user323: I am running the standard client on a micro Amazon EC2 instance. When I am synchronising Bitcoin with the network, it uses about 50% of the available CPU. After it is fully synchronised, I leave it alone and it cranks up to 100% by itself.
What can be causing the standard client to behave in this manner? Is it due to possibly high transaction volume, sharing information with peers, or perhaps something else?

user6080: No, according to the information on small and micro instances at this link.
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/concepts_micro_instances.html
Bitcoin.conf ( the Bitcoin Configuration file ) may have an option set to 1 to activate mining within the client software.  If you have it set as ' gen=1 ' it will try and ' generate ' coins ( mine on it's own ) and that drives CPU usage up.  Also, according to the graphs on that link, it should not ' jump ' to 100 percent use, each instance should drop down to a low usage level for small and micro Amazon EC2 instances.  There may be other programs running on your Amazon EC2 instance that can also drive up CPU usage so I recommend checking your files starting with looking for any instance of Minerd ( cpu miner ) and removing it. 

323: <p>I am running the standard client on a micro Amazon EC2 instance. When I am synchronising Bitcoin with the network, it uses about 50% of the available CPU. After it is fully synchronised, I leave it alone and it cranks up to 100% by itself.</p>

<p>What can be causing the standard client to behave in this manner? Is it due to possibly high transaction volume, sharing information with peers, or perhaps something else?</p>
 6080: <p>No, according to the information on small and micro instances at this link.
<a href="http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/concepts_micro_instances.html" rel="nofollow">http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/concepts_micro_instances.html</a>
Bitcoin.conf ( the Bitcoin Configuration file ) may have an option set to 1 to activate mining within the client software.  If you have it set as ' gen=1 ' it will try and ' generate ' coins ( mine on it's own ) and that drives CPU usage up.  Also, according to the graphs on that link, it should not ' jump ' to 100 percent use, each instance should drop down to a low usage level for small and micro Amazon EC2 instances.  There may be other programs running on your Amazon EC2 instance that can also drive up CPU usage so I recommend checking your files starting with looking for any instance of Minerd ( cpu miner ) and removing it. </p>
