with cpu_switch in C:
neelnatu4# uname -a
FreeBSD neelnatu4.hq.netapp.com 9.0-CURRENT FreeBSD 9.0-CURRENT #50 r203271M: Sat Jan 30 21:18:46 PST 2010     neelnatu@neelnatu1.hq.netapp.com:/usr/obj/mips/usr/freebsd/head/sys/SWARM  mips

neelnatu4# pwd
/usr/src

neelnatu4# mount
/dev/ad0 on / (ufs, local)
devfs on /dev (devfs, local)
10.33.24.125:/usr/nfsroot/pub/neelnatu4 on /