What is the default quantum time for Mac OS X?(e.g. in seconds, ms)
and
What kind of task scheduler Mac OS X uses?(e.g. Round Robin, Priority)
If I knew what you were talking about, I bet I'd say those are two darned good question.
The underlying subsystem is pretty much BSD (freeBSD i think) so you might be able to find the answers there.
Sorry for the lame response.
Yeah... that also confuses me 
Sorry.
Also OS X is based on NeXTSTEP (An OS that Steven Jobs used during his computers when he left Apple) and, yes, freeBSD. This site ( macOS Ventura - Apple ) is about OS X 10.3, which is an OS X version. I hope this helps.
I couldn't find an exact answer.. perhaps this will help?
About Multitasking on the Mac OS
There's a section on task scheduling but I didn't see answers to your questions. Just out of curiosity, why do you need to know the answers to these questions anyway?
Going down the FreeBSD path gets this dealie:
On page six of this document
Hope that helps somewhat in your quest for the default quantum value.
For the scheduler question you can probably get the information from the same document. 
It was written somewhere in 1999, so the data should be relatively accurate. 
Yo!! Thank you guys a lot~~
Now i have more information.. cos I'm doing an OS overview of MAC OS X, and i need to show some examples on how the OS multitasks between different jobs, including the details like average waiting time, turnaround time.