XADM: Enabling 4GT RAM Tuning When You Use Windows NT Server Enterprise Edition

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Article ID: 189293 - View products that this article applies to.
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The information store (Store.exe) and the directory service (Dsamain.exe) have been compiled to make use of up to 3 gigabytes (GB) of addressable memory per process when 4GT RAM Tuning is enabled in Microsoft Windows NT Server Enterprise Edition.

4GT RAM Tuning reallocates RAM within the 4-GB address space of Windows NT Server from the operating system to memory-intensive programs. If you use 4GT RAM Tuning, a memory-intensive program can use up to 3 GB of RAM (which is a 50 percent increase over the base Windows NT Server product) so that more data is cached and performance is increased.

This feature benefits programs (such as Exchange Server) that run on powerful computers with more than 2 GB of physical RAM and that can take advantage of a larger address space.

Windows NT Server Enterprise Edition supports 4GT RAM Tuning on Intel architecture servers only.


After you install Windows NT Server Enterprise Edition, you must modify the Boot.ini file to enable 4GT RAM Tuning. To enable 4GT RAM Tuning, add the /3GB parameter to the startup line.

NOTE: This change is only effective if you are using Windows NT Server Enterprise Edition. On standard Windows NT, this flag relocates the kernel, but programs are unable to access more than 2 GB.

For example:
 [boot loader]
 [operating systems]
 multi(0)disk(0)rdisk(0)partition(2)\WINNT="Windows NT Server Version 4.00"
 multi(0)disk(0)rdisk(0)partition(2)\WINNT="Windows NT Server Version 4.00
 [VGA mode]" /basevideo /sos
NOTE: Some of the preceding lines are wrapped for readability.

For additional information about 4GT RAM Tuning in Windows NT Server Enterprise Edition, click the article number below to view the article in the Microsoft Knowledge Base:
171793 Information on Application Use of 4GTRAM Tuning


Article ID: 189293 - Last Review: February 24, 2014 - Revision: 3.3
  • Microsoft Exchange Server 5.5 Standard Edition, when used with:
    • Microsoft Windows NT 4.0
kbnosurvey kbarchive kbinfo KB189293

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