/3GB Switch

[Jeff]

In using an application that is a real memory hog
(ANSYS), I've had to introduce myself to the /3GB boot
switch. I'm using XP SP1, patched with the upgrade that
makes the /3GB feature bootable with this OS. Couple of
questions:

1.) The system reports I have four processors installed,
not the 2 I actually have.

2.) My Computer->Properties only reports the presence of
3GB of RAM, not the four that is installed. The BIOS sees
all four, however.

3.) What is a good source for documentation on the /3GB
switch? Information seems to be sparse.

Thanks,
Jeff

 

[David Robbins]

In using an application that is a real memory hog
(ANSYS), I've had to introduce myself to the /3GB boot
switch. I'm using XP SP1, patched with the upgrade that
makes the /3GB feature bootable with this OS. Couple of
questions:

1.) The system reports I have four processors installed,
not the 2 I actually have.

are they two hyperthreaded cpu's? if so each one will show up as two in the
task manager display.

2.) My Computer->Properties only reports the presence of
3GB of RAM, not the four that is installed. The BIOS sees
all four, however.

3.) What is a good source for documentation on the /3GB
switch? Information seems to be sparse.

have you searched for "/3gb" at support.microsoft.com? got 25 hits there
with all sorts of stuff about it. including at least one article that says
something about wrong memory count being reported in some cases.... didn't
read them all, just enough to see what you were asking about, but there
seems to be some info there that may be interesting... maybe start with this
one: http://support.microsoft.com/default.aspx?scid=kb;en-us;316739

 

[Guest]

Thanks for your response. When you limit the search to
WinXP, you get six responses, none of which address the
memory question. I should have mentioned that was where I
went first. (One of the articles did help with a
different problem though - THANKS)

Also thanks for info re hyperthreading.

Still leaves the question re why only 3GB shown, and is
it a problem or just an anomoly.

 

[Jim H]

The processors are probably hyper-threaded and appear as 4 in task manager.

Are you sure XP can address that much physical RAM? I know it can address
that and more as virtual mem, but I'm not sure about physical.

I only ask because Win2003Server standard edition is limitted to 4GB of RAM.
Win2003 Server Web edition is limitted to 2.

Is running a server OS out of the question?


I just found this on the web:
http://www.tek-tips.com/gviewthread.cfm/lev2/67/lev3/70/pid/779/qid/756119

<snip>
Finally we find that in fac was a SO limitation.
By default Windows XP/2k/NT set a limit for the maximum alocated memory per
process - 2G.


On Win XP_Pro/2k we can increase taht limit, maximum 3G.
all you have to do is to add a "/3GB" switch in your boot.ini file (off
course you have to have the admin rights).

</snip>

Good luck,
jim

 

[Alex Nichol]

1.) The system reports I have four processors installed,
not the 2 I actually have.

Are these recent Pentiums with Hyperthreading? These are seen as two
processors each

2.) My Computer->Properties only reports the presence of
3GB of RAM, not the four that is installed. The BIOS sees
all four, however.

The point of the /3GB is to take only 1G rather than 2 for system
address space: I *expect* this is confusing the Properties display

3.) What is a good source for documentation on the /3GB
switch? Information seems to be sparse.

If you find one, let me know

 

[jeff]

MS does have some info on support.microsoft.com. On my
machine, setting the 3GB switch caused a blue screen on
boot. MS has a patch for this, referenced on their sight,
but you have to call them for it.

One of my problems is a driver for a 256 MB 3dlabs video
card that won't load with the switch after I added a raid
card. MS has an article on this, but I haven't
implemented it yet. (See userva switch).

If I find anything else, I'll pass it on. Incidently,
3dlabs was pretty unhelpful in addressing my problem,
saying "oh, we've heard of that, but we've never seen
it." I thought that was a little crummy.

Thanks to all,
Jeff