I find it hilarious when people complain about any mod like rotarycraft causing 'lag', when the irony is the actual reason for the 'lag' isnt anything to do with the mod itself, it's actually, surprise surprise, just minecraft's own code and design. 2 main parts to be specific;
- rendering, minecraft uses OpenGL1.1/1.2 (or at least in 1.6.4), the latest actual release is 4.5, openGL 1.2 was released 1998 and 99.9% of graphics hardware suitable of running games as small as minecraft support a bare minimum of openGL 3.2, all in all the main issue with this is minecraft _has no vertex shaders_. what does that mean? it means every single triangle in the game has each of it's 3 points calculated on the CPU and then sent to the GPU one-after-the-other. this takes absolutely ages in render terms, modern GPUs can process billions of vertices in complex shaders whereas any modern CPU will always struggle with less than a million.
- chunk updates, whenever a block or tile entity updates itself and sends data to the client, the code behind it involves un-wrapping, performing a 3-dimensional map-lookup and then un-wrapping the actual data to be force-applied to the tile in the client, sure doesn't sound too bad does it? not when you're updating hundreds to tens of thousands of them. One common discovery is that you don't get these lag issues in singleplayer, yet on a dedicated server your FPS might be a quarter or less of what it was just due to this alone. and/or the game will run super-stuttery.
at least in 1.7 mojang are actually trying to fix both of these in some way, however rendering will likely always still be slow unless they actually add a proper modern render pipeline with proper asset management. Such a thing however was something I was debating to have in the coremod of another W.I.P. mod I was working on, however it'll likely mean a lot of vanilla code changes and I just don't have that time atm for the mod itself let alone that, if anything it'll have to wait for about ~6 weeks minimum when my academy work drops off...
anyway if anyone 'needs' a simple power conversion mod for 1.6.4 (not sure when Ill update it atm) that doesn't contain any loss bugs, or if people might want to look at it's source;
http://forum.feed-the-beast.com/threads/1-6-4-power-inverters-mod-early-alpha.49496/