Modelsim-Altera very slow

http://www.altera.com/products/software/quartus-ii/modelsim/qts-modelsim-index.html

You may be running into the design size limitation, which severely degrades performance. In newer releases, there will be a message in the console transcript to that effect if it is indeed happening to you.

Depending on what you are debugging, one tip to speed up debugging is to not use full frame sizes; use something small like 64x64