Why does 2+2=3GB?

[imported_ZeroSignal]

I just installed two OCZ 2GB DDR2 633MHz sticks in my hp6500 series laptop, but it only recognizes 3 GB. With only one stick installed it reads exactly what in should (a little over 2GB) and it reads the same in either slot. I'm pretty sure it's not a problem with the ram sticks, but when they are both installed 2+2=3GB. I was never good at math, but this doesn't seem right.

 

[Riverhound777]

32bit OS doesn't recognize more than 3.25gb memory. do a search...

 

[Cheex]

Originally posted by: Riverhound777
32bit OS doesn't recognize more than 3.25gb memory. do a search...

It depends mainly on how much of the memory addressing space is reserved for your video card.

I have an 8800GTS 320MB and XP shows me using 3.5GB of my 4GB.

 

[imported_Scoop]

Damn, I thought we were going to make it through the week without someone asking this...

 

[Nothinman]

Why does 2+2=3GB?

Because you're running a 32-bit Windows client. Upgrade to Linux (any 32-bit flavor with PAE enabled or a 64-bit one), Windows Server 2003 Enterprise 32-bit or any 64-bit release of Windows (server or client).

 

[n7]

Originally posted by: Scoop
Damn, I thought we were going to make it through the week without someone asking this...

lol not likely.

This'll be the number one n00b question for a long time i suspect, & will likely get worse, much worse

 

[pallejr]

Originally posted by: n7
This'll be the number one n00b question for a long time i suspect, & will likely get worse, much worse

I guess Microsoft has found out as well, since they deal with this issue in SP1 for Vista

 

[n7]

Originally posted by: pallejr

Originally posted by: n7
This'll be the number one n00b question for a long time i suspect, & will likely get worse, much worse

I guess Microsoft has found out as well, since they deal with this issue in SP1 for Vista

Yeah, but the way they "deal" with it is very misleading, since 99% of people will think they have a full 4 GB successfully working, since they'll never think to check task manager for the real story...

 

[AmberClad]

Originally posted by: Cheex

Originally posted by: Riverhound777
32bit OS doesn't recognize more than 3.25gb memory. do a search...

It depends mainly on how much of the memory addressing space is reserved for your video card.

I have an 8800GTS 320MB and XP shows me using 3.5GB of my 4GB.

Yeah, it really seems to vary from system to system. If I boot into XP, I only see 3.4GB of my 6GB, despite having the same 320GB video card as you.

 

[DanDaManJC]

yeah i have vista 32bit + a mobile ati x1600, 128mb memory onboard + hypermemory, and vista recognized 3gb out of the 4gb i had installed. no complaints though, 3 worked just fine too alt - tabbing outta crysis was a breeze, even if the laptop couldn't otherwise play the game xD

 

[Mem]

Originally posted by: n7

Originally posted by: pallejr

Originally posted by: n7
This'll be the number one n00b question for a long time i suspect, & will likely get worse, much worse

I guess Microsoft has found out as well, since they deal with this issue in SP1 for Vista

Yeah, but the way they "deal" with it is very misleading, since 99% of people will think they have a full 4 GB successfully working, since they'll never think to check task manager for the real story...

I think the main reason for that is to cut down on support calls from OEM companies like DELL etc..,anyway SP1 won't change much ram wise just state the 4GB ,but in the real world it'll still have less then 4GB available and also still be limited to the memory restrictions that Vista x68(32 bit OS) has.

I guess it'll keep some of them happy .

 

[n7]

Oh that i know, i just kinda dislike this, since rather than force knowledge on people, they're bandaiding it so knowledge won't be gained...

 

[BlueAcolyte]

Didn't Microsoft intentionally handicap Windows XP and Vista-32bit? Since Linux, Server 2003 are able to overcome this limitation.

Also, on the supreme commander forums, someone made a fix that lets an application address more than 2GB of RAM in Windows XP.

 

[pallejr]

Originally posted by: BlueAcolyte
Didn't Microsoft intentionally handicap Windows XP and Vista-32bit? Since Linux, Server 2003 are able to overcome this limitation.

Also, on the supreme commander forums, someone made a fix that lets an application address more than 2GB of RAM in Windows XP.

Yes, they crippled XP in SP2.

That fix can be made by using the /3GB switch in boot.ini and editbin (if the app is not ready for it). But for various reasons that can lead to strange things

 

[Mark R]

Originally posted by: BlueAcolyte
Didn't Microsoft intentionally handicap Windows XP and Vista-32bit? Since Linux, Server 2003 are able to overcome this limitation.

Also, on the supreme commander forums, someone made a fix that lets an application address more than 2GB of RAM in Windows XP.

It's not so much an intentional 'crippling' of the OS, as an attempt to improve reliability.

WHen 32 bit systems were first developed by Intel, there was a hard, theoretical limit of 4 GB.

However, the most recent systems have various 'hacks' (PAE) to get around the 4 GB limit. Without PAE, the system can only see 4GB of memory (and that includes the memory on graphics cards, and the control functions in various other peripherals like hard drives, sound, LAN, etc.)

With PAE, the system divides the memory up into 4 GB blocks, and the OS can then select a block to be used at a particular time. This is slow, but more importantly, software that interacts with the OS (drivers), has to be able to cope with the fact that there are different blocks of memory that theOS can select.

With Windows 2k3 server being a server OS, there are going to be relatively few hardware setups and relatively few drivers - additionally, most customers running 2k3 are going to be using fully approved drivers, etc.

