Hi all,

I have a Vista Ultimate based HTPC (which used to run MCE 2005 prior to my doing a clean Vista install) and a Win XP Pro desktop on the network. Both machines have Gigabit ethernet, and are connected via Cat 6 cable across a D-Link DGL-4300 Gigabit router. Jumbo packets are disabled on both ends. Both have latest chipset drivers, NIC drivers, Vista patches, etc installed.

 

Prior to clean-installing Vista, I was getting transfer speeds of 35 MBytes/sec between the HTPC and the WinXP Pro desktop. After clean-installing Vista, I noticed that this dropped to a measley 11 MBytes/sec!

 

I've tried several solutions, including turning off Vista's firewall (transfer rates went 11 MB/s -> 16 MB/s). I also tried turning off autotuning (no difference) and turning off remote differential compression (minimal difference).

 

Finally, I realized something important:

If I had VMC running in the background (idling mind you, ie. not playing video, not accessing network, etc), then my transfer rates were limited to 16 MB/sec with Vista's firewall off. However, if I exited completely out of VMC, then my transfer speeds shot back up to 35 MB/sec to the WinXP Pro desktop!

 

Anyone have any ideas why VMC running in the background would cause a > 50% drop in network speeds, even though VMC isn't doing anything with the network? 

have you got Vista Sp1 installed?

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TheDigitalLifeStyle.com the home of The Media Center Show!
Microsoft MVP

Yes. I think I figured out the cause! It's due to how Vista's Multimedia class scheduler throttles down network speeds to 10 packets/sec to "improve" multimedia playback. This throttling is only apparent on gigabit networks, as 100 Mb/s LANs are already saturated at this rate. For more info:

 

http://blogs.technet.com/markrussinovich/archive/2007/08/27/1833290.aspx

 

 And a solution/workaround:

http://support.microsoft.com/kb/948066

 

I applied the registry tweak from MS above, and now I get 45 MBytes/sec throughput between my Vista and WinXP Pro machines, even if VMC is running and playing a DVR-MS file! Hope this helps other users too.

 

This is a great tip, I'm not 100% sure about this, but from reading both articles it looks like on a multicore cpu with 1gig ethernet you may be best off setting to 70 packets/sec or turning it off with FFFFFFFF.

 I'm going to try this on my system and see what gives.