I believe it's set to 1000 blocks (based on out-of-context IRC conversations).

 

This would explain why my 11x23 4-floor farm was more effective than a 200x200 farm. I knew I wasn't insane. D:

And even though 200x200 several-floor farms can be broken up into smaller ones... They are a lag fest. ._.

 

You had those problems before the 200x200 farms wouldn't grow right >.>

 

..what problems? o_O Lag? Any farm more than 50x50 has always caused lag or other buggy issues. A one-layer 200x200 farm drops my FPS anywhere from its average (60-70) to about 15-30. :/ Growing or fully grown. The ones that have been farmed and not brand new seem to be laggier. And any that I have been in that is more than one layer drops my FPS to an average 10, lol.