance is that much important for you and you
don't do excessive multitasking, i.e. interact with a lots and lots of
running applications at once.
"Rocket Rakoon" <Rocket Rak...@discussions.microsoft.com> wrote in message
news:5B3595FC-BC2F-4229...@microsoft.com...
Jonny
Similar was said about 98/98SE/ME and its capability to utilize installed
RAM. Its 512MB out of the box in all cases, 768MB is rare. And MS can't
make up its mind how much these OSes can utilize with mods per 2 different
KB articles.
--
Jonny
Bob I
address space is allocated for the user is the part that completely
confuses the users. ;-)