Sudden Frame Rate Drops (KB3176938)

Updated 14th September (notes at bottom)

Finding your frame rate inexplicably goes from whatever is normal to about 2 frames a second?

Well you can relax to an extent, there is nothing wrong with your settings and you are not being griefed.

But you are a Windows 10 Anniversary user, and you have the KB3176938 update and it installed around 1st September. This is the cause of your problems.

This is not simply a Second Life related problem, this issue is common to all OpenGL rendered applications, including D&D Online, Runescape, and Xplane, with emerging reports from the Minecraft community.

The problem occurs when any other application steals focus from your viewer such as a web browser or going to your desktop or minimizing the SL viewer.  The SL viewer then fails to regain foreground priority until your relog.   Sometimes it can take an hour for this problem to show itself, sometimes just a few minutes.

Linden Lab are aware of the issue, and their developers are actively pursuing a resolution for the problem.  However, at the time of writing this, the only workaround they can suggest is to consider uninstalling the hotfix patch from Microsoft.

If you cannot wait for a resolution to this, which now seems likely to be a further fix from Microsoft, and you are feeling brave, here is a guide to removing updates:  http://www.howtogeek.com/235474/how-to-roll-back-builds-and-uninstall-updates-on-windows-10/

There is also a thread to follow on the Microsoft site, specific to this issue.  Although it says it affects Firestorm, the Lab confirms it is all viewers with this update:  severe performance issues on Firestorm viewer

You can also follow the issue on the Firestorm Jira: http://jira.phoenixviewer.com/browse/FIRE-20034

There is now a LL JIRA for this issue.  https://jira.secondlife.com/browse/BUG-37795



extra note:
Please be aware that whilst the workaround of uninstalling KB3176938 does solve the framerate issue, if like me, you have always had Cortana disabled, the removal will of KB3176938 will  trigger it to become activated.

One of the 'features' of the Anniversary update was to remove the "off" switch for Cortana and once activated, it cannot be turned off again without hacking the registry.

14th September

If you removed KB3176938 alas the frame rate problem returns on the update KB3176938 released last night.  The patch is cumulative, meaning that it gives you all the updates to date.  If you are therefore missing KB3176938 because you removed it, it will be included in the patch from last night.

You can follow this direct link to the MS trouble-shooter which allows you to Show or Hide updates from your PC:   http://download.microsoft.com/download/F/2/2/F22D5FDB-59CD-4275-8C95-1BE17BF70B21/wushowhide.diagcab

You can run the troubleshooter and uninstall the patches as described here: http://www.howtogeek.com/235474/how-to-roll-back-builds-and-uninstall-updates-on-windows-10/

As previously explained, unrolling the updates will enable Cortana if you previously had it disabled, because a 'feature' of the Anniversary Update was to remove your ability to turn it off.

However by following this Registry Edit which I can confirm works as I have done it myself, will turn Cortana off in Windows 10 Anniversary.   Every caution should be taken when editing the registry.  Check and double check you have made any alterations correctly and back up your registry before meddling with it!  https://www.youtube.com/watch?v=iW1heCjMe3w