I have been trying to test the upsampling in the newest update and it does not seem to work.
 
Background: I have previously tested and verified that if I import the midi from a truepianos track into a new file and bounce it using 96khz it sounds far superior to the same bounce done at both 48khz and at 44.1khz even after importing back into the source project and the sample rate is converted.
 
I tried to test this in Foxboro and so far i'm disappointed.
 
First I loaded a project with Truepianos in it and just did a bounce to track using the synth output as the source.  this is the control in the test.
 
Then I enabled the option to upsample and performed the same process bounce to track and compared the 2 tracks. There is no difference between the 2 and there sound be. as I pointed out that I verified previously that upsampling to 96khz made a noticable difference when performed in a new project set to the higher sample rate.
 
The Foxboro pdf hints that the upsample rate is set someplace but I have not been able to determine where this is. Perhaps that is the missing piece.
 
Here is a quote from the pdf:
 
When selected, SONAR begins the bounce process by upsampling the incoming audio to the specified higher sample rate, processes the plug-in at the new rate, then downsamples the resulting output to the current project sample rate.
 
Any ideas?

I've just run a very quick test with a Dim Pro Rhodes sound and with 'Upsample On Render' checked there was a noticeable difference in the sound after I froze the track. I'm not sure of the higher sample rate setting either, but I can report there was a 'cleaner' sound afterwards. I guess this indicates it is working here. 

Here you go, found this:
 
Upsampling settings
The per plug-in upsample settings are stored in the Audi.ini file, under the key [PluginUpsampler] like this:
[PluginUpsampler]
{141AC902-4357-626C-424F-4F5354317E31}.EnableFlags=1
{141AC902-4357-626C-424F-4F5354317E31}.SampleRate=96000
A plug-in is only listed in the Audi.ini file after you have toggled its Upsample on Render option. The long number string is the plug-in’s CLSID, and is unique for each plug-in.
The {Plug-in CLSID}.EnableFlags= variable specifies whether resampling is applied. It corresponds to the Upsample on Render setting in SONAR’s UI. A value of 1 enables resampling at render time. A value of 0 (zero) disables resampling.
The {Plug-in CLSID}.SampleRate= variable specifies the per plug-in upsampling rate. It defaults to a value of 0 (zero), which means “resample at twice the project sample rate”. The max sample rate is 384000 Hz. This variable is not stored in the Audi.ini file by default, so it must be manually added if want to change a plug-in’s upsample rate (Tip: copy the CLSID from the corresponding EnableFlags= variable).
 
So not changing any settings doubles the project sample rate. HTH

Interesting I see an enable flag in the aud.ini file but no sample rate is specified.
 
I'm on the 64 bit version are you?
 
 
edit ok I see now that it has to be manually specified. Where did you find the additional information?

ok I did some more testing and I guess I just needed to clean out my ears.
 
LOL
 
This is great I wonder if there is a list of plugins that would benefit from this anywhere?