Tim. I have no merit. I fly these planes as is.
Difference?  My CPU is 3.1 I run Windows 7 Ultimate 64 bits, I have 16G of ram and I stay in FSX.
Try this I am curious ! Do a flight plan and create an ED.
It should show in Vnav page 3.
When you are about 150 from destination, go to Vnav/3 and punch
Desc now.  See what happens ! This should initiate a shallow descent
-1250, and when you reach the regular descent path intercept, the plane should now follow the projected path.  What if?

Desc Now can only be done within 50 of the TD. 150 should be close enough. The aircraft is in fact under the TD to intercept somewhere in front.   ::)

The CRZ page header should change to  CRZ DSC - also saves a little fuel.

Raymond   Boeing or nothing
KFLL    South Florida