written by: Finn Orfano•edited by: M.S. Smith•updated: 6/14/2010
A look into why CPU usage sometimes spikes when downloading bittorrents.
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It’s not uncommon for someone to ask why does CPU usage spikes when downloading torrents, and there are a variety of answers for that question. The reason why there isn’t just one answer is because of all the variables to consider. It could be something to do with your router, or maybe a software issues involving your firewall or security programs. In this article, I’ll explain how bittorrents work and possible causes for CPU spikes.
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How Bittorrents Work
The proper name for a torrent is actually bittorrent, but it’s acceptable to call them either. Bittorrents are a form of P2P (peer to peer) networking, which means that files are shared between other people who have the files, and those files are not stored on any one network location. When you download a file from a website like Download.com, for example, you are downloading the entire file from a server that hosts the site. Bittorrents work in a completely different manner than a direct download from a website.
With a torrent download, instead of getting the actual file from a single source you download bits (literally and figuratively) of the file from a multitude of sources, depending on how many seeders are out there with the same files. Seeders are what you call people who have the complete file and upload to those who need it. For more information, check out this great article on how bittorrents work.
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CPU Usage Spikes with Torrents
Although my previous explanation of how bittorrents work is extremely oversimplified, it at least should give you a general idea of how they work. With that in mind, I hope it also helps to explain why your computer’s CPU gets hit pretty heavy. When you download a popular bittorrent where there may literally be several thousand peers and seeders, you have to realize that your computer is actively communicating with all of them to find the best download rates, file sources, and so on. This is where the ‘torrent’ part of bittorrent gets its name.
If your CPU usage is hitting 100% for any reason, you should go into the Task Manager and see what program is taking up all the CPU time. In the case of downloading torrents, it could be anything from your bittorrent client to some kind of security software. You may consider disabling your firewall while downloading a torrent, but do so at your own risk.
When your computer is managing a torrent of data coming across the network connection and writing a lot of that information to the hard drive, you can expect decreased performance in other operations. Depending on what kind of security software you use, such as a firewall that checks incoming and outgoing connections, there could be some delays as all that bittorrent traffic is analyzed. Depending on the number of files being download, as some torrents may be on large file or hundreds of smaller ones, your virus scanner will want to check all that data and it cause also cause a CPU usage surge.
Another thing to look at is your bittorrent client, and by that I mean the program you are using to manage the torrent downloads. A variety of them are available and they are updated often, so you may want to try another client if yours is causing problems. You may also want to check for updates to the one you are using. I recommend using uTorrent because it updates itself regularly, and I’ve had no problems with CPU usage spiking no matter how many downloads I have going at once.