3.25 GB of RAM instead of 4GB

[Hyraxxx]

On a windows vista x86 system, I put 2x2Gb DDR 2 sticks in the PC. Under My computer, only the odd number of 3.25GB of RAM is being recognized. What usually is the cause of this?

I have another vista x86 system with 2x2 GB DDR sticks and it shows 4GB.

Should I run a memtest on them?

 

[jjmIII]

onboard memory....

 

[sub.mesa]

Yes that is because you run 32-bit, which usually is limited to 2GiB by the way. It can use up to 4GiB, but programs themselves are limited to 2GiB each, though some rare exceptions apply with compile flags.

So bottom line: upgrade to 64-bit OS.

 

[Emulex]

microsoft limits the low end operating systems on purpose. windows 2003EE/2008EE are 32 bit and can rock the full 4gb. there are hacks (painful) to make vista use it all. not recommended.

if you have a reason(compatibility) rock 32 bit - otherwise throw some more ram in that box and rock 64bit.

just got some asus essentio $359 (core2q8300/8gb ddr2) and i5-650/8gb ddr3

hella difference with 8gb and 64bit. there are some compromises for running 64bit - which may not make that .8gb worth it

 

[Hyraxxx]

My vista is reporting 4 GBs. I know about the RAM limit. I am just confused because my 32-bit PC is showing 4GB, while on the new computer I just built, it is recognizing only 3.25 GB.

Whether it is utilizing all 4GB is not of concern for me at the moment.

I have a Mint x64 DVD I can run to verify if it is windows or ram.

Thanks!

 

[BlueWeasel]

Does the computer showing 3.25GB of RAM have the latest Vista SPs and updates?

Seems like an update was released that made Vista report the correct amount, even though not all can be utilized.

 

[postmortemIA]

Does the computer showing 3.25GB of RAM have the latest Vista SPs and updates?

Seems like an update was released that made Vista report the correct amount, even though not all can be utilized.

yep, Vista SP2 will show 4GB, but can use up to 3.25GB.

Get 64-bit OS.

 

[tcsenter]

onboard memory....

This, unless the system reporting 3.25GB has not been patched to Service Pack 1 or later.

 

[corkyg]

yep, Vista SP2 will show 4GB, but can use up to 3.25GB. Get 64-bit OS.

Exactly! See 4 but use 3.5.

 

[tweakboy]

Yes that is true 32 bit can only read up to 3.2GB ,, then came 64 bit technology and it can go as higher and read your sticks all 4GB ,, plus going 64 bit has advantages on performance as well and the OSes 32bit and 64bit have nothing to do with wach other,, way different.

 

[Nothinman]

Yes that is true 32 bit can only read up to 3.2GB ,, then came 64 bit technology and it can go as higher and read your sticks all 4GB ,, plus going 64 bit has advantages on performance as well and the OSes 32bit and 64bit have nothing to do with wach other,, way different.

None of that makes any sense. Any 32-bit OS that fully uses PAE can use up to 64G of physical memory. 64-bit CPUs have existed for over a decade now, it's just that Intel and AMD are just catching up so now MS is too. And the 32-bit and 64-bit releases of software are 99% the same. The main differences are low level startup code and things artificially put there by MS for no real reason that I can see.

 

[Emulex]

some old cards/drivers do not handle PAE >4gb very well. some chipsets also limited this as well. but yeah microsoft did this on purpose half to save more phone calls due to unreliable products back in the days; and to keep their 32bit enterprise edition server premium $$$ price.

i call it b/s.

 

[tcsenter]

Yes that is true 32 bit can only read up to 3.2GB...

No...

http://s89934018.onlinehome.us/images/sysinforam.png

 

[corkyg]

OK - the ubergeeks citing PAE (Physical Address Extension) somewhat obfuscates reality.

http://en.wikipedia.org/wiki/Physical_Address_Extension

Yes - such technology does exist, and Nothinman's opinion as to why it is not used is probably close to the truth. But, reality rules here - what hardware today uses PAE with 32-bit systems?

