Is this using the built-in speakers or the headphone jack?  Plug in an optical cable and see if the CPU doesn&#39;t drop a lot.  Or try a USB or Firewire interface.  <br><br>By default CoreAudio does a lot of processing on audio when using the built-in outputs.  It used to mainly be limiting to keep the shitty speakers from blowing, but it has expanded over time.  There is obviously a way to tell CoreAudio to cut that out, but how that is done via PortAudio is a question for the PA developers. <br>
<br>The ml_set_interrupts_enabled is the blocking.<br><br><div class="gmail_quote">On Tue, Nov 9, 2010 at 10:48 AM, Jamie Bullock <span dir="ltr">&lt;<a href="mailto:jamie@postlude.co.uk">jamie@postlude.co.uk</a>&gt;</span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div class="im"><br>
<br>
<br>
</div>pd doing &#39;nothing&#39;:<br>
<br>
        10.6%   10.6%   mach_kernel     ml_set_interrupts_enabled<br>
        9.4%    9.4%    DspFuncLib      iZRedist::DSP::Denoise::processWithLookahead(int, float* const*, int)<br>
        6.7%    6.7%    DspFuncLib      iZRedist::DSP::FftImpl::FftComplex_InPlace(iZRedist::DSP::Cmplx*) const<br>
        6.3%    6.3%    DspFuncLib      DspFuncHelper::process_IIR_xmm_LR(float*, float*, float*, float*, unsigned int)<br>
        3.8%    3.8%    DspFuncLib      iZRedist::Util::Log(float)<br>
        2.8%    2.8%    AppleHDA        NativeInt32ToFloat32_X86<br>
        2.5%    2.5%    DspFuncLib      iZRedist::DSP::FftImpl::FftReal(float const*, iZRedist::DSP::Cmplx*) const<br>
        2.3%    2.3%    DspFuncLib      DspFuncDRC::_dynamicRangeControl(float*, float*, unsigned long, unsigned long)<br>
        2.0%    2.0%    mach_kernel     lo_mach_scall<br>
<br></blockquote></div>