Noel Chiappa <jnc@mercury.lcs.mit.edu> writes:

> ISTR reading that it runs in Supervisor mode (no doubt so it could use the
> Supervisor mode virtual address space, and not have to go crazy with overlays
> in the Kernet space).

Indeed.  From "Installing and Operating 2.11BSD on the PDP-11":

    The networking in 2.11BSD runs in supervisor mode, separate from
    the mainstream kernel.  There is room without overlaying to hold
    both a SL/IP and ethernet driver.  This is a major win, as it
    allows the networking to maintain its mbufs in normal data
    space, among other things.

-tih
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