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What is XP's maximum addressable memory?

by MuleHeadJoe / July 13, 2005 6:48 AM PDT

Looking at new computers with Win XP Pro, they all seem to top out at 2 Gigs of RAM ... even those with 4 DIMM slots. Since 1GB ram sticks are relatively affordable nowadays, I'd like to maximize the capabilities of my next system as much as possible.

Is the amount of addressable memory a limitation of the hardware or the OS ?

tia, MHJ.

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by slim___shady / July 13, 2005 7:03 AM PDT

it depends on how many address lines the CPU has. A 32-bit CPU can have 2^32 = 4294967296 addresses. I think.

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Hardware limits, not O/S
by Dick White / July 13, 2005 7:08 AM PDT

Though I haven't searched the Microsoft documentation for theoretic limits, I haven't ever heard anyone say the operating system imposes any practical limits. Usually the practical limit is hardware - number of memory slots times memory stick capacity. The number of slots is easy enough to count just by looking, but the addressable capacity per slot may have some inherent limitations in the bit length of the memory addressing scheme, which you won't find readily in the end-user documentation. That means you have to assume it is implicit in the manufacturer's guidance of maximum memory. I've seen a number of 3-slot boards state a 3G max, but perhaps the ones you are looking at have a real 2G max (and were built with 4 slots based on the memory market being mostly 512M modules), or perhaps it is just old marketing information from back when the earth was still flat and 1G modules hadn't been invented. You might check the mobo manufacturer's website to see if they have changed the technical specs despite what you see on the retail sales page.


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Memory Limits
by islandporgy / July 15, 2005 6:19 AM PDT

This topic could not have come up at a better time.
I have on my system Atholon XP 3200 with Gigabyte GA 7NNXP motherboard, And 2 gigs off double sided memory & 1 gig off single sided memory at PC 3200, And a XFX 256 Ultra Video card. When I only had 2gigs off double sided memory not running at Dual channel my computer was runnig find. When I added 1 gig of single sided memory now running Dual Channel, My computer now shuts off with out any warning. I called up Gigabyte to ask them if there was any settings inside Bios that needs to be set and they blamed it on the memory. The specs on the motherboard say max is 3 gigs. I tried all diffrent kinds off combonation with the slots but still same results. I do believe there might be limatations on hardware.

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by Dick White / July 15, 2005 6:40 AM PDT
In reply to: Memory Limits

if your computer justs shuts off without warning, it could be any of several hardware failures - power supply, video card, etc. But let's say it is absolutely memory related because, let's just say for the purposes of argument (and please do test this for real on your own later...) you took the new stick out and the computer hasn't shut down randomly ever since, but then you put it back in and now it does again, which proves that the memory is causing it...

You could have a faulty stick of memory. It happens. You could possibly beg or borrow a similar stick and try it. If it too fails, then the stick itself is probably ok.

You could have some issues with the dual channel attempt. Typically dual channel likes balanced channels. Three is an odd number, unbalanced. What happens when you turn off the dual channel setting and let it have a 3G single channel?

Have you tried swapping the sticks around in the slots? I don't think the double vs. single sidedness of the chips should matter, but what happens if you use one old and one new stick (for 2G total) which used to work with both sticks old?


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Memory Dual Channel
by islandporgy / July 15, 2005 2:12 PM PDT
In reply to: memory...

With this Gigabyte motherboard GA7NNXP to activate dual channel You have to have what the manuel say 1 double sided & 1 single sided module, and have them in the proper slots. Not in the correct slots know dual channel and it does not register as not having any memory at all.
I could have a bad moduel and that could be my single channel moduel. I will try it with one single and one double for a while to see what happens all the rest of my hardware is in good shape. And about Balance channels I heard off a lot of complaints about some Gigabyte motherboards with Dual channel.
Channel A: is Dim 1 & 2
Channel B: is Dim 3 & 4
They have a lot of differen Sequences on set up the moduels to get dual channel. You can get it with 2 moduels and get it with 3 moduels. I am going to try one of each. And then I am going to try it in my other computer which also has a gigabyte mobo and dual channel technology.
Thank You

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Not completely sure of this but,
by mustangj36 / July 15, 2005 12:30 PM PDT
In reply to: Memory Limits

I believe that if you run memory in dual channel mode, it must be installed in matched pairs, otherwise it won't work.