 

[tcsenter]

Hardware doesn't use PAE (excepting the CPU). OS's do. Modern Windows client SKUs use PAE by default, albeit a neutered form of it.

 

[corkyg]

OK - what is a client Stock Keeping Unit (SKU)? Let me rephrase the basic question. What off-the shelf consumer systems on the market today use PAE? IOW, focus on OP's query. Evidently his system does not have PAE. So, why does HIS system see 3.5 GB out of 4 installed?

 

[postmortemIA]

There's /PAE switch for Windows xp boot loader.
Still, I think it only works for applications that can take advantage of it.
Beside, 32-bit apps can address only up to 2GB of RAM (without PAE awareness). Unless you run 2 of such, you will have hard time using more than 3.25GB.

http://msdn.microsoft.com/en-us/library/ff557168.aspx

 

[Nothinman]

OK - what is a client Stock Keeping Unit (SKU)? Let me rephrase the basic question. What off-the shelf consumer systems on the market today use PAE? IOW, focus on OP's query. Evidently his system does not have PAE. So, why does HIS system see 3.5 GB out of 4 installed?

Virtually every CPU has had PAE support since the Pentium Pro so his system supports it just fine, it's Windows client OSes that don't. If he installed 32-bit Windows Server Enterprise, Linux, FreeBSD, OpenBSD, etc he'd get all of his memory as well.

Still, I think it only works for applications that can take advantage of it.

For AWE, yes, the app needs to be specifically designed to use that. But a 32-bit app can also get up to 3G of VM with the /3GB switch if it's LargeAddressAware bit is set, which can be set on any binary that you want.

And that's per-process, most people have at least a half dozen things running at once so it's very easy to get up to and pass the 4G mark these days even with just 32-bit apps.

 

[corkyg]

"Virtually every CPU has had PAE support since the Pentium Pro so his system supports it just fine, it's Windows client OSes that don't. If he installed 32-bit Windows Server Enterprise, Linux, FreeBSD, OpenBSD, etc he'd get all of his memory as well."

That makes sense. OTH, OP's question is based on a system Vista x86 OS, ergo, it is limited to 3.5 GB of usable RAM.

 

[tcsenter]

Evidently his system does not have PAE. So, why does HIS system see 3.5 GB out of 4 installed?

PAE is not a synonym for 64GB. PAE is a mechanism to extend physical address space, it does not need to actually extend it. IOW, you can implement PAE then cap physical memory support at whatever you want by having the OS simply ignore or truncate anything beyond a particular address limit. 4GB, 6GB, 8GB, whatever.

 

[Emulex]

can you use /USERVA= or /3GB with xp/vista/7 ?

 

[tcsenter]

To clarify, Windows client OS use PAE to support hardware DEP, not to extend physical address space. So yeah, its using PAE mode but its not being used in the traditional sense. The extra bits are being used to contain a descriptor or tag in order to implement DEP and memory protection in hardware.

 

[tcsenter]

can you use /USERVA= or /3GB with xp/vista/7 ?

Yes, but with Vista/7 you have to use BCDedit (or equivalent) and the exact syntax may be a bit different from XP.

 

[Emulex]

is there a reason why folks don't use BCDedit? in 32bit mode you can take away ram from the system and give more to the apps?

i'd rather have 2800meg for an app and 1200 meg pagefille than 2/2?

or does vista/7 already do this?

most 32bit sql server folks tweak the userva and PAE AWE mode. my ancient server uses /3GB with /PAE and /AWE with 10gb of ram in 32 bit mode for sql server. cool as heck to watch it eat up all that ram (you can't watch AWE ram in task mgr windows 2003)

 

[corkyg]

All of this is relatively advanced stuff that the average user/consumer does not get involved with. Go back to OP's basic question and respond. He does not have a "client server," probably does not deal with SQL, and most likely has never heard of BCDedit. Doing Command Line tweaking is not part of the average person's routine. This may help:

http://technet.microsoft.com/en-us/library/cc709667(WS.10).aspx