Max RAM for Windows XP/Vista?

[SPARTAN-117]

In lue of the soon to be launch of Windows Vista, one must wonder how much RAM this puppy will be able to take? Also, for those of us with older systems, how much RAM can Windows XP handle?

Well having been unable to find any sold data for the max RAM supported by Windows XP, I'm guessing that it maxes out at 4-8gb depending on which mobo you use. I would like to see where you all hit the firewall in this aspect.

As for Vista, well accorrding to Wikipedia, it'll take upto 128gb of RAM ( http://en.wikipedia.org/wiki/Windows_Vista ).

The reason for writing this is that I spent (and am sure quiet a few others like me did) $2500 on my first PC build 3 months ago and am not wanting to go through the whole process again in just a few weeks. I'm wondering if just plugging in an extra 2gb of RAM on my system will help stay off a huge upgrade?

Any and all advice/comments appreciated.

 

[mad-dog]

Windows supports 3gig's of RAM, Vista requires 750MB to run the desktop so 2gig's minimum is recommended to run programs, I've heard that Vista is capable of supporting 8gig's of RAM.. 8O

 

[SPARTAN-117]

I've got a friend running 4gb of Corsair XMS Dominator DDR-400 RAM in his Windows XP box. I thought 2gb was pushing it because I've not been able to find out where it maxes out.

If Vista truely is able to sport 128gb of RAM then we need much larger mobo's.

 

[mad-dog]

I've got a friend running 4gb of Corsair XMS Dominator DDR-400 RAM in his Windows XP box.

Yes, but the OS only uses 3GB...

I thought 2gb was pushing it because I've not been able to find out where it maxes out.

You can install 4GB but the OS simply ignores 1GB of RAM

If Vista truely is able to sport 128gb of RAM then we need much larger mobo's.

Where did you come up with 128GB of RAM, i said 8GB before... :?
I can envision motherboards stacked up like a parking garage 16 high to hold 128GB of RAM....lol

 

[okie]

Yes, but the OS only uses 3GB...
You can install 4GB but the OS simply ignores 1GB of RAM

That's not true.

Windows 2000 and 32-bit XP allocates 2GB for user-mode processes, and 2GB to kernel-mode processes. This allocation only becomes a problem when you start using close to 2GB of RAM. If you get close to that, you can put the /3GB switch in your BOOT.INI. That will change your allocation to 3GB/1GB user/kernel.

Regardless, some space in the range from 3GB to 4GB is mapped for access to your PCI/PCI-X/PCI-Express cards.

PAE on 2000 and 32-bit XP increases your addressable memory to 36 bits, or 64GB (16GB on older implementations). This is a memory window hack (like EMS in the DOS days) implemented in Xeons and Opterons. This goes into the BOOT.INI as well.

In 32-bit land, you can go with NUMA for large memory access. NUMA works in 64-bit as well, but 64-bit doesn't really have the same adressing limitations. Even 32-bit apps running on 64-bit benefit, as EACH PROCESS has access to its own 32-bit address space - that's 4GB per program. Not too shabby, in other words.

Two of my machines have over 4GB of RAM (one has 8GB, and the other 12GB)... they're both servers. My desktops have between 512MB and 2GB each. FWIW, I can run Vista (32-bit) fine on 1GB with Visual Studio, and tons of other programs running. 64-bit Vista seems to want more like 2GB in my experience. I can't comment on gaming requirements, though.

Just for giggles, new 64-bit Windows versions support a minimum of 16TB (yes, terabytes), with a 8TB/8TG user/kernel split. Each app has a 128GB address pool.

Cheers

 

[mad-dog]

ok, well i was 1/2 right ....lol

 

[okie]

Heh...

Well people at home using 32-bit XP shouldn't really need more than 2GB anyway. The software I write for work, however, is dependent on accessing tons of memory...

... that's the only reason I was able to bore everyone with the post above :roll:

 

[mad-dog]

Nothing boring about that knowledge man, that's good stuff and i love to learn from people that are more knowledgeable than me....thanx 4 sharing
"my name is mad-dog and i am a addict"

 

[SPARTAN-117]

If Vista truely is able to sport 128gb of RAM then we need much larger mobo's.

Where did you come up with 128GB of RAM, i said 8GB before... :?
I can envision motherboards stacked up like a parking garage 16 high to hold 128GB of RAM....lol

That bit of info came from the Wikipedia link I listed. According to that article, all versions of Vista above Bussiness grade will be able to sport 128gb of RAM.

