Originally posted by Simen1 The bottleneck is USB2. There is constrains within the USB2 standard that wont allow use of the full theoretical bandwith. Its practically limited to around 35 MB/s. Read more about the limit
here.
I believe K-1 potentially could transfer much faster then that if it had USB3 hardware. The bottleneck is most likely the USB2 interface, not something else.
You're probably right about the real world performance.
But I think K-3 owners don't really get beyond 35MB/s either, and they have USB3.
The K-1 and D810 both shoot at about 5fps, so the Fujitsu bus can write to RAM okay. Once the buffer fills, though, it's then that slow write to the card.
MSC mode reads about 36MB/s from the K-3, PTP about 19MB/s, so there is a bottleneck there, Simen1.
Taking the card out of the camera and transferring images with a USB3 card reader gets about 90MB/s.
Northrup should know better because he's technically minded (I used to have a couple of his system administration books as references) but like the lenses comparison, he obviously hasn't researched the issue.