This isn’t really a future suggestion. It’s inevitable that mIRC will eventually start offering a 64-bit version. Since mIRC
is compiled via visual studio, it can already be compiled in 64-bit mode. That being said, there are no real merits to accelerate this process. IPv6 is already supported and as for the speed boost, mIRC will probably perform faster on 32-bit anyway. This due to the fact that most operations are done on small buffers (due to many inherit limits like line/irc/vars/etc), moving to 64-bit will probably hinder performance a little (not too much) due to the fact that on-chip cache will be exhausted quicker. Of course only a profiler could validate that assumption.
