Thank you for your reply and the link.
I understand that the matter is a bit complicated and that there is no solution out of the box.
I succeeded in the past to install ubuntu on AC100 using essentially instructions present in
https://wiki.ubuntu.com/ARM/TEGRA/AC100.
One has to use the tool nvflash to copy a file called ubuntu-12.04-preinstalled-desktop-armhf+ac100.bootimg to AC100 and then in another step a file which I understand is the full "preassembled Ubuntu desktop". This second file is called ubuntu-12.04-preinstalled-desktop-armhf+ac100.tar.gz.
I understand that if a similar tgz file containing a "preassembled tiny core linux" is not available I will not be able to run TCL on AC100.
Regards,
Olivier
PS. links in
https://wiki.ubuntu.com/ARM/TEGRA/AC100. are now dead but I have copies of the relevant files on my old HDDs