As DP fans since it's first release, we disscussed this subject on the french forum .
Tests had been made by a large amount of DP4 and DP 3.xx users with 2408, 1224, midi express etc...and a lot agree that Motu has been unable to resolve this basic problem. On top of that, we have to admit that Motu's tech support really treat us like a..holes by never replying.
We avoided using words like latency, extensions, interfaces, time stamping or any other configurations. Why? Because It's all about sloppy midi precision when using buffer 256 to 512.
There's no sharp presision with ANY midi devices and too much offsets throug out a sequence of 10 mesures. If buffer 64 is best to have midi precision, then what's the interest of having a Dual G4 monster? A silly groove box is much more precise.

OSx's Audio unit or Midi core has nothing to do with that unless you have problems with audio streaming, bussing, patching or plugins or read/write disk.
PLEASE take 5mn to do this HORROR TEST with only 1 midi track and 1 audio track:

1- Program a short closed 16beat hihat sequence with an external AND midi device of your choice during 10 mesures. Use velocity64 and decay64. make it as clean as possible.
2- Record your hihat during those mesures at tempo of your choice.
3- Open the audio edit window and zoom until you reach 30 ticks steps. You see better with vertical lines.
4- Edge edit the first beat of your soundbite and make sure to stick it sharply on the vertical line. Your
first recorded hihat should start at 1/1/000.
5- Scroll side ways on each 16 beat through out those 10 mesures. You can also use markers per beat to
switch quickly and see the desaster on your screen.
6- Repeat the test using different buffers and/or different devices. Try it even with the Mac's internal click.
7-send an e-mail to Motu tech support.
8-If they don't reply, send the same one 30times. same result.

To be honest, we called the official dealer in France and admitted that there is a serious problem that
enables all users to switch from Motu to Emagic.

PLEASE take 5mn to do this test so we could save Motu as much as possible. Can someone proove the contrary at buffer 512?

Marc