In a long past architecture the "OS" was in hardware based literal ROM.
And a further question came up that shows my ignorance of real applied usages. The full experiment is in direct result of my NOT knowing in advance how to make this work.And wanting to have it for daily use if it does. Since it has become trivial to run Ramdisk Distros I am planning on an experiment. Recently I noticed several USB cards have one or more ports facing towards the INSIDE of the case. The logical to me use will be loading some bootable from USB drive version onto a properly sized flash drive. So far it looks like a "so what" trivial re-inventing trip. This is more my asking for direction in both WHICH distro is suited to do this with and some help in directions for making it do what is needed for this. The devil for me is in the details of altering that installed distro so it can use a drive not part of the same one it lives on. YES this appears to be a tangent or even restatement of the post RE: OS and Data isolation. This is a case detached from that for a different reason. Flash memories of some cheaper design have limited write cycles. Having the OS on a flash drive that only gets written to when the OS itself is changed as in moving from a 5.x up to 7.06 type change. So the flash will not be "worn out"