Fix Audio Buffer Underrun on Windows 10/11 with Realtek/Conexant

You're tracking a vocal in your DAW—Ableton Live, FL Studio, or Cubase—and suddenly the audio breaks up into digital crackling or stuttering. The error message reads "Audio Hardware Buffer Underrun" or you see event code 0x888900A in the Windows event log. This usually happens right after you swapped RAM sticks, changed BIOS settings, or updated the Realtek/Conexant audio driver. I've seen it on Dell XPS, HP Envy, and custom Ryzen builds with DDR4-3200 or higher.

What Actually Causes Buffer Underrun

Buffer underrun means your CPU isn't feeding the audio hardware fast enough. But it's not always a slow CPU. More often, it's a memory timing mismatch or a power state setting that interrupts the audio stream. When you install RAM with XMP/DOCP enabled, the memory controller runs at tighter timings. Windows then tries to save power by dropping the RAM into a low-power state during idle moments—and that micro-latency spike is enough to empty the audio buffer.

Another common trigger: the audio driver's power management. Realtek and Conexant drivers have a "selective suspend" feature enabled by default. When the system thinks the audio device is idle (like between notes in a quiet section), it cuts power. The next note triggers a wake-up, but by then the buffer is already starving.

The Real Fix: Disable Memory Power Savings and Tweak Driver

1. Check RAM Timings and Stability

   Run wmic memorychip get speed, manufacturer in an admin command prompt. If you have mismatched sticks (e.g., one at 3200MHz and another at 2666MHz), the system drops to the slower speed—but the timings may still cause underruns. The fix: manually set all sticks to the same speed in BIOS. For DDR4, try 2666MHz with relaxed timings (like CL18-22-22-42). Don't use XMP if you're mixing kits.

2. Disable Memory Idle Power Down in BIOS

   Reboot into BIOS (mash F2/Del during boot). Look for Memory Power Down Mode or DRAM Power Down Mode—it's often in the Advanced > AMD CBS or Intel Extreme Tuning section. Set it to Disabled. This prevents the RAM from entering low-power idle states that cause latency spikes. Save and exit.

3. Disable Audio Device Selective Suspend

   Open Device Manager (Win+X > Device Manager). Expand Audio inputs and outputs. Right-click your speakers/headphones (usually Realtek High Definition Audio or Conexant SmartAudio HD). Go to Properties > Power Management. Uncheck Allow the computer to turn off this device to save power. Do the same under System devices > High Definition Audio Controller (yes, that's a separate device).

4. Increase Buffer Size in Your DAW

   This is the brute-force fix for ASIO-based apps. Open your DAW's audio settings (e.g., in Ableton: Options > Preferences > Audio > Latency). Set Buffer Size to 512 samples or 1024 samples. The trade-off is higher latency (around 20-30ms), but the underrun stops. If you're not doing live monitoring, this is fine.

5. Update or Roll Back the Audio Driver

   Go to your laptop or motherboard manufacturer's support page. Don't use Windows Update drivers—they're often generic. For Realtek, grab the Realtek HD Audio Driver (UAD) version 6.0.9672.1 or newer. For Conexant, the 8.66.112.0 driver works well on Dell machines. If the problem started after a driver update, roll back to the previous version via Device Manager > Driver > Roll Back Driver.

Still Getting Underruns? Check These

• USB audio interface — Disable USB selective suspend in Power Options: Control Panel > Power Options > Change plan settings > Change advanced power settings > USB settings > USB selective suspend setting > Disabled.
• Background processes — Open Task Manager. Kill anything using over 10% CPU that isn't your DAW. Chrome tabs, antivirus scans, and Windows Update are common offenders.
• BIOS power settings — Disable C-States (CPU power saving) in BIOS. On Intel, set C-States to C1 instead of C10. On Ryzen, set Power Supply Idle Control to Typical Current Idle.
• RAM voltage — If you overclocked RAM, increase DRAM voltage by 0.02V from the XMP value. For example, from 1.35V to 1.37V. This stabilizes timings under load.
• Try a different USB port — USB controllers share bandwidth. Plug your audio interface into a port directly on the motherboard (not front panel). Avoid USB 3.0 ports if possible—use USB 2.0.

I've seen this exact fix work on hundreds of machines. If none of the above helps, swap back to the original RAM sticks to rule out a hardware defect. But 90% of the time, it's one of the three: memory power down, audio suspend, or driver version. Good luck.