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Matched Pairs
by islandporgy / July 15, 2005 2:36 PM PDT

I have on my mother board GA7NNXP 1 single & 2 double When you reboot it tells you each time that you are in dual channel mode Gigabyte Mobos are different. I had 2 double sided in the begining and I was running in dual channel mode then I got one single sided just to max out my memory and I am still in duel channel mode. On this Mobo you do not have to have it in pairs. The Motherboard has 4 dims I am using 3. My mobo specs says it can handle 3 gigs of memory Two sticks to four sticks

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Dual Channel
by baer57 / July 22, 2005 11:50 PM PDT
In reply to: Matched Pairs

It might tell you it is in Dual Mode but there is a problem otherwise it wouldn't shut down. I suspect you ahve to have matched pairs, as with everyone I have heard about and seen you did, as far as 3 gig limit you were supposed to use matched set of 512 meg to get the other gig. try first taking out the 1 gig module and see if it doesn't clear it up.

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by tinyworld09 / January 17, 2009 8:36 AM PST
In reply to: Memory Limits

I used to have Gigabyte ram it gave me BSOD every time so I bought corsair ram and it works for 2 years without BSOD.

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4GB variable...
by John.Wilkinson / July 13, 2005 8:31 AM PDT

Windows XP 32-bit edition can only address up to 4GB of RAM. However, hardware limitations often prevent this much from being used. In addition, the average consumer doesn't need, and won't receive much, if any, of a boost from this much RAM. For most, 512MB is fine, 1GB ideal, and 2GB a little excessive.

Windows XP Professional 64-bit edition, on the other hand, supports up to 128GB of physical RAM and 16TB (terabytes) of virtual memory. Currently, I'm unaware of any consumer-focused motherboards that can handle more than 4GB, but they should become available in the near future, most likely after Longhorn is released.

Hope this helps,

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What is XP's maximum addressable memory?
by gary hall / July 14, 2005 11:49 PM PDT

I run a P4 3.4 MHz, Intel mother board, 2 gigs 512 DDR2 RAM, 800 FSB and 2 Western Digital 10,000 RPM drives in a RAID 1 configuration.

I have regularly looked at Windows Task Manager and have never seen any of the ?normal? programs EVER come close to 1 gig usage. In order to exceed 1 gig I have to load up just about everything I have on the machine.

IMHO, the Microsoft Programs have been designed NOT to use more than 50,000 K. As I type this in Word 2003 I am using 37,524 K. Mozilla uses the most at 77,424 K. The total for everything I am running is 394 MB. Only rarely do I exceed 1 gig.

Currently I am running several real-time processes (setiathome_4.18_windows . . . . ) and the most they use (both CPU?s) 50,000 K and even those that I allow to use 98% CPU usage does not make a difference.

Save your money and don?t go over a gig.

Warm regards,


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What is XP's maximum addressable memory?
by lawillia / July 15, 2005 2:03 AM PDT

This is a Harware and Software limit for 32 bit processors and 32 OS/applications. You can use more than 1 gig but you have to tell the OS to do so. There is a registry setting to let you tweak this. I would recommend using another type of OS if you are going to use more than 2 gig of RAM. Windows even 64 bit XP or 2003 has issues when addressing or being about to use more than 2 gigs of ram properly. More ram is better but it depends on what you are doing. You might look at Linux or Mac OS if you would like to utilize > 2 Gig of ram.

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using more RAM
by MuleHeadJoe / July 15, 2005 4:56 AM PDT

I have to admit I don't have any 'graven-in-stone' requirements for over 1 GB of RAM, I just like the idea of having as much memory as possible available.

The most memory intensive stuff I do is gaming and web browsing. I do generally qualify as a "power user" based on my habits ... I usually keep several applications loaded up even if I'm not using them all. And with regards to web browsing ... I like to have multiple windows open, and have had up to 30 ro 40 browsers in play at one time (currently on an AMD 2700+ with 1GB ram). When I had only 512 MB of ram, on an older AMD cpu, I could not get more than 30 IE windows to display before I started losing content and encountering strange behavior leading to the app crashing. Based on what the symptoms were, it looked to me to be a memory issue, but I don't know if these windows are stored in central storage or in the dedicated video ram. My old machine had 32meg video ram, and the current one has 64. I imagine my next machine will have a 128 meg card.

