Dell Optiplex 745 with 4GB of RAM; Win XP Pro only sees 3GB.

Posted on 2007-10-18
Last Modified: 2012-06-27
I have a Dell Optiplex 745 with 4GB of RAM; Win XP Pro only sees 3GB.

Will adding the /3GB switch in the boot.ini file resolve this issue?  IF not what else would I change?

Is there a downside in trying to get this last 1GB of RAM?
Question by:itplatoon
    LVL 8

    Assisted Solution

    You need Windows XP 64Bit in order to fully use all 4GB, and the /3GB will not resolve anything.
    LVL 70

    Accepted Solution

    There is not much you can do - its down to the way a 32bit OS addresses the RAM. In theory a 32bit OS can address 4Gb but in reality some on that address space is used to control i/o operations etc so isn't available to to be used for memory addressing. The result is that it you put 4Gb in a OC the top bit of memory cannot be used. This typically results in between 3.25 and 3.75Gb  being usable.


    to make full use of 4Gb you reallt need a 64bit OS.
    LVL 59

    Assisted Solution

    If you do a search of Experts-Exchange Previously Answered Questions, you will find questions like yours asked MANY MANY times.  I will add my two cents to what Mikkk says above:

    From this question:

    It's worth noting that WinXP, while the 32-bit version does indeed "support" 4GB, Windows splits the 4 GB of available memory address space into two separate 2 GB address spaces. One of the 2 GB address spaces is used by the Windows operating system, and the other 2 GB address space is used for user mode processes (applications).

    However, there is a /3GB switch used in the BOOT.INI file. The /3GB switch changes the memory allocation so that Windows is only allocated 1 GB of address space, and user mode processes are allocated 3 GB of address space. Splitting the address space like this helps Windows to better manage high demand applications. However, Windows is configured to have a 2 GB address space for the operating system for a reason. If you use the /3GB switch, you can severely impact Windows ability to run multiple applications simultaneously.

    Also, there is this MSKB article:;en-us;888137
    The amount of RAM reported by the System Properties dialog box and the System Information tool is less than you expect after you install Windows XP Service Pack 2

    Featured Post

    Highfive Gives IT Their Time Back

    Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

    Join & Write a Comment

    Suggested Solutions

    What do we know about Legacy Video Conferencing? - Full IT support needed! - Complicated systems at outrageous prices! - Intense training required! Highfive believes we need to embrace a new alternative.
    In the modern office, employees tend to move around the workplace a lot more freely. Conferences, collaborative groups, flexible seating and working from home require a new level of mobility. Technology has not only changed the behavior and the expe…
    This video is in connection to the article "The case of a missing mobile phone (". It will help one to understand clearly the steps to track a lost android phone.
    Internet Business Fax to Email Made Easy - With eFax Corporate (, you'll receive a dedicated online fax number, which is used the same way as a typical analog fax number. You'll receive secure faxes in your email, fr…

    746 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    17 Experts available now in Live!

    Get 1:1 Help Now