With XP, where there are lots of drivers out in the 'wild' and lots of bottom feeder manufacturers who will ship the first driver that looks like it might work - then this is a big problem. Installing 'standard' XP drivers on a system with more than 4 GB, would almost certainly lead to frequent, 'random' BSODs.

Not unreasonably, MS made the decision, not to support PAE on their 'home' OS. Users who actually need 4 GB +, are most likely to be business or power users, who will use a more appropriate OS.

 

[pallejr]

PAE is not a hack. It is just a change to the page table. The address space is flat (no dividing, no "swapping"), and is 64 GB or more, depending on the CPU.

 

[Nothinman]

That fix can be made by using the /3GB switch in boot.ini and editbin (if the app is not ready for it). But for various reasons that can lead to strange things

No, that changes the VM layout and has no affect on the amount of physical memory that the OS can address.

It's not so much an intentional 'crippling' of the OS, as an attempt to improve reliability.

It most definitely was a crippling, but yes the intention was to improve stability in the presence of poorly written drivers.

With PAE, the system divides the memory up into 4 GB blocks, and the OS can then select a block to be used at a particular time. This is slow, but more importantly, software that interacts with the OS (drivers), has to be able to cope with the fact that there are different blocks of memory that theOS can select.

All that happens with PAE is that another level of page tables is added and the memory addressing goes from 32-bit to 36-bit. You seem to be think about AWE which is the userland API MS created so that processes can address more than their 2G of VM.

PAE doesn't affect userland processes at all, even with PAE enabled they still only get 4G of VM with 2G dedicated to the kernel (1G if you use the /3GB boot.ini switch) since they only ever see virtual addresses.

Not unreasonably, MS made the decision, not to support PAE on their 'home' OS. Users who actually need 4 GB +, are most likely to be business or power users, who will use a more appropriate OS.

By that definition it was unreasonable since most business and power users will be using the workstation version of their OS, i.e. XP Pro, which is the OS they decided to cripple.

 

[pallejr]

Originally posted by: Nothinman

That fix can be made by using the /3GB switch in boot.ini and editbin (if the app is not ready for it). But for various reasons that can lead to strange things

No, that changes the VM layout and has no affect on the amount of physical memory that the OS can address.

That was a reply to:

Also, on the supreme commander forums, someone made a fix that lets an application address more than 2GB of RAM in Windows XP.

Which definitely has something to do with the layout of the virtual address space

 

[Nothinman]

Which definitely has something to do with the layout of the virtual address space

Yes, which is what the /3GB switch does. But the only processes allowed to address the 3G of VM with the switch are those that are marked large address aware, I'm not sure if SupCom is marked large address aware out of the box but if not that's probably the fix that the other poster was talking about.

 

[pallejr]

And that "fix" can be done with the tool i mentioned, editbin.

 

[kreacher]

I've got an even weirder problem. Windows XP SP2 is showing the RAM on my system as 2.0GB when I've got 4GB installed. The BIOS is showing 4GB (I've enabled memory remapping and updated the BIOS) and CPU-Z is showing 4GB. The 'My Computer' properties say that Physical Address Extension is enabled and the boot.ini file has the NOEXECUTE=OPTIN parameter (Core 2 Duo CPU with Execute Disable enabled).
Anyone know why I can't see even 3.x GB of RAM?

 

[Nothinman]

Anyone know why I can't see even 3.x GB of RAM?

Because you have enough hardware that 2G worth of addresses are stolen?

The amount of memory that you see isn't arbitrary, it's determined by your hardware.

 

[kreacher]

I was thinking the same thing but apparently its an issue with Asus motherboards -
The root cause of this is due to one of the limitations of 32-bit Windows XP.
When the memory remap option has been enabled in BIOS, the occupied memory address will then be remapped to addressable spaces above 4G.
Apart from that, as memory remap function has been implemented based on 1G block unit, the available memory space between 2~4GB will then be remapped to spaces 4G.
However, as 32-bit OS does not recognize anything above 4G, consequently, the remapped 2GB will be lost, hence reduces the available memory space down to 2GB.
Due to this reason, it is highly recommended to disable memory remapping option when using 32bit OS.
EDIT: So I can either disable memory remapping and use 2.93 GB RAM in XP or enable it and upgrade to a 64-bit OS to use the full 4GB.

 

[imported_BikeDude]

Originally posted by: Mark R
With XP, where there are lots of drivers out in the 'wild' and lots of bottom feeder manufacturers who will ship the first driver that looks like it might work - then this is a big problem. Installing 'standard' XP drivers on a system with more than 4 GB, would almost certainly lead to frequent, 'random' BSODs.

My pet peeve: nVidia drivers after version 79.11 either crash (BSOD), freeze or refuse to allow direct-x titles run. 79.11 worked, but not any of the newer ones. I haven't tested the very latest versions, so I guess they could've fixed it by now (not likely though). Their release notes reveal that PAE support was added around 5x.xx, but they seem to have stopped testing PAE some time after 79.11.

So it is quite reasonable of MS to drop PAE support for XP/Vista. It makes more sense to use a 64-bit OS at this point anyway.

 

[Nothinman]

Apart from that, as memory remap function has been implemented based on 1G block unit, the available memory space between 2~4GB will then be remapped to spaces 4G.

Ah, that's pretty ugly and mildly entertaining at the same time.

So it is quite reasonable of MS to drop PAE support for XP/Vista. It makes more sense to use a 64-bit OS at this point anyway.

That's some backwards logic. It's more reasonable for nVidia to fix their drivers than it is for MS to remove a feature because driver writers can't be troubled to test their code.