Re: Windows 10 release 1803 (build 17134.285); fatal DPC Latency problems. Issue with Sept MS Win10 update?

Simon Brown

Check the audio playback driver.


Simon Brown, G4ELI



From: <> On Behalf Of Cormac EI4HQ
Sent: 23 September 2018 19:44
Subject: [SDR-Radio] Windows 10 release 1803 (build 17134.285); fatal DPC Latency problems. Issue with Sept MS Win10 update?



A heads up. I've been running most recent versions of SDR-Radio up to and including version 3.03, build 1263 (September 11th) on a specific Win10 PC since last November. The system has been rock solid, running circa 12 hours in every 24 to decode Navtex (two receivers, audio into 3rd party software) while simultaneously also recording 16bit I/Q data (384KHz bandwidth) for later offline DGPS decoding. This setup has been put through its paces and has performed solidly for an extended period. Only the SDR-Radio version has been changing as Simon has released updates, and windows updates were done as they were released. This setup purred along for almost 12 months.

About 2 weeks ago something went bad, very bad. The PC, by then running Windows 10 (1803 including the September updates from Microsoft) developed complete show-stopper DPC latency issues; stuttering on the audio initially but very quickly causing the entire PC to bog down and freeze in short order. The stuttering was happening not just with SDR-Radio and the AirspyHF+ but also if I ran SDR# and the AirspyHF+, SDR-Radio and an SDR-IQ or Spectravue and the SDR-IQ. Same result - after about 5 minutes of trouble free operation, stuttering starts - the audio latency time indicated by SDR-Radio begins to climb, as does the CPU load - it increasingly rapidly - and then performance just collapses in a cascade type failure. Running other apps that depend on streaming audio e.g. Spotify results in the same outcome.

The past two weeks have broken me as I tried to sort it out but to no avail. I tried everything I could think of, driver roll backs, disabling hardware, hundreds of subsets of services combinations, stripping back peripherals including even the keyboard, mouse and display at one point. Lately I've been spending hours pouring over Windows Performance Analyzer data (part of the Windows Assessment & Deployment Kit) to try and figure out what was happening - I'll confess to being a total novice in that regard but while I could see the consequences of the DPC delays when they kick off, I couldn't figure out the cause.

In the end I gave up. Today, I've done a completely clean installation of Windows 10 (1803 build 17134.285) on the same hardware and installed nothing but SDR-Radio and my AirspyHF+. Unfortunately, the DPC latency issues are there with this shiny, new and clean setup and occur exactly as they did on my previous installation. Something has gone wrong somewhere and I can only think of two possibilities; a partial hardware failure on my PC (bit of a stretch I think) or something has gone wrong with Win10, possibly introduced in the September updates... If anyone else has other ideas, I'm really keen to hear them because as things stand, I'm dead in the water just now.

Lots of searching online suggests issues of this nature i.e. DPC latency issues with Win 7,8 and 10 are usually quite hardware (driver) combination specific, so many will likely be unaffected but some of you might so just a word of caution in case...

My hardware: Zotac ID-90-Plus. i7 2.5GHz, 16bB RAM, 250gB SSD, x2 Realtek PCIe GbE Family ethernet (wifi and Bluetooth adapters disabled), Intel (R) HD 4000 graphics, onboard HD Audio (MS driver), USB3.0


Cormac, EI4HQ
[Cork Harbour / UTC+1] NNNN++++

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