/Maxmem support in Windows Vista

High-performance hardware from time to time needs direct access to memory in order work properly. That is the case with the excellent Matrox Imaging line of framegrabbers. In particular, I am using the Meteor/2 family of framegrabbers (a framegrabber is used for capturing images from a camera, usually for industrial, medical, or surveillance purposes). The driver and library that comes with these framegrabbers, Matrox Imaging Library, ensures during installation that the framegrabber has direct access to memory by adding a switch to the Windows XP’s (or NT or previous versions of windows) boot.ini file: /MAXMEM=xxxx where xxxx is the upper limit of memory (in MB) that windows will use. For example

multi(0)disk(0)rdisk(0)partition(1)\windows=”Microsoft Windows” /MAXMEM=2040

This lines reserves 8 MB (of my computers 2048 MB memory) for direct use by the framegrabber.

However, with Windows Vista this possibility changed. It does not use the boot.ini file any more. Instead, one has to use the Boot Configuration Data Editor or bcdedit. This utility can be run from the command promt (but remember to run the command prompt “As administrator” – by rightclicking and selecting “Run as administrator”).

BCDedit is explained here, at Microsoft Technet. /Maxmem is replaced by the option TRUNCATEMEMORY, and in order to get the same effect as the example above try from the command-line prompt:

bcdedit /set TRUNCATEMEMORY 2139095040

As can be seen, the limit 2040MB now needs to be specified in bytes.

After a reset, going into Control Panel – System, you can see that it has worked. In order to remove the limit, try

bcdedit /deletevalue TRUNCATEMEMORY

There should probably be a warning here: “Don’t try this at home”. Or at least don’t try it if you don’t know what you are doing. Of course, by the level this is documented by Microsoft, no one knows even half of what they are doing, so …

To the end of the story, I have not managed (yet) to get Matrox Imaging Library 7.5 to run properly on Windows Vista. On the other hand, as this blog explains, I managed to reserve memory for direct use by the hardware.

7 thoughts on “/Maxmem support in Windows Vista

  1. Marcello Poli says:

    I’m having big difficulties to install MIL Lite 7.5 under VISTA.
    Matrox foresees to release a MIL 9 for VISTA later this year.
    I’ll have lost all my clients because is every day more difficult to find a PC without VISTA installed on.
    One my friend living far from my city, told me he ha installed without problems MIL-Lite 7.5 under VISTA.
    Have you execute this installation?
    Please answer me

  2. Jon says:

    I think it installs on Vista. Well, at least I did it. The problem is that, depending on your framegrabber card, the driver might not work. In my case the IEE1394 driver did not work. Whether or not it will work with other framegrabbers, I don’t know.

  3. Marcello Poli says:

    Thanks for your reply.
    Frame grabber I use is Meteor II or Cronos Plus (separately), when the MIL setup run an error occours because under Vista the drvinst.exe program can’t install the driver.

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