"LPM_MULT" Modelsim simulation problem

I want to use the dedicated multiplier but reluctant to use ip core, which generates too much files, so writed the vhdl code. I don't think the declaration of LPM_MULT is the key question. The key problem is the LPM_MULT doesn't work in modelsim, but has no problem in quartus. By the way, how to check my LPM_MULT port is right or wrong? my quartus version is 8.1 and modelsim version is 6.5a .thanks for your reply