Using SODIMM DDR2 module on Cyclone 3

The PLL-feedback was supported in earlier versions of Quartus and for CycloneII and StratixII. I just checked the MegaWizard and for CycloneIII Altera chose to 'only' deliver the 'advanced' solution (ALTMEMPHY ...). But you're right, doing the PLL approach from scratch will be a big project.

The EP3C40F484 has 16 DQSx8 groups, so rws28 should be able to implement his DIMM interface just using 2 sides, because, to my idea, he can use the non-DQ pins to supply command and address to the DIMM. That would leave the 2 other sides for interfacing logic with a different VccIO voltage.