Onboard cache is part of the drive. The easiest way is to Google for the make-model spec sheet.
But almost any modern drive has some device cache
I differ in the opinion to USE write behind cache
WBC only makes it appear faster ...
BUT at a risk when there are multiple files to be written that must be done in lockstep.
(I come from a DOS database background where there could be as many as 42 files in a DB family that needed to be touched-up if there was a layout or structure change. Delay one file before the main refreshed and they were declare mismatched orphans (and discarded) )
The solution was to always take the slower, write cache OFF, approach.
It is your data (and modern drives ARE lots faster).