DPC Latency Checker
DPC Latency Checker is a Windows tool that analyses the capabilities of a computer system to handle real-time data streams properly. It may help to find the cause for interruptions in real-time audio and video streams, also known as drop-outs. The program supports Windows 2000, Windows XP, Windows XP x64, Windows Server 2003, Windows Server 2003 x64, Windows Vista, Windows Vista x64, Windows 7, Windows 7 x64.
any kernel-mode device driver in your Windows system is implemented improperly and causes excessive latencies of Deferred Procedure Calls (DPCs) then probably drop-outs will occur when you use real-time audio or video streaming applications. For an explanation of this effect see Background information below.
The DPC Latency Checker tool determines the maximum DPC latency that occurs on your Windows system and thus enables you to check the real-time capabilities of your computer. DPC Latency Checker works independent of any external hardware. Using this tool may be helpful in the following situations:
1. You experience interruptions (drop-outs) in a flow of data processed in real-time, for example an audio stream, video stream or a sequence of measuring data, and you want to find out the reason for this problem.
2. You want to verify that your Windows system is configured properly so that it is capable of handling real-time data transfer before you install the corresponding streaming application.
3. You want to check if a particular computer system is suitable for streaming applications, for example before you buy this system.
DPC Latency Checker is very simple to use. Download dpclat.exe and launch it. No software installation is required.
DPC Latency Checker periodically updates its internal statistical data at an interval displayed as Test Interval. This statistical data is queried and displayed on screen once per second. The Current Latency value indicates the maximum DPC latency measured within the last second. The value labeled Absolute Maximum represents the maximum latency measured since the tool was started. Use the Reset button to clear this value.
The bar graph shows the Current Latency value over time. Each bar represents the maximum DPC latency occurred within one second. The most recent value is shown as the right-most bar. Every second, bars are scrolled from right to left and a new bar is added at the right-hand side.
Latency analysis can be stopped by means of the Stop button. If the button is clicked again the tool restarts measuring of DPC latencies.
You can find out the driver which causes the excessive DPC latencies by disabling individual devices using Windows Device Manager. To open Device Manager, choose Properties from the context menu of the My Computer icon on your desktop and click the Device Manager button on the Hardware tab.
After you disabled a single device, carefully watch DPC Latency Checker. When excessive latency values disappear you found the responsible device driver. If there are still exceptional large DPC latencies try the next device.
In many cases DPC latency problems are caused by specific types of devices. So you should try the device types listed below first.
* Network adapters for Ethernet and Wireless LAN (W-LAN)
* Internal modems
* Internal sound devices (on-board sound systems)
* Any PCI or PCI Express add-on card, any PCCard or ExpressCard, e.g. TV tuner cards, ISDN or DSL adapters, modems, etc.
Warning: Don't disable devices that are essential for your computer to function!
You should not disable:
* any device listed in Device Manager under System devices or Computer,
* the hard disk that contains the system partition,
* the IDE/ATAPI or SATA controller this hard disk is connected to,
* the system keyboard,
* the mouse, track point or touch pad device,
* the USB controller external keyboard and/or mouse devices are connected to,
* the display controller listed under Display adapters.
When you have identified the device driver which is responsible for the drop-outs consult the device vendor's Web site or customer support to find an update for this driver. If this is not possible you may decide to keep the concerned device disabled while you are using streaming applications.
By using the method described above, in some cases it may not be possible to clearly identify a device driver that is responsible for the problems. In such a situation you could try to use the tool RATT available from Microsoft. However, RATT is not easy to use and analysis results might be difficult to interpret. To download RATT, search Google for "Microsoft RATTV3".
The license of this software is Freeware, you can free download and free use this diagnostic software.