Is COMPAT_43 really required on alpha?

[Dave Huang <khym%azeotrope.org@localhost>]

I was looking over my kernel config file and spotted:

# 4.3BSD compatibility.  Should be optional, but necessary for now.
options         COMPAT_43

That's been there forever--dating back to r1.1 of 
sys/arch/alpha/conf/GENERIC. Anyone know if it's *really* necessary? 
Neither the i386, amd64, nor mac68k GENERICs claim that it's necessary. 
Just curious :)