Total Physical Memory on Task Manager shows wrong value?

[churin]

This is with Vista SP1 installed. I added 2GB RAM making the total
installed RAM size to be 4GB.
My problem is that although BIOS recognize the RAM size to be 4GB and
the Properties/System shows also 4GB, but both of the System
Information/System Tools and Performance/Task Manager show 2GB.

How can I check to see if 4GB is being made available for the system to
utilize?

 

[Jordus]

32 bit or 64 bit vista?


Post Originated from http://www.VistaForums.com Vista Support Forums

 

[churin]

It is 32 bit Vista.

 

[Tim Slattery]

This is with Vista SP1 installed. I added 2GB RAM making the total
installed RAM size to be 4GB.
My problem is that although BIOS recognize the RAM size to be 4GB and
the Properties/System shows also 4GB, but both of the System
Information/System Tools and Performance/Task Manager show 2GB.

How can I check to see if 4GB is being made available for the system to
utilize?

4GB is *not* available to your system. You have a 4GB address space,
but some of that must be used to access BIOS, video RAM, etc. What's
left over is used to access RAM. See
http://members.cox.net/slatteryt/RAM.html

That said, I'd expect you to see more than 2GB. Do you have multiple
fancy video cards, or something else that might include lots of
onboard RAM?

 

[Doug]

How can I check to see if 4GB is being made available for the system to

utilize?

It sounds like the RAM isn't being detected. What does the BIOS show?
Either way, the maximum amount of RAM you will be able to access (without
enabling PAE) is 3.2GB.

 

[Doug]

(oops. "Reply Group")

How can I check to see if 4GB is being made available for the system to
utilize?

It sounds like the RAM isn't being detected. What does the BIOS show?
Either way, the maximum amount of RAM you will be able to access (without
enabling PAE) is 3.2GB.

 

[Colin Barnhorst]

Enabling PAE does not help in 32bit Windows clients, but it does Servers
(Windows Server 2003 Enterprise Editions and later). See the Windows Memory
Limits table for details.
http://msdn.microsoft.com/en-us/library/aa366778.aspx#physical_memory_limits_windows_vista

 

[Ken Blake, MVP]

It sounds like the RAM isn't being detected. What does the BIOS show?

Either way, the maximum amount of RAM you will be able to access (without
enabling PAE) is 3.2GB.

Two points:

1. PAE doesn't help on Windows client operating systems, just on
servers.

2. The maximum accessible amount is not precisely 3.2GB, but varies
from as little as 2 to 2.5 (in rare cases) to as much as 3.5GB,
depending on your hardware configuration. Here's my standard post on
this subject:

All 32-bit versions of Windows (not just XP) have a 4GB address space.
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. The rest of the RAM goes unused because there is no
address space to map it too.

 

[Colin Barnhorst]

There is nothing in Windows itself that limits 32bit Windows from using 4GB
of memory. What limits Windows on modern hardware is the BIOS reserving
memory space for devices. It is called memory-mapped IO and provides a very
rapid but unprotected way of writing data to video cards, etc. The BIOS
reserves the memory space to protect it from the user programs from also
writing there. The whole idea is to get the fastest performace possible out
of things like video cards because that is what users want.

 

[churin]

Two points:

1. PAE doesn't help on Windows client operating systems, just on
servers.

2. The maximum accessible amount is not precisely 3.2GB, but varies
from as little as 2 to 2.5 (in rare cases) to as much as 3.5GB,
depending on your hardware configuration. Here's my standard post on
this subject:

All 32-bit versions of Windows (not just XP) have a 4GB address space.
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. The rest of the RAM goes unused because there is no
address space to map it too.

Does the above mean as follows?

BIOS and System|Properties show correct size of installed RAM while
System Tools|System Information and Task Manager|Performance show the
maximum usable part of the installed RAM. The maximum usable part could
be as low as 2GB. Therefor,if 4GB is installed and Task
Manager|Performance indicates that the Total Physical Memory is 2GB,
then half of the installed RAM is waisted.

