some Xbox Classic games (as Prince of Persia: The Two Thrones) emulated from Xbox 360 RGH suffer video jerks. I thought they were emulation problems.
But something disconcerting has happened to me with "OutRun2". This game works very bad, video jerks, menu jerks, slow loading and finally graphical corruptions in game. But surprisingly if instead of executing it from the internal HDD I do it from a USB pendrive or from the internal memory console works perfect.
So, I have also tried the Prince of Persia: The Two Thrones checking that from USB the videos do not suffer jerks either.
In short, some classic Xbox games (about 5 out of 34 that I have tried) do not work well from internal HDD, but yes from USB. With Xbox 360 games I have no problem from HDD.