Render problems

[Timefreak]

I'm having render problems on most of the servers eu and us.
-World holes
-missing blocks
btw I'm using the default texture pack

 

[Syranita]

I had on my old computer if i ran to high graphic settings, after optifine and lowering some graphic settings it helped, on my new one i got 2 days ago, there isn't any.

 

[Timefreak]

I've got a new pc which can do far on all other servers and changing my settings doesn't help for me