Windows 7 lag when using dual monitors with different refresh rates

I have recently installed Windows 7 Ultimate x64 with Service Pack 1, coming from Vista (in which I had no problems). After the installation, the first thing I did was install the graphics card driver for my AMD Radeon HD 6870 1GB card. I then noticed that when I drag windows around the desktop, scroll through windows, and especially drag windows from the secondary monitor to the primary, there was very noticeable lag. However, there was no lag in games – just the Windows desktop and its windows. This was a completely fresh install. I have dual monitors – the primary is a 19″ widescreen Acer X191W, and the secondary is a 15″ Sony LCD. I am using them in extended desktop mode.

What happened at first was Windows locked the primary monitor to 75Hz, and would not let me change it to 60Hz.  For some reason the first time I installed the video drivers, I think there was a conflict with the default Windows display drivers, causing my main monitor to be stuck at 75Hz. I had to uninstall and wipe the display driver to reinstall it, after which the option to set it to 60Hz appeared. I used ATIMAN Uninstaller to wipe the driver. After setting the display to 60Hz, the lag disappeared completely.

So it seemed there was a conflict somewhere with my specific hardware configuration that caused lag when two monitors were set to different refresh rates. However, then I tried to recreate the problem on a different system. This system has a Radeon HD 4870 and different dual displays. It had the same problem when one of the monitors was set to refresh at 60Hz and the other at 75Hz. And again, putting them both to 60Hz resolved the lag issue.

I could not find any information about this issue online. It can’t be the monitors as between the two systems there were four different monitors that had the same problem. It can’t be the hardware, because my computer has a 6870 and the other has a 4870. It can’t be interfering software, as this was a clean install of Windows. It has to be either the AMD driver, or an issue with Windows.

The point of this post is to let people know how to fix this issue, as well as ask if anyone else has experienced this, especially with a different graphics card. It took me two weeks to find the cause of this. I haven’t found anyone online with this issue. Both the video cards I tested should handle different refresh rates without a problem. Although I have fixed the issue, I still want to know what caused it.

3 thoughts on “Windows 7 lag when using dual monitors with different refresh rates

  1. Just to let you know I have similar observations. With me it would go away temporarily if I used flip 3D allot and moved windows back and forth. (Almost loosening it up) But then it would return next window I moved to second monitor. I’ve uninstalled my Nvidia driver and (for nvidia 8800gts ) which displayed 60Hz but kept jumping back to 75hz. With the defualt windows installed driver i’ve set both to 60Hz and i’ve yet to see the lag return. Thanks for your post I probably never would have figured this out myself.

  2. Thanks for posting this. I had the same issue with a user who was running 3 monitors that were all the same at first until I tried going the quick route and swapping out the monitors. Whent that didn’t work I found this post and read through and tried setting the rerfresh rates to be all the same. I soon found that they were all set at 60hz already. I saw that the user had the latest NVIDIA driver (04/11) so I rolled it back to a previous driver and viola! Hope this helps.

  3. Hi!

    I had the same issue with my Samsung monitor and Samsung TV as secondary. I had no issues on Vista 64bit, so I couldn’t figure out whats wrong. As I only watch movies on the TV I first thought its a video codec problem, as all the movies were laggy…I tried, codec packs, reinstalled directx , all kinds of system related drivers, all kinds of players but everything was really slow on the TV and no problems on the primary display. I have just set the TV to 60Hz from 24 and now its all smooth any nice! Many thanks, I would never figure this out by my own!

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