I think, even if it IS possible to run an operating system like linux on an 8051 or alike, than you have to add so much extra hardware that it is not worth the effort.
8051's are developed for 'embedded' environments. That's what they are excellent for. Like, in most cases it is 'overdone' to mount a Pentium III or 4 in an embedded environment, it is the other way around not recommendable to use a microCONTROLLER for a linux environment. Think about it, standard 8051 is an 8 bit processor, while Linux is for 32 bit processors.....

Henk