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RME User Forum → Tips & Tricks → Latency monitoring utility
Anyone tried "LatencyMon", a free utility recently released by Resplendence?
http://www.resplendence.com/latencymon
Claiming to help identify the root cause of audio dropouts, clicks and pops, this may be a useful complement to the forum favourite, DPC Latency Checker. Alas I couldn't test it yet as only Windows Vista and higher is supported, not XP.
I will have a look at it once I find time. 
It would be nice to get a more comprehensive tool that is easy to use. But nothing can be as complete as Microsoft's own XPerf which mainly comes with the trouble of getting it installed. It has the edge of using the very tools that the OS offers for exactly this kind of measurements.
Main drawback of Xperf is that is writes a log which you analyze afterwards. DPC Latency Checker is a realtime tool (that does not give exact measurements though). So let's see what this LatencyMon can do.
PS: For the past few weeks I waited for NVidia to finally publish the v260.x drivers that promised to fix DPC issues. I advice everyone with issues to try it (cannot be installed yet on my bootcamped MBP though).
I just read:
Technology
LatencyMon makes use of kernel event tracing for Windows (ETW), therefore it will only run on Windows Vista and later (including Windows 7 but not Windows XP). The program loads a driver at startup which is needed to obtain virtual addresses of loaded kernel modules so that the software can resolve routine addresses to driver names. The same information that LatencyMon gathers could be obtained by running the XPERF utility which is part of the Windows Performance Analysis Tools.
Tom, thanks for that one. I tested LatencyMon with my crappy Dell Studio 1537. So far it seems this software is a big step forward compared to DPCLat, simply because it includes the information we have all been waiting for - what the *?&%$ is causing the spike.
I had no time to check the cumbersome XPerf, but Timur might be able to tell us if XPerf would bring even better results, because the information shown in LatencyMon is still not the final solution in some cases. Let me explain:
My Dell has lots of different spikes between 1 and 4 ms. So LatencyMon tells me the lower spikes are caused by ndis.sys. That means it is the network. Disable it - spikes gone. Note that ndis.sys is most probably not the culprit, it is the network driver from the network adpater that needs to be improved (Broadcom here).
The higher spikes (up to 5 ms) are identified as ACPI.sys. Well, it could have said 'Dell Studio' instead, this information is simply useless and does not point anwhere to solve the problem (Timur - same in XPerf?).
So like said before, this tool might help a lot more than DPCLat in many cases, giving more information on where to look for the problem (and I give it the thumbs up), but it will still fail in some situations.
Just a side note for Dell users: I am 100% sure that these ACPI calls are caused by the motherboard/BIOS. Dell's earlier fix on this had been incomplete. Absolutely ridiculous, I have to download updated drivers for my notebook from other companies like Toshiba and HP, as Dell stopped with outdated Vista drivers on this one a year ago, that is about half a year after its first shipment. Never again, Michael.
Using XPerf is as easy as using the two line:
"Xperf -on latency" and after some seconds/minutes of logging "Xperf -d <name>.etl"
Then you double click the ETL file and get your information. For DPC informations you go to "DPC CPU Usage", select a range in the graph (or just "Select View" to select all), preferably turn on "Load Symbols" and then select "Summary Table".
The information you get look like this:
To be fair to LatencyMon: Xperf likely wont give you any further informations about ACPI Interrupts either. On my bootcamped MBP the only information I get is that "ACPIInterruptServiceRoutine" is called whenever ACPI.sys issues an Interrupt (there are no DPCs for ACPI.sys on my machine, only Interrupts).
But since ACPI is one of the few (if not only) parts where Windows still needs the BIOS, it is safe to assume it is a BIOS problem when ACPI.sys turns out to be a performance culprit.
Version 2.0 of LatencyMon has just been released:
http://www.resplendence.com/latencymon
Hey there, hope I can help many of people experiencing latency problems with soundcards.
I purchased the Babyface but had huge problems with latency and was unable to set buffer size below 1024 in order to get rid of cracks, pops and dropouts, which was ridiculous especially because I have a top high end PC (I7 980 6c, Win 7 64...)
I mainly work with Sonar 8.5, as a DAW but knew it wasn't the cause, for I had problems outside of it. I feared an incompatibility problem with my Nvidia Quadro FX 4800, or my Cintiq 21 UX, or whatever... (spent the whole night figuring it out)
Then I downloaded dpclat (http://www.thesycon.de/deu/latency_check.shtml) to check about my latency and saw that I had huge red peaks every second (and a message saying I'd be unable to use the PC in real time). Obviously tried to deactivate one by one everything as adviced, but no success! And suddenly, I found what caused the bug:
Simply a small utility software installed with my Asus motherboard: PC Probe II. (scans temperature inside the PC to adjust automatically fans rotation speed). Right-clicked on the icon on the bottom right of windows and quitted, everything runs perfectly!!! 
)))))))
Now I run the Babyface at 64 samples buffer size in Sonar 8.5 on Win 7 64 bits (a lot of huge VST plugins and all you can imagine...) without any latency delay, and with a crystal clear sound. Actually the best I've ever heard!!!
You guys at RME are amazing, so, many thanks to everyone involved, your products rock!
This is the first time I can play piano or my guitars in Guitar Rig 4 in perfect real time. RME products are definitely the must-have! And the Babyface is awesome!!! (the Totalmix software is just a bit tricky to comprehend at the beginning, not intuitive at all, but I don't really use it, doing everything in Sonar. I'm sure it could be simpler, but, don't want to be killjoy there, cos' I'm so thrilled with my new baby!) Es ist wunderbar !!!
Anyway, if this helped you, thanks to share the information, for I've spent the night reading forums and seen many people with problems like mine, and found no one who thought about this kind of small utility software.
Cheers,
Man. (France)
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