Yes, either internally MUXd for 4 devices or externally MUXd for 15 devices.
Thanks for the correction, I mean external not built-in.
I'd like to find a way to use the CS lead that actually isn't connected to any of the Arduino pins
Ummm, using telepathy?
Funny, but no. Come on man, give me more credit than that
As we've covered, the most convenient way of doing this managing the CS pin myself. Ok, done. I'm already there but using the SPI library configures by default to use CS pin connected to pin 52. I know there are four but as far as I can tell there are only 3 connected on the Due (4, 10, and 52.) All of which I'm using for other purposes (or was until this happened.) So I want to use the 4th CS pin with SPI precisely so that it is NOT being used and all of the others will be available for me to use with other things. As it is now, I've had to remove pin 52 from use...disappointing. Since I'm already using pin 10 to manage CS myself, I do not want my transfers using SPI library to mess with any of the other exposed pins on the Due so when I say I want to use it, I mean that I want it's use to be ignored since I can't seem to get away without using at least *something* based on the way the hardware and SPI library for the Due are implemented.
There should be no relationship between the two, I suspect a bug in either your code or the libraries.
My bet is on the libraries and no it isn't because I think my code is all Rosy just because it's my code. It's because I've spent enough time troubleshooting this and studying the data sheet that I have good supporting evidence.