Another issue - offline mixdown vs. latency

Why is offline audio mixdown affected with soundcard latency? When using 64 samples (few msec latency), mixdown takes over 12 minutes, when switched to 512 samples, offline mixdown is ready in 3 minutes. Just simple project with NI Kontakt only with several MIDI and several instruments, nothing else. Downmixing just one channel - Kontakt output. When mixdowning, Cubase disables all GUI functions, no audio used, so why it races with soundcard??

System specs please or no-one has a clue.

sounds to me like your card doesn’t function well at lower sample rates. Probably throwing errors out the wazoo so has to retry a bazillion times.

PC Win 7 64bit quad core, over 3GHz, firewire Motu 828mk3, 64bit MOTU drivers. Sure not a problem with audio device (MOTU seems to work correctly all the time). Why is offline render affected by it? No audio card needed at this moment surely. Why must CPU race between rendering material and wasting time with pointless handling audio ports?

Sometimes the way you think something works is contrary to the way something actually works.

Sure, sometimes things do not go or go strange, but it’s not surprising that mostly with Cubase, howgh:-))

Nope. Only when YOU use Cubase. :mrgreen:
What you describe should not be happening. You probably need to go to support on this one both here and at MOTU.
My arguable observation is that your system is on the performance cusp for Cubase 6.5 and the extra data you’re throwing at the CPU and northbridge is getting bottlenecked somewhere.