Semaphore Timeout Period Has Expired, Error 0x80070079

A “semaphore” is a type of programming object used in multi-threaded processing across networked devices. The semaphore timeout tends to happen when copying large amounts of data to external hard drives or networked machines.

What is semaphore?

The word ‘semaphore’ comes from a communication technique that is like visual Morse code. Flags are waved in different positions to designate letters of the alphabet visually over great distances.

Why use such an obscure word in a computer program?

Well, semaphore is actually a clever word that can help us visualize the process the computer is performing.

Think about the opening credits of “Top Gun” where the aircraft carrier’s landing signal officers wave their arms around in cool positions while singing, “highway to the danger zone”.

Now imagine the scenario where one aircraft carrier is sending all of its jets over to another aircraft carrier and the signal officers need to coordinate landing the jets and assigning parking spaces for each jet just by communicating with these flags. Before the next jet can take off the second ship needs to confirm there is a parking space by waving the flag.

No flag waving in the distance, no jets take off.

Two Navy men on Air Craft Carrier directing jet for take off.
U.S. Navy photo by Photographer Mate 3rd Class D. Keith Simmons. [Public domain]

But wait, there’s a problem, one of the flag waving semaphore experts on the distant ship is not responding.

Should the captain make the non-responsive sailor walk the plank? Maybe it is best to consider reasons beyond his control for not getting back to the other ship with its flag messages.  Should we assume the guy just fell asleep on the job? What if it’s foggy and it’s not his fault that his messages aren’t seen?

The semaphore in your computer program is the code that checks to make sure multiple devices are synched. This error is more common in Windows machines but the term semaphore is used in many programming languages.

WARNING! Semaphore Error may indicate the need to replace hardware.

Semaphore Timeout Period Has Expired, Error 0x80070079

This error message is symptomatic of a connection issue in most cases which is solved by looking at the wireless network or the connection cable, depending on your situation. It is possible that a device could have corrupt data which causes the error. In that case, troubleshooting can become much more complicated and it may be time to replace the device.

Most Common Scenarios:

Copying large amounts of data over a wireless network or copying large files using a USB cable seems to be the most common.

An enterprise may run into this problem while backing up large SQL databases. A single user might see this when copying large files to external drives.


How’s the network connection? How about the USB port and cables? Is the external device running out of free space?

It may be a lack of bandwidth in the wireless network or the wireless adapters need updating.

Helpful External Links:

Windows Network Adapter troubleshooting

Steps to update network drivers or disable firewall

External hard drive error troubleshooting

Here’s what programmers have to say at Stack Overflow

Related Gillware Articles

Enterprise Data Recovery

SQL Server Data Recovery

Enterprise Level

SQL Server Semaphore Error

Sometimes the Semaphore Timeout Error occurs while backing up SQL databases. There may be several nodes and only one of them has this issue. It is fairly common that companies will swap out that node for a new server in order to resolve the issue. If there is data on that device that is important to your business, our engineers may be able to recover your data from these machines.

Personal Computer

Semaphore Error copying files to a hard drive

Are you using an external Hard Drive that is actually at risk of failing and becoming unusable? If your hard drive is having any other problems this Semaphore error may be an early indicator of imminent failure. If you have gone through the troubleshooting techniques and still have trouble with your external drive it may be time you talk to one of our Client Advisors.

Our engineers see all kinds of failed drives, from thumb sticks to RAID systems. They have unique experience in diagnosing common problems you may be overlooking. We are in the business of recovering data and preserving data. I hope this article helps to understand what this error message means but I also hope to help prevent the loss of any data.

If you made it to the bottom of this article it is a good time to be reminded to go ahead and back up your important data across multiple devices.