My PCB has a 2.0mm pitch 10pin JTAG header (2x5). My MIPS programmer has a common 14-pin(2x7) 2.5mm pitch socket connector header at the end (flat IDC cable with female header). How do I interface them? Is there special Breakout Board adapter for this?
These are commonly called "pitch changer" adapters. You may or may not be able to find one that suits your needs. If you can't find one, you can make a suitable cable yourself. All you need is a piece of ribbon cable, the sockets for either end and the appropriate crimping tool for whatever sockets you choose.