 

[okie]

I'm not sure who contributed the info in Wiki, but I got my info from my MSDN dev docs...

I'm inclined to believe that the 128GB listed at Wiki refers to the pool size limit (which is 128GB). The overall limit is still 17TB (8TB user/8TB kernel/1TB system cache).

 

[yuppie]

Windows XP Pro can use up to 4GB of RAM, but when you first install all of it you will only see 3 GB. this is caused by one or both of the following;
1. There is a BIOS setting that uses a portion of the RAM ans a temp file backup solution, which can be disabled in the BIOS.
2. Add the /PAE switch to the boot.ini file, this will access the full 4GB, but will limit 2GB to the OS and 2GB to other programs. If you add the /3GB switch after the /PAE it will allocate 1GB RAM to the OS, and 3GB to all other apps.

 

[Cypherdude]

From I've been reading at Wiki
http://en.wikipedia.org/wiki/Physical_Address_Extension#Windows
"desktop versions of Windows (Windows XP, Windows Vista) limit physical address space to 4 GB for driver compatibility reasons" even if the PAE switch in BOOT.INI is enabled.

Do you actually have any machines running a 32-bit XP Pro or 32-bit Vista with over 4 GB which recognize all your RAM? I think perhaps your MSDN dev docs might be mistaken.

Here is the most current official MSDN dev document "Memory Limits for Windows Releases":
http://msdn.microsoft.com/en-us/library/aa366778(printer).aspx
It's the printable version so you'll get a Print Dialog pop-up. Click on the O/S at the beginning of the doc you wish to research. Either:
■Physical Memory Limits: Windows Vista
■Physical Memory Limits: Windows XP

ANYONE: Do YOU have a machine with a 32-bit version of XP Pro or 32-bit version of Vista, with the PAE switch enabled, which recognizes more than 4 GB of RAM?

Yes, but the OS only uses 3GB...
You can install 4GB but the OS simply ignores 1GB of RAM

That's not true.

Windows 2000 and 32-bit XP allocates 2GB for user-mode processes, and 2GB to kernel-mode processes. This allocation only becomes a problem when you start using close to 2GB of RAM. If you get close to that, you can put the /3GB switch in your BOOT.INI. That will change your allocation to 3GB/1GB user/kernel.

Regardless, some space in the range from 3GB to 4GB is mapped for access to your PCI/PCI-X/PCI-Express cards.

PAE on 2000 and 32-bit XP increases your addressable memory to 36 bits, or 64GB (16GB on older implementations). This is a memory window hack (like EMS in the DOS days) implemented in Xeons and Opterons. This goes into the BOOT.INI as well.

In 32-bit land, you can go with NUMA for large memory access. NUMA works in 64-bit as well, but 64-bit doesn't really have the same adressing limitations. Even 32-bit apps running on 64-bit benefit, as EACH PROCESS has access to its own 32-bit address space - that's 4GB per program. Not too shabby, in other words.

Two of my machines have over 4GB of RAM (one has 8GB, and the other 12GB)... they're both servers. My desktops have between 512MB and 2GB each. FWIW, I can run Vista (32-bit) fine on 1GB with Visual Studio, and tons of other programs running. 64-bit Vista seems to want more like 2GB in my experience. I can't comment on gaming requirements, though.

Just for giggles, new 64-bit Windows versions support a minimum of 16TB (yes, terabytes), with a 8TB/8TG user/kernel split. Each app has a 128GB address pool.

Cheers

 

[jj14]

If Vista truely is able to sport 128gb of RAM then we need much larger mobo's.

Where did you come up with 128GB of RAM, i said 8GB before... :?
I can envision motherboards stacked up like a parking garage 16 high to hold 128GB of RAM....lol

I realize this is an old post, but just read an article at AT http://www.anandtech.com/weblog/showpost.aspx?i=481
They were describing a Nehalem server with 144GB memory

 

[zenmaster]

CypherDude,

XP SP0 would use PAE to recognize over 4GB of RAM.

XP SP1 removed the support due to issues caused by many drivers when this was done since driver vendors were simply not testing this configuration.

Vista Never had that support.

64-Bit Versions of XP and Vista support far more RAM than will ever be physically installable into a PC until a point in time that both are very archaic operating systems.

Windows Server 2003 EnterPrise Edition would be the closest thing to XP you can use to recognize over 4gb of RAM for a 32-bit Windows OS. And Yes, I have some of thse machines setup.

For a Home User, They really should be using a 64-bit OS if they need that much memory.

