It's all in the time----ing...
1. When I have an empty project with no recordings playing back (and thus no disk access) my MIDI timing is rock-solid sampleframe accurate. This is MIDI either being played back from the sequencer or being passed through to an external device. (I'll grant that the latter is hard to test, and I'm more or less just going on feel.)
2. The more tracks I add to the project, the worse the timing gets, and by the time I'm up to my normal track count for an instrumental (which is 30 to 50 stereo tracks) the MIDI timing is so bad as to be essentially useless. Here is an example. What you're hearing is 32nd notes fired every 16th from the DAW to an MKS80, and recording the result. The only way I can get it that good is to open my buffer all the way; I normally run it at 64, but with it set that low, maybe 5 of those notes will trigger, and in the wrong spot, natch. That's at the AES16's highest buffer setting, 1024.
So that's what's happening. The rig is Cubase 4 on Vista Business, on an Athlon64 machine. The audio is streaming off a half-TB RAID 0 array, and the MIDI interface is a MOTU MIDI Express 128. I have tried all the usual methods of getting Cubase to comply; you can rest assured on that account. I've been using PCs for music for over a decade, and Cubase almost that long. I know how to run and tune this rig; this is why this particular issue is giving me some trouble, as it falls outside my experience.
In any event, it is obviously related to the disk streaming. The more audio that is getting played back from the DAW, the worse the timing. Anyone run in to this before? If so, what's the fix?