 

[Doug]

BIOS and System|Properties show correct size of installed RAM while System

Tools|System Information and Task Manager|Performance show the maximum
usable part of the installed RAM. The maximum usable part could be as low
as 2GB. Therefor,if 4GB is installed and Task Manager|Performance
indicates that the Total Physical Memory is 2GB, then half of the
installed RAM is waisted.

Correct. Your BIOS should tell you how much is detected, your OS how much is
available. (In simple terms)
Fair enough. I just did a quick google to check Windows compatibility with
PAE. I use Unix.
Forgive my absence of a tilde (~)...

 

[Colin Barnhorst]

It's a very big tilde. My XP systems showed anything from 2.2GB to 3.5GB
before all our computers were promoted to Vista.

I use VPC extensively so I just tried an experiment to see how close I could
get to using all the memory in a computer in Windows itself. In VPC I tried
maximizing the memory allocation for an XP Pro vm in its vm Settings. I got
as high as 3.62GB to show on system properties with an allocation of 3.712GB
memory, which is the max VPC allows for a guest, on my Vista Ultimate x64
host. 3.712GB happens to be the max permitted by VPC on any host.

VPC emulates very old hardware so the reservation of relatively little
memory by the guest's BIOS makes a lot of sense. My point is that the
hardware on a computer has everything to do with how much memory is
available to user programs when 4GB of ram is installed.

btw, if VPC had allowed me to allocate a full 4GB for the guest I would
still have only gotten 3.62GB to show on system properties. It is the
addresses that are being reserved.

 

[Colin Barnhorst]

Correction: The last paragraph is not accurate. I made some inquiries with
the virtualization team at MS and I would have seen something closer to but
still under 4GB if VPC supported allocating a full 4GB.

 

[churin]

Correct. Your BIOS should tell you how much is detected, your OS how

Thanks for your clarification. I thought about removing the 2GB stick
for use somewhere else, but that makes the memory access be single
channel(two sticks are being used as dual channel operation) so decided
to leave it in.

 

[Ken Blake, MVP]

Does the above mean as follows?

BIOS and System|Properties show correct size of installed RAM while
System Tools|System Information and Task Manager|Performance show the
maximum usable part of the installed RAM. The maximum usable part could
be as low as 2GB. Therefor,if 4GB is installed and Task
Manager|Performance indicates that the Total Physical Memory is 2GB,
then half of the installed RAM is waisted.

Yes, that's correct. But bear in mind that a usable amount as low as
2GB is very rare. A more typical amount is around 3.1-3.2GB.

 

[Colin Barnhorst]

Ken, I should think that hitting 2GB on the nose with 4GB installed calls
for investigation of the BIOS settings and then testing the hardware. It
just does not sound right to me. The lowest I have ever seen on my own
hardware with 4GB installed is 2.2GB. What do you think?

 

[Ken Blake, MVP]

Ken, I should think that hitting 2GB on the nose with 4GB installed calls
for investigation of the BIOS settings and then testing the hardware. It
just does not sound right to me. The lowest I have ever seen on my own
hardware with 4GB installed is 2.2GB. What do you think?

I agree. Sorry if I seemed to give the opposite opinion. I wasn't
specifically addressing Doug's problem, but rather responding to
churin to correct the somewhat inaccurate statements that "Either way,
the maximum amount of RAM you will be able to access (without enabling
PAE) is 3.2GB."

 

[churin]

Exact number shown on Performance/Task_Manager is 2045 while number
shown while POSTing is 4193216KB. Could you post details of suggested
investigation of the BIOS settings and testing the hardware?

Ken, I should think that hitting 2GB on the nose with 4GB installed
calls for investigation of the BIOS settings and then testing the
hardware. It just does not sound right to me. The lowest I have ever
seen on my own hardware with 4GB installed is 2.2GB. What do you think?