If you are talking about an intensive processor, its a rather relative term, however. NET is not, but ASP.NET. Web applications that perform thousands of postbacks and recreate / destroy controls for each request are quite expensive.
Think about it this way, in pure ASP.NET (not ajax, old) calculate the visibility / color .. all the attributes of each element of the html page for 1000 users only on the server and distribute them to clients. Not only do these poorly written ASP.NET server controls consume more processor, as they do too much computation.
To improve ASP.NET performance, you need to use AJAX or use RIA, since Flex / Silverlight will drastically reduce the load on the processor, because you can use the client processor to visualize the data.
RIA Client (Flex / Silverlight) + ASP.NET Web Services is the future, I do not have detailed statistics for sharing, but we moved away from ASP.NET almost a year ago, and our CPU usage was reduced to 18% from an average of 99 % to RIA-based websites.
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