Having to support Windows in my day to day job (I’m the Windows administrator) is a necessary evil. I was wondering why my test deployment of Windows 7 was so slow copying files. Turns out it was due to bandwidth throttling, a “feature” since Vista. Windows 7 seems to throttle bandwidth, especially on a LAN and it’s based on helping to prevent little or no interruption to audio playback. This can be damn annoying, especially when copy large files across an intranet.

Two registry settings that seem to prevent or alleviate the throttling are:

(DWORD value) HKLMsystemCurrentControlSetServiceslanmanworkstationparametersDisableBandwidthThrottling (create if it doesn’t exist and set to 1 to disable and then reboot)

or

HKLMSOFTWAREMicrosoftWindows NTCurrentVersionMultimediaSystemProfileNetworkThrottlingIndex (set to a value between 1 and 100 and reboot)

Also another possibility is to disable the MMCSS (Multimedia Class Scheduler) service – from wikipedia: “This service has been implicated in poor networking performance while multimedia is playing”, or “Windows throttles the network interfaces while audio is playing in order to maintain audio quality and prevent network interrupts interrupting media playback. By default, this limits the network receive speed to 10% of its maximum – 100Mbps on gigabit ethernet, and 10Mbps on fast ethernet”

The service is is a dependancy in the windows audio service (the dependancy needs to be removed so windows audio can still run) so in regedit,
go to HKLMSYSTEMCurrentControlSetServicesAudiosrv, find DependOnService and remove MMCSS and restart.
Finally, in the services control panel, services.msc, disable “Multimedia Class Scheduler service” and restart.

Voila!

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