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by ackmondual / July 15, 2005 9:24 AM PDT
In reply to: using more RAM

For my Dell Dimension 8300, it's got 4 DIMM slots and maxes out at 4GB. Using winXP Pro as well.

Well, if you're spending more $$ on stuff that u don't need (like RAM), then it is a waste of $$. Of course for some ppl myself included, being that it's nice to know it's there does give that warm fuzzy feeling.

256 - good for winXP and small simultaneous # of basic tasks like small Word files, email, internet.

512 - even better for basic, but more files and larger of them. Also better for PC gaming

1024 - Most ideal for PC gaming. Can have many many tasks open simult.

1.5 to 2GB - good and great for ppl who do heavy video editting or do multiple high resource apps at the same time (e.g. you're playing Doom3, downloading stuff on a p2p program, burning a DVD, while compressing a video file using VirtualDub)

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using more RAM
by gary hall / July 23, 2005 2:23 AM PDT
In reply to: using more RAM

I just opened up Photoshop and loaded 40 - ~1.3 MB pictures. Windows Task Manager showed that the "Commit Charge was 1284 M/3942 M. (I have 2 GB DDR2 512 PAIRED memory.)

Photoshop indicated 820,620 K. I could have opened a lot more pictures without any degrade in performance IMHO.

Soooooo, if you are NOT using things like PS and movie editing, then I doubt seriously if you will ever need more than 1 GB RAM.

Also, it is very possible that newer memory will be designed for the Visa OS (Longhorn). It would be faster and more expensive (What's new) but would optimize data transfer better. The newer MOBO's will have faster FSB's too.

In other words, what you are using today most likely will not work (effectively) with the newer MOBO's that will take advantage of the 64 bit OS's.

My $.02.

Warm regards,


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by MarkinTO / July 15, 2005 1:50 PM PDT

You almost answered your own question. If your familiyar with higher level maths, you'd realize that a 32-bit processor can only access so much memory, even on a good day!

Whilst you've most likely been told get as much RAM as you can, which is in itself good advice, there does come a limit to this.

I run a video production company and find that all my machines are happy as long as they have 1 Giga-byte of memory.

The things to remember are, use the fastest memory your motherboard supports. You'll likely never need more than 1 Giga-byte. Keep in mind that software will enhance your available memory by using hard-drive space to swap files as well.

To increase speeds more, consider 10,000rpm IDE hard-drives or hard drives with caches of 8Megs or, if your motherboard supports it; newer serial IDE drives, AGP 16x or PCI express video cards or if you have lots of bucks RAID drives?

I still use 7,200 rpm drives, agp graphics and fire-wire for video & have no problems.

Best of luck, with your speed...


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by gary hall / July 16, 2005 5:31 AM PDT
In reply to: Memory...

The new replacement drives for IDE are called SATA drives which I use. The big cache and very fast access times beat the IDE drives some 3 to 4 times and that is an improvement of major prorportions without spending the big bucks. You do need a mother board that will accept them however.

Also the FSB speed is important. What good is fast paired memory and fast drives if you can't move the data. Intel has one mother board with 1024 FSB (correct me if I got the speed wrong) and the board I got has an FSB (Front Side Bus) of 800 (I could not get the faster one).

Most home come computers (1.0 / 2.0 MHz) are 400 FSB. So think about that befor going headlong in getting new drives etc.

There is a serious discussion going on right now IF there is any benifit using DDR II 512 paired ram over regular ram - sorry it is waaaaay over my head. Just passing the info on. My 2 gig (DDR II 512) cost me $600.00 last December - something else to think about.

Warm regards,


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by tek01 / July 18, 2005 4:45 PM PDT

If you are running a memory intensive application like AutoCad, Inventor or Mechanical Desktop, from Autodesk then the more memory the better. In fact they recommend a min of 1G for very simple stuff and 4G for more complex modeling. For acesss to memory above 3G it is necessary to include the /3G switch on OS bootup. Better knowledge than mine plus a more comprehensive discription can be found on the Autodesk web site and of course Microsoft. I also suspect that Kingston site (memory manufacturer) may also have info that could help !

good luck !

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Max Memory ...
by vince7 / July 28, 2005 7:35 AM PDT

I am from the school that you can never have enough RAM. I run XP Pro SP2 on a P4 2.6 Gig 800 FSB desktop. Installed is 4 gig of Dual Channel PC3200 RAM. Hyperthreading is enabled also. I have at startup about six icons in the Systray. These include firewall, antivirus, popup blocker, MS Anti-spyware Beta, EWIDO, Quick fix and Clock-X.

