64bit Audio engine vs double precision engine and a dithering question (Noel? please :) )

Hi guys,
 
Guess these are some advanced questions so would really appreciate your help.
 
1) Is there a difference between the 64 Bit Double precision Cakewalk optionally has (essentially the mixer operating at 64 bit floating point wordlength ) and the 64 bit audio engine advertised with Sonar? I saw an explanation a while ago in this Youtube video about the new Cubase 64 bit audio engine where the narrator claimed that this has nothing to do with wordlength but with rounding and avoiding quantisation errors. Or are they one and the same and the narrator is wrong?
 
2) Does Cakewalk dither at the Master fader output automatically? At some point all our floating point audio reaches the driver of our interface, which in most cases will operate at fixed 24 bit wordlength. Does Cakewalk automatically dither in this case in order to not truncate what we hear at the real time output? 

Hi Noel,
 
Thanks for this! So are 64bit floating point (which is the word length of the file) and 64 bit summing/math the same?
Or is the 64 bit math/summing on by default and all the 64 bit tick box does is activating the floating point option, giving us more (theoretical) headroom. Or are they the same and I'm making this more complicated than it is.
 
Essentially are mixing engine and double precision 64 bit floating point files the same thing or are they separate? 

Mannymac
Hi Noel,
 
Thanks for this! So are 64bit floating point (which is the word length of the file) and 64 bit summing/math the same?
Or is the 64 bit math/summing on by default and all the 64 bit tick box does is activating the floating point option, giving us more (theoretical) headroom. Or are they the same and I'm making this more complicated than it is.
 
Essentially are mixing engine and double precision 64 bit floating point files the same thing or are they separate? 

No if the 64 bit mix engine is off in the audio settings then all mixing is done in 32 bit floating point irrespective of the audio word length in the track data. The mix engine setting is controlling how mixing is done and all audio data is up/down converted to the mix engine bit depth prior to mixing.