The highest number of units present in-game is about 200, and I do not recommend trying this on weak computer because even that was causing an even catastrophic consequences for your computer (BSOD).
There is a thread already about this issue, but it's too old. I guess it might happened on all versions of Warcraft III, including Reforged:
if too much unit spawn more than 200 it will make lag...how to fix this?spawn more than 200 but never lag how to do it?help me please
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