Then I Open Outlook, IE, Pal Talk, MSN Msg and Yahoo. I might play music from my playlist or from a CD. To help the computer perform better I turned off the page file. I have two 10,000 RPM Raptors is RAID 0, with a 7200 rpm 80 gig HD for my archieve. All unnecessary services are disabled. I also have a 120 gig Fantom Firewire external drive for my music files. I won't mention the 3 printers, scanner and 3 camera attached too. Get all the RAM you can afford!

One last thing ... this is a Dell 4600 Happy

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And how much of that do you use?
by John.Wilkinson / July 28, 2005 11:11 AM PDT
In reply to: Max Memory ...

Do ctrl+alt+del and on the Performance tab, see how much Physical Memory you are actually using, then see how many programs you have to run at once to even come close to the full 4GB. For the average user, 4GB is completely unneeded. While you may need/use that much RAM, I'm gonna go out on a limb and say that you'll max out your processor long before you need to tap your paging file. (I foresee a dual-core processor in your future, as your current 2.6GHz P4 w/HT is just slowing you down!) Wink


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Max Memory supported as per Micro$oft.
by cny3axg / July 23, 2007 8:54 PM PDT

Memory Support and Windows Operating Systems
Updated: February 9, 2005

Operating systems based on Microsoft Windows NT technologies have always provided applications with a flat 32-bit virtual address space that describes 4 gigabytes (GB) of virtual memory. The address space is usually split so that 2 GB of address space is directly accessible to the application and the other 2 GB is only accessible to the Windows executive software.

The 32-bit versions of the Windows 2000 Advanced Server and Windows NT Server 4.0, Enterprise Edition, operating systems were the first versions of Windows to provide applications with a 3-GB flat virtual address space, with the kernel and executive components using only 1 GB. In response to customer requests, Microsoft has expanded the availability of this support to the 32-bit version of Windows XP Professional and all 32-bit versions of Windows Server 2003.

Windows 2000 Memory Support. With Windows 2000 Professional and Server, the maximum amount of memory that can be supported is 4 GB (identical to Windows NT 4.0, as described later in this section). However, Windows 2000 Advanced Server supports 8 GB of physical RAM and Windows 2000 Datacenter Server supports 32 GB of physical RAM using the PAE feature of the IA-32 processor family, beginning with Intel Pentium Pro and later.

Windows XP Professional and Windows Server 2003 Memory Support. The maximum amount of memory that can be supported on Windows XP Professional and Windows Server 2003 is also 4 GB. However, Windows Server 2003, Enterprise Edition supports 32 GB of physical RAM and Windows Server 2003, Datacenter Edition supports 64 GB of physical RAM using the PAE feature.

For more information, utilize the link above.

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Follow this link
by FrankQC / January 19, 2009 10:38 PM PST
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Im about as confused as a baby in a ***** bar...
by mosfet303 / May 28, 2009 8:30 AM PDT
In reply to: Follow this link

This thread is pretty old just in case there is anyone still watching, I am running XP Pro SP3 and had 2 one gig dual channel sticks running fine. windows said it was two gigs, so now I just added two more 1 gigs now totaling 4 gigs of RAM. Bios says there 4 gigs avail 4 gigs usable and windows under system info says 3 gigs.

Ive spent the last 2 hours sifting through msg board after msg board every ones saying XP home sees up to 3 gigs and pro sees 4+ then others say any windows 32 bit will not see over 3 gigs. But I see MORE 4 gig responses for XP home or pro. According to the previous posts link XP home sees 4 Gigs. Now.... which is it, did i waste my money on the extra gig of ram or is one of my sticks bad? Is this just another a reason to buy an MAC?

Hmmmm Vista64 or switch to MAC

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Memory Maximum for Windows Xp Professional OS
by stedge / June 22, 2009 4:39 AM PDT

The maximum amount of memory for a Windows XP Professional installion is 4GB.


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XP Addessable memory- W4300 HP Workstation
by cz70 / October 26, 2009 9:06 AM PDT

This machine has and recognizes 4096 MD of memory... 4 1GB sticks. It runs XP Pro. One of the fastest machines I've ever worked with. Only improvement would be if it utilized hyper-threading.


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