I'd go for uCLinux . It's been ported for ARM, it has strong user base and a decent portfolio of evaluation boars exists. There are couple of other Linux/ARM projects around and you'll see.
I'd here the port for uCLinux for '51s but google did not show???????
plz where is it????????
You were told to forget about Linux combined with C51. Still, you insist on diving in the boiling abyss...