I have been running mIRC on the same computer for ~8 years now. As far back as I can remember it has been using a surprising share of the CPU time. I'm on many networks and quite some channels though. This is a server that has some other things to do, and recently it has been assigned some more real-time critical jobs that suffers because of mIRC constantly using 20-50 % of the CPU (average % over a longer time is 25-30).

The CPU is an AMD Turion II Neo @ 1.5 GHz (dual core). 4 GB of RAM (but seldom using allocating more than 50-75 % of it). System/mIRC disk is a fast SSD on SATA-II in AHCI mode (disk access is very low). Operating system is Windows 2019 Server (Datacenter edition, 64-bit), things were the same with Server 2012 R2 and 2008 R2. Using the integrated GPU or an Nvidia Geforce GT710 makes no difference.

Memory, disk access and network traffic are never close to being bottlenecks and mIRC uses very little of them, it is just the CPU time that is the problem. The mIRC GUI is also rather unresponsive and switching channel windows , typing in the input field or scrolling in backlog has noticeable lag, from fractions of a second to several seconds until a response is seen (not response to running a command, just showing what I type). This happens even when the CPU is not running at full load, other programs run fine.

I am looking for help in what I can do to make mIRC use less CPU, and hopefully also make it more responsive, without crippling it by lowering the process priority.

I am on ~55 channels over 22 networks, none of the channels have any real heavy traffic.

What I have done already is that I have removed all scripts, all DLLs, all aliases, all user variables, cut down on logging, looked through all settings to find settings which I could suspect slow things down (mostly Windows GUI interactions like desktop windows, "tips" and animations, but I might have missed settings that I don't understand fully!?) and tried a clean install in portable format. Nothing has made a noticeable difference. I have read about others who had problems with mIRC using all CPU specifically when they were using scroll bars or similar, but I have not been able to replicate such a problem here. I have experimented with the /fupdate setting (0 or 100) without any improvement.

If I run mIRC without any server connection and without opening up the server/channel windows, it uses 0 %, even if the application is focused. I can push it up a few percent if I interact with it.

If I have all my usual server/channel windows open but disconnected and with mIRC still open and in focus, mIRC uses 18-22 % CPU most of the time, but jumps up to 45-50 % 3-4 times/minute, over time average is ~25 %..It is still clearly unresponsive and jumps up to 45-50 % much more often when I type in the input field. Keeping mIRC minimized in this state lowers the CPU use by 1-2 % only, with the increases to 45-50 % occurring 2-3 times/minute, average use ~22 %.

So, what can I do? Is it possible to use mIRC with my number of networks and channels without the heavy CPU use? Is there some way I can troubleshoot things and see what it is spending all this processing power on? Do you have some general good advice for settings or other things that might help me?