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RME User Forum → Miscellaneous → Windows 10 MMCSS missing
After installing Windows 10 on my new computer, I find to my surprise, there is no Multimedia Scheduler Service in windows any longer. There is no mmcss.dll.
I tried to download both 32bit and 64-bit dll files and add them to the service. But they will not start.
So what now?
Maybe the code has been integrated into other dll's?
Could you pls describe, for what you require this or what exactly is not working for your use case?
MMCSS, gives options for controlling your audio system. Like CPU affinity and different priority settings, that you can not access by any other means. Now, program affinity and priority is something different. I have had great success in the past fiddling around with these parameters in endless different configurations. The ultimate goal, finding that one combination that lets your system fly, not one single pop or click, no matter what you do, going as low on latency as possible, this is for live usage. You could also call this a quest for stability.
One technical aspect of this would be to keep processing threads on a fixed core, using the same cache, avoiding them flying around. It can also be used to fin-grain control what cores do what, this is very important to spread load over all the cores and never overload a singel core. This also helps audio synchronizations between cores so you do not wast to much resources on this.
My setup is one daw per core and I use totalmix for syncing and mixing. This takes away lots of stress from the cpu. Because you basically off-load the digital synchronization of audio streams to the rme hardware, (almost like analog).
So without the MMCSS system, I have no way to control where the audio system is doing the processing... This can lead to some pops and click under unfortunate situations... Even if latency monitor is green for hours.
And as a kick to RME, this is why Linux would be a much more flexible and powerful option then running 50 year old windows system on modern hardware to get good results. But this is like talking to the hand. Per this day, no real audio operating system exists. One did and that was Be OS, but that got butchered.
MMSCC is present and working on Windows 10.
That being said, if you are using one DAW per core then you can just set affinity via Task-Manager (manually) or Process Lasso (automatically).
On modern hardware MMCSS has far less of an impact, because the main competition for non MMCSS ASIO threads is the Desktop Windows Manager (DWM) that runs at the same (non realtime) priority 15 as non MMCSS audio threads. That was an issue on old hardware of Vista days, but not so much anymore. For example, on my Ryzen 1800X system DWM uses less than 0.12% CPU load. MMCSS is still a nice compromise to "real" realtime priorities, especially on a busy system (background processes).
I do use Process Lasso Timur it is a great utility. How do I verify that indeed MMCSS is present. As I said, the service is hidden, does not show up there, in the list. The mmcss.dll file is gone... ???
Thanks for inside info :-)
Check the audio thread priorities via Process Explorer (Sysinternals). Usually they are 24-26, Reaper also uses 22 on at least one thread. Then run Prime95 at 100% load, which uses Priority 1. The MMCSS threads will drop to priority 0 (unless that part was changed in W10) for 10-20% of the time in order to make room for the Prime95 threads.
Keep in mind that some DAWs handle this themselves, some DAWs don't handle it at all and Ableton Live actively suppresses MMCSS (last time I checked). You can also activate/deactivate it in the RME driver, which depending on the DAW you should do or should not do.
This is what I posted last week in the Sonar forum:
Turn off RME MMCSS for Sonar, Sonar will activate it on its own.
Turn off RME MMCSS for Live, Live would deactivate it anyway (unless it's bugged again).
Turn on RME MMCSS for Cubase, Steinberg expect this to be handled by the driver instead of the DAW (and wants all DAWs and drivers to work that way).
I use a different daw, minihost, just to be clear. I never used Process Explorer before, so I downloaded to give it a try. But I can not find anything resembling what you suggested...
So I have no indication that MMCSS is running or doing it's thing. I do not get any error, when trying to use MMCSS in host or with driver.
Double-click on a process in Process Explorer then change to the "Threads" tab. It will show all running threads of that process. You will see a list of entries like:
"5616 0.06 38.094.173 fireface_usb_asio_64.dll+0x1af0"
If you select an entry you will see the thread's base priority and dynamic priority. MMCSS threads usually run between 24 to 26. If you run Prime95 Small FFT on all cores you will see the MMCSS priority dip to 1 occasionally (may have to increase Process Explorer refresh-rate), that is the 10-20% reserve for background processes (Prime95 running 100% at priority 1 itself).
PS: I had to answer three (3) anti-spambot questions to post this. 
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RME User Forum → Miscellaneous → Windows 10 MMCSS missing
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