 

[crookdexter]

Windows XP Pro can use up to 4GB of RAM, but when you first install all of it you will only see 3 GB. this is caused by one or both of the following;
1. There is a BIOS setting that uses a portion of the RAM ans a temp file backup solution, which can be disabled in the BIOS.
2. Add the /PAE switch to the boot.ini file, this will access the full 4GB, but will limit 2GB to the OS and 2GB to other programs. If you add the /3GB switch after the /PAE it will allocate 1GB RAM to the OS, and 3GB to all other apps.

could you tell me how to add the PAE switch. It would be great if you can give me detailed description on how to edit boot.ini
I have 6 GB of ram installed but it shows only 3 GB in windows xp 32. My only other option is to upgrade to 64bit OS. my email address is crookdexter@hotmail.com

 

[AKM880]

Nice, a 3yr old thread. XP can only support up to 3.5GB (most of the time) you have to have 64 BIT OS for it to recognize all your RAM. But XP 64 bit I heard has driver problems.

 

[Guest]

Look Here

http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx

 

[Kreelor]

I am so frustrated with everyone who writes about the MAXIMUM AMOUNT of PHYSICAL RAM supported by Windows (all OS's, including 64-bit).

Nobody yet (on any of the many website's I've visited, including this one) has made an actual statement of fact as to how we users go about using more than 4GB's OF PHYSICAL RAM. Microsoft says we can. Is MS is BSing or not when they state on their own website that Windows can support up to 128GB's RAM!

Of course, each version of Windows has its own Maximum Limit, including 64bit versions.

QUESTION: HAS ANY ONE OF YOU EVER INSTALLED 16GB's OR MORE RAM ON ANY VERSION OF MICROSOFT'S OPERATING SYSTEMS --- AND, ACTUALLY HAD YOUR SYSTEM USE IT?

IF SO, will you please explain to the rest of the world exactly how you did it? Thousands of people are arguing over this issue endlessly.

I'm thoroughly confused. Is it a lie or not when MS says it's OS can "SUPPORT 128GB PHYSICAL RAM?"

 

[Guest]

32bit operating systems use 32bits for memory address space. which is about 4GB of addressable memory. This address space is for all devices requiring memory address space,

Example:
you have 4GB of ram installed, and a graphics card with 1GB of ram installed -
the graphics card requires 1GB of address space so windows can only use 3GB of your installed ram.

Other hardware devices also use memory address space, so the amount of ram that 32bit operating systems can use is dependant on what's installed in your computer. However it's pointless puting more than 4GB of memory in a machine running an XP 32bit operating system or earlier (not sure about 32bit Vista).

64bit operating systems use 37bit memory address space which equates to around 128GB of memory address space.

The /3GB switch will not allow you to recognise more memory, it just allocates 3GB of memory to applications and what's left over to the operating system. This is ok if you just run 1 application that requires a huge amount of ram, but if you have lots of background processes running (as do most computers) your operating system may run out of memory. Using the 3GB switch is not much use in most cases.

PAE mentined only works with certain Intel CPU's.

32bit Windows server operating systems can address more memory depending on the OS version.

There maybe extended memory managers available but i don't know how good they might be.

 

[Kreelor]

32bit operating systems use 32bits for memory address space. which is about 4GB of addressable memory. This address space is for all devices requiring memory address space,

Example:
you have 4GB of ram installed, and a graphics card with 1GB of ram installed -
the graphics card requires 1GB of address space so windows can only use 3GB of your installed ram.

Other hardware devices also use memory address space, so the amount of ram that 32bit operating systems can use is dependant on what's installed in your computer. However it's pointless puting more than 4GB of memory in a machine running an XP 32bit operating system or earlier (not sure about 32bit Vista).

64bit operating systems use 37bit memory address space which equates to around 128GB of memory address space.

The /3GB switch will not allow you to recognise more memory, it just allocates 3GB of memory to applications and what's left over to the operating system. This is ok if you just run 1 application that requires a huge amount of ram, but if you have lots of background processes running (as do most computers) your operating system may run out of memory. Using the 3GB switch is not much use in most cases.

PAE mentined only works with certain Intel CPU's.

32bit Windows server operating systems can address more memory depending on the OS version.

There maybe extended memory managers available but i don't know how good they might be.

I'm very sorry, but your reply (if it was to my post?) sounds like the same confusion that everybody else posts. It's vague, to say the least.

It doesn't get close to answering my questions with specific information. I'm still confused, as I feel my questions went unanswered by you (or anyone else on this forum)!

Geeesh! It was just a couple simple questions that anybody who was a "quasi-expert" with experience could have answered. My questions are NOT VAGUE!

 

[Guest]

I'm very sorry Keelor, but your question was answered and very well I must say.

I had the same questions and confusion you have and after reading that last post my confusion faded away.

32-bit processors have the limits imposed for 32-bit addressing... Where's the hard part?

The flags for boot.ini only rearrange the amounts for OS and processes... I fail to note the complication here...

Did you even read the post? Are you just looking for a "YES YOU CAN HAVE ENDLESSLY AMOUNTS OF RAM NO MATTER YOUR PROCESSOR ARCHITECTURE. JUST DO THIS:..... "

The answer is plain simple... You can't address more memory than your arch supports.

I'm very sorry, but your reply (if it was to my post?) sounds like the same confusion that everybody else posts. It's vague, to say the least.

It doesn't get close to answering my questions with specific information. I'm still confused, as I feel my questions went unanswered by you (or anyone else on this forum)!

Geeesh! It was just a couple simple questions that anybody who was a "quasi-expert" with experience could have answered. My questions are NOT VAGUE!

 

[Wolfshadw]

@Keelor -

In response to your question, no. I have not installed 16GB or more in any system running a Microsoft Operating system... but I should have.

I'm running a Windows 2008 server with Hyper-V. This allows me to run multiple virtual systems on one physical machine. There are a couple of limitations to this. The one most pertaining to your question is that each virtual server requires it's own memory allocation. With my system only running 8GB of RAM (see specs below), and me not wanting to give each system less than 2GB memory allocation, I can only run 3 virtual systems at a time. Current configurations is as follows:

Server 2008 - 2GB
Virtual Server 2003 (SQL) - 2GB
Virtual Server 2003 (IIS) - 2GB
Virtual XPSP3/Vista/7 (development)- 2GB

If I had 16 GB or more RAM installed, I wouldn't have to switch between my development virtual machines while keeping my IIS and SQL servers running. I could also run more SQL Servers (2005, 2008) and maybe even an Exchange server.

So yes. There is a use for having more than 8 GB of RAM installed on a system.

-Wolf sends

 

[Kreelor]

32bit operating systems use 32bits for memory address space. which is about 4GB of addressable memory. This address space is for all devices requiring memory address space,

Example:
you have 4GB of ram installed, and a graphics card with 1GB of ram installed -
the graphics card requires 1GB of address space so windows can only use 3GB of your installed ram.

Other hardware devices also use memory address space, so the amount of ram that 32bit operating systems can use is dependant on what's installed in your computer. However it's pointless puting more than 4GB of memory in a machine running an XP 32bit operating system or earlier (not sure about 32bit Vista).

64bit operating systems use 37bit memory address space which equates to around 128GB of memory address space.

The /3GB switch will not allow you to recognise more memory, it just allocates 3GB of memory to applications and what's left over to the operating system. This is ok if you just run 1 application that requires a huge amount of ram, but if you have lots of background processes running (as do most computers) your operating system may run out of memory. Using the 3GB switch is not much use in most cases.

PAE mentined only works with certain Intel CPU's.

32bit Windows server operating systems can address more memory depending on the OS version.

There maybe extended memory managers available but i don't know how good they might be.

Dear Anonymous,

Thank you for replying. However, your reply might have gotten closer to the actual questions that I asked (quoted below this). I do understand what you said (kinda?)?

QUESTION: HAS ANY ONE OF YOU EVER INSTALLED 16GB's OR MORE RAM ON ANY VERSION OF MICROSOFT'S OPERATING SYSTEMS --- AND, ACTUALLY HAD YOUR SYSTEM USE IT?

IF SO, will you please explain to the rest of the world exactly how you did it? Thousands of people are arguing over this issue endlessly.

I'm thoroughly confused. Is it a lie or not when MS says it's OS can "SUPPORT 128GB PHYSICAL RAM?"

First of all, your "Example".

Example:
you have 4GB of ram installed, and a graphics card with 1GB of ram installed -
the graphics card requires 1GB of address space so windows can only use 3GB of your installed ram.

I have two issues with it.

Issue 1. Had you used "16GB or ram" or, even better yet, "64GB of ram" (which is only 1/2 the total amount that Microsoft says Vista 64bit can support), your answer may have revealed just what happens to the remaining amount of RAM after MS snags the 1GB for the video card and another unspecified amount for system process, etc. Your example may be absolutely correct about 4GB's of RAM, but I'm still trying to nail down Microsoft's comment, and also gain further understanding on the subject.

Quite possibly, Microsoft's use of the word "Support" in their statements is a misnomer. To me, when I read that a particular OS "can SUPPORT up to 128GB's of RAM," my conclusion is that ALL RAM NOT USED FOR THE OPERATION OF THE SYSTEM PROCESSES, ETC. WILL BE AVAILABLE FOR USE BY INSTALLED APPLICATIONS WHICH CAN BENEFIT BY MORE AVAILABLE RAM." Yet, I keep reading posts by hundreds of people who constantly refer to "OS limitations on addressing RAM".

Issue 2. (This issue probably belongs in a separate Topic. It reveals just how "newbie" I am, when it comes to such things).

If I have a video card which has 1GB RAM on it (for its own use in graphics), then why does Microsoft "steal" 1GB of RAM FROM MY INSTALLED RAM. It seems as though the 1GB RAM on my video card is absolutely redundant! You don't need to answer this, since it's off-topic.

The comment made by "Wolfshadw," (below) is interesting, although too technical for me. At least he says that he is using 8GB's RAM -- all of it! That seems to contradict what everyone else is saying. Most people are saying that there are "limitations" imposed by MS OS's acting sort of like a "3-1/2GB to 4GB barrier."

That's exactly why I asked if anyone is currently using (ALMOST ALL) of their installed 16GB's TO 128GB's of PHYSICAL RAM MEMORY. And, if so, would they PLEASE EXPLAIN IN DETAIL HOW THEY GOT PAST THE "IMPOSED BARRIER."

If anyone has or is doing that, then why doesn't MS (or BIOS) confirm the PRESENCE AND USE of that RAM?

I'm very sorry if I am failing to understand all of you. I do appreciate your replies.

-- Larry

 

[coldsleep]

Try this on for size.

Microsoft Developer Network Article

I have installed and run Windows with 32+ GB of memory. Primarily on servers, not on home PCs. I did this by running a 64-bit version of the Windows operating system.

In general, most home computers don't need more than 4 or 6 GB of memory, unless you're doing photo/video/audio editing or CAD or something similar.

The short answer:
32-bit operating systems (many hom1e installs of Windows), due to the way they keep track of memory, can't access anything more than 4 GB of memory. This wikipedia article covers it pretty well.

64-bit operating systems have a much higher limit, but they still have a maximum amount of memory they can access.

The earlier statement about 1 GB graphics card was totally incorrect. Windows doesn't know or care about how much memory your graphics card has, and does not steal memory from the computer to account for that.

EDIT: I know I shouldn't be responding to an ancient, resurrected thread, but it seems like this thread must be in the first 20 or so google hits for this issue. I'm hoping that maybe, just maybe, there will be an answer in here that satisfies people.

 

[Kreelor]

Coldsleep -- Wonderful reply.

You stated:

In general, most home computers don't need more than 4 or 6 GB of memory, unless you're doing photo/video/audio editing or CAD or something similar.

I do all of those, plus more. Actually, I am a retired Senior Technical Illustrator (nearly 30 years experience). Performed AutoCad 3D Design, Isometric Illustration to-scale, Animation, etc. Nowdays, I'm creating and editing video movies --- and, gaming! Henceforth, the desire to have "full-use" of 16GB's or RAM.

Quick questions:

1. Will ONLY servers utilize "up to" 128GB's RAM? (You said that's what you use, but I imagine that most Windows Vista 64-bit users will be interested in only what their OS's can utilize... and, how to configure it step-by-step to do so.

2. Since you've answered part of my question very good, can you also tell me what steps are required to use 16GB's of RAM (or, more) on a Windows Vista 64-bit OS? Maybe you know?

The steps will be of great interest to thousands of people who (like me) can find and read only articles and comments about the 4GB "thresholds" and "bottlenecks" imposed by MS. I don't believe I'm the only person who is still waiting for a workable solution, or a definitive statement saying that "it cannot be done currently" (regardless of MS's claims of "... SUPPORTS up to 128GB's)!" Exactly what does MS mean by "SUPPORTS?" Is it a true misnomer (or, just more marketing hype)?

Nobody (yet) has set forth a tested, step-by-step procedure that will tell users of 64-bit OS's exactly how to install/configure UPWARDS (from 4GB's) TO 128GB's OF USEABLE, ADDRESSABLE, PHYSICAL RAM. (for use with Microsoft Vista 64 (or, Windows 7xxx) OS's.

Obviously, from here on, I'll be referring to 64-bit OS's. Other posters have explained the "32-bit" OS's very well (repeatedly).

Thank you again for replying!

-- Larry