Original sentence: FreeBSD (since 4.1) offers kqueue.IRCU coders have mentioned increases in the practical capacity per server from 10,000 users to 20,000 users.Linux offers this abilit in the form of epoll but this is a fairly new feature having appearedin the 2.5 development series (and therefore now availible in 2.6).Most of theese were writte primerilly for Microsoft Windows.Often theese are developed under the control of a very large irc network.Solaris has had /dev/poll since version 7.The difference made by theese new interfaces can be dramatic.The result is that the best platforms for ircds are those that offer effeciant mechanisms for handling huge numbers of connections in a single thread.Theese are usually easier to set up than hurried ports of unix ircds (especially cygwin based ports) and may perform better than those hurried ports.There have been other IRCDs developed from scratch, such as ConferenceRoom,ircplus ,beware ircd.Very few ircds are multithreaded due to the fact that nearly every action needs to access (at least read and possibbly modify the global state).running a large (more than a few thousand users) Irc server requires keeping a very large number of connections open for long periods
Edited sentence: There have been other IRCDs developed from scratch, such as ConferenceRoom which have primarily been designed to run on Microsoft Windows and is not open source or free (gratis)