DPC-X User Guide

What DPC-X is, and who it is for

Every driver on your PC (graphics, network, USB, the firmware itself) takes small turns inside Windows before your music software gets the processor back. When one of them takes too long, you hear it: a click, a short cut, a dropout. That waiting time is called DPC latency. It happens on fast, modern PCs too, and it has nothing to do with how powerful the machine is.

DPC-X does three things about it:

• Measures which driver is the one that gets in the way, using the measurement built into Windows itself. You get a report that names the driver, not a guess.
• Isolates that driver, and the usual suspects, away from the processor core that your audio uses.
• Looks after your audio while your music software runs: full processor speed, high priority for your program, background tasks paused. The moment you close it, your PC is back to normal.

Before you install

DPC-X changes system settings: how interrupts are shared between processor cores, the power plan, the timer precision, and a few Windows services while your music software runs. It records your PC's original state the first time it runs, and Restore original puts everything back whenever you want.

Even so, it works on your system. Two minutes of preparation are worth it:

1. Create a Windows restore point. Press the Windows key, type Create a restore point, open it, click Create. A restore point is always the safest way back, whatever happens later.
2. Connect your audio interface and have your music software installed. DPC-X needs to see the interface to know which core it uses.
3. Close your music software while you install and optimize. You will open it again when everything is in place.

Installing

1. Download the installer from pablomartin.com/dpcx and run it. It asks for administrator rights once.
2. Read and accept the license agreement. It is shown in your language where the law requires it.
3. Let it finish. The installer puts DPC-X in Program Files, installs the DPC-X ASIO driver, and starts a small background service called the guardian. The guardian is what watches your audio while you play; it starts with Windows and uses almost nothing while it waits.
4. Tick Launch DPC-X at the end, or open it later from the desktop icon.

The panel opens with the Status page, a live meter of your PC's latency. Leave it there for now: the next section is the one that matters.

DPC-X ASIO: the step that matters

Your music software talks to your audio interface through an ASIO driver: the driver that came with your interface, for example the one from RME, MOTU, Focusrite or Universal Audio. DPC-X adds a driver of its own, DPC-X ASIO, that sits in front of yours. Your music software talks to DPC-X ASIO, and DPC-X ASIO talks to your interface's driver. Nothing changes in the sound, the latency or the settings of your interface. The only difference is that DPC-X is now inside your audio, where it can do its real work:

• It knows the exact moment your music software starts and stops using audio, so the guardian can switch your PC into its best state at the right time, and back again when you are done.
• It keeps your audio on its dedicated processor core, at the highest priority, away from everything else.
• It measures every single audio callback, so when something goes wrong the report can say what it was and which driver caused it.
• If your interface's driver stops answering mid-session, it asks your music software to reopen it instead of leaving you with silence.

Setting it up (once)

1. In the panel, open Settings.
2. Under ASIO proxy, if it says The proxy is not registered, click Install proxy. The installer normally does this for you.
3. In the Driver list, choose the ASIO driver of your audio interface and click Use. The panel now says The proxy wraps: followed by your driver's name.
4. Open your music software, go to its audio settings, and choose DPC-X ASIO as the audio device. Set the buffer size you normally use.

That is all. From now on, every time you open your music software, DPC-X knows, and the guardian takes care of the rest. In the panel, the Status page shows your program's name and a live reading of how your audio is doing.

Optimize

Optimize is the one button that tunes your PC. Open the Tweaks page and click Optimize. With your music software closed, DPC-X then:

1. Measures your PC as it is now, for about three minutes. Leave the PC alone during the measurement: do not play, do not download.
2. Records your PC's original state, so it can always go back.
3. Applies the settings that give audio the best chance, and moves the drivers that the measurement caught in the act away from your audio core.
4. Asks for a reboot. Some of the changes only take effect after one. Click Reboot now when you are ready; until then the panel reminds you with a banner.
5. Measures again two minutes after the PC comes back, and writes a report comparing before and after.

You can run Optimize again whenever you like, for example after a driver update or a new device. It always compares against the original state it recorded the first time, never against a previous optimization.

While you play

Every time your music software opens its audio through DPC-X ASIO, the guardian starts a session. For as long as it lasts, your PC runs in its best state for audio: full processor speed, your program at high priority on its own cores, background services such as Windows Update and search indexing paused, the PC kept awake. When you close the program, everything goes back to normal by itself. There is nothing to click.

The tray icon tells you how the session is going at a glance:

• Green: all good.
• Amber: something took longer than it should, but your audio did not suffer.
• Red: your audio was late. The Status page and the log say which driver did it.
• Grey: the guardian cannot measure right now (for example while another measurement tool is running).

A balloon from the tray tells you when a spike happened during a session. You can turn that off in Settings if you prefer silence.

The panel

Closing the window does not stop DPC-X: it keeps running in the tray, and the guardian keeps watching. Double-click the tray icon to open the panel again.

Reading the report

A report has one line that matters, at the top: the verdict. Excellent and Good mean your PC is in good shape for audio. Fair means it will mostly work, with the occasional click at small buffer sizes. Poor means a driver is seriously in the way.

Below it, the report names the drivers that caused the longest delays, in order. The name tells you where to look: a graphics driver, a network adapter, a USB controller, the motherboard's power management. When Optimize could not do enough, the report says so, and names the driver you should update, replace or, if you do not need the device, disable in Windows.

Everything else in the report is detail for when you want it. You do not need to understand it to use DPC-X.

Going back: Restore original

On the Tweaks page, Restore original returns your PC to the state DPC-X recorded the very first time it ran, however many times you have optimized since. It asks for confirmation, and for a reboot when one is needed to finish.

Restore original undoes what DPC-X changed. It does not undo other things you may have done to your PC in the meantime; for those, your Windows restore point is the way back.

Uninstalling

1. First, click Restore original in the panel, so your PC is back the way it was.
2. In your music software, choose your interface's own ASIO driver again instead of DPC-X ASIO, and close the program.
3. Uninstall DPC-X from Windows Settings > Apps. This stops and removes the guardian, removes DPC-X ASIO, and removes the start-with-Windows entry.

Your reports and DPC-X's record of your PC's original state stay in C:\ProgramData\dpcx, so a later reinstall can still put the machine back. Delete that folder if you want nothing left.

Troubleshooting

Support