Solving the error: "ANOMALY: use of REX.w is meaningless"

Fri, 21/10/2016 - 12:39 -- James Oakley
Trend Micro

I'll post this here in case anyone else is searching for this issue

Since my computer updated to Windows 10, build number 1607 (also known as the "Anniversary Update", because it was a feature release timed to coincide with a year since the first release of Windows 10), I've been getting an error when I try to run any command in a command prompt window:

[0x7FFCF5BB70E3] ANOMALY: use of REX.w is meaningless (default operand size is 64)

The first part, in square brackets, is a hexadecimal number (as seen by the "0x" with which it begins). I do not know what that refers to. It is always the same on my computer. I believe it is unique to me - I've seen other people report this error online, and they gave a different hex number. I also searched on Google for 0x7FFCF5BB70E3 and found nothing.

It seems this is a conflict between Trend Micro's anti-virus protection and Windows 10 build 1607. Reading other webpages that discuss this, it seems Trend Micro have solved this, but have not yet issued a program update (through the built-in updates mechanism) to address. Why they've not released their fix is beyond me.

However, apparently, if you ask their support department, they'll give you the hotfix you need.

Sure enough, one short, very helpful and efficient chat session later, I have a link to their website which tells you where to download the hotfix and how to apply it. It's not hard. Visit for more information. (That link no longer works - see comment below for more details.

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Submitted by James Oakley on

It turns out that Trend Micro have removed the support page I linked in this post — probably because they've fixed this issue in a version of their product that they assume everyone is now using.

Judging by how popular this blog post is, it seems end-users are still having problems.

So: Here's what used to be on that support page (see below if you're having trouble accessing the download file):

You receive the following error message on your Command Prompt:

"[0x7FFEB62770E3] ANOMALY: use of REX.w is meaningless (the default size of the operand 64)"

This happens on a 64-bit version of the Microsoft™ Windows™ RS1 platform when Trend Micro Security 10 (2016) is running.


  • We recommend that you print out this document or bookmark this page before proceeding because you will be asked to restart your computer during the procedure.
  • This hotfix is only applicable to Trend Micro Security 10 (2016).

To resolve the issue, do the following:

  1. Log on to your computer using an account with administrator privileges.Note: If you have installed a software on your computer before, you have these privileges.
  2. Click the button below to download the hotfix.Download HotfixDouble-click the Ti_100_win_en_AMSP38_UMH_hfb1267.exe icon to run it.
  3. Click Yes when the User Account Control appears.
  4. Choose I accept the license agreement, then click Next.
  5. Click Install.
  6. Click OK when a warning window appears.Note: An installation successful message will appear after you finished installing the hotfix.
  7. Restart your computer.

Note on the download file:

At the time of writing this comment (10 April 2017), the download link linked within the knowledgebase article still worked. However, as the knowledgebase article has gone from their website, it's possible that the download file will as well.

So, here are two you can try: (i) the patch linked above: Ti_100_win_en_AMSP38_UMH_hfb1267.exe; (ii) the different version of that patch that was linked from their knowledgebase when I had to apply the patch to my own computer: Ti_110_win_en_amsp50_UMH_hfb2.5.2017.exe.

Please use the link that downloads directly from their website, for as long as that still works, as you then know that you're accessing their original file. Always download files from the original author's site, rather than a mirrored copy, if you can. Please note: I can accept no responsibility for the consequences of you following the instructions on this page and/or using either of the download files I've mirrored for your convenience.

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