Very strange behavior of Mixing Latency "Buffer Size" slider

I'm testing to see if Sonar 8.5 will run on a Dell D820 notebook computer with Windows 7. I realize that the sound hardware that is built-in (Sigmatel) is probably junk compared to real interfaces, but the computer can play decent audio into headphones from WAV or MP3 files. It is for experimentation, not a production mix. The computer has a 2GHz dual core CPU and can play 1080p video with AC3 audio smoothly, so it is not underpowered.

I set up a really simple test scenario with the 2 track MIDI sequence "2-Part Invention #13 in A minor", and the DreamStation DXi2 soft synth.  I got continuous clicking/dropouts in the audio. I tried both WDM/KS and MME drivers, but they behave the same. I've tried various settings, but the only thing that has an effect is the buffer size slider under Mixing Latency. If I put the slider as high as it goes (349mS), the rate of dropouts slows down. If I move the slider lower, the dropouts are faster.

By sheer accident, I discovered that when I set the slider to exactly 31.9mS (1408 samples), it works! No dropouts or clicks. Move it the slightest amount either way, and there are continuous clicks and dropouts.

Can anybody explain this? Is it only attributed to bad drivers from Dell and/or Sigmatel? Or is there some other setting in Sonar that could be involved?

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I'm testing to see if Sonar 8.5 will run on a Dell D820 notebook computer with Windows 7. I realize that the sound hardware that is built-in (Sigmatel) is probably junk compared to real interfaces, but the computer can play decent audio into headphones from WAV or MP3 files. It is for experimentation, not a production mix. The computer has a 2GHz dual core CPU and can play 1080p video with AC3 audio smoothly, so it is not underpowered.

I set up a really simple test scenario with the 2 track MIDI sequence "2-Part Invention #13 in A minor", and the DreamStation DXi2 soft synth.  I got continuous clicking/dropouts in the audio. I tried both WDM/KS and MME drivers, but they behave the same. I've tried various settings, but the only thing that has an effect is the buffer size slider under Mixing Latency. If I put the slider as high as it goes (349mS), the rate of dropouts slows down. If I move the slider lower, the dropouts are faster.

By sheer accident, I discovered that when I set the slider to exactly 31.9mS (1408 samples), it works! No dropouts or clicks. Move it the slightest amount either way, and there are continuous clicks and dropouts.

Can anybody explain this? Is it only attributed to bad drivers from Dell and/or Sigmatel? Or is there some other setting in Sonar that could be involved?

What did you enter your Midi data with? MME is ancient, don't even consider it. Windows 7 and MME? Who could explain that rate without being a computer scientist? I can't explain why 31.9 ms even showed up on the slider graph. That's horrible latency. How can you even use it? Get a real interface for music-audio. USB. You need to list what you are using for input-output. I'm sorry to be the one to tell you, but this art is much more complicated than plugging into the pink jack on your computer.
The whole chain of devices is involved. Settings in Sonar, settings on your "sound card", the list goes on.
Tel us what sample rates you're using, what controllers you're using, your computer can handle a lot but if you don't feed it the right information and sync it up right with devices-soundcards-controllers, you'll get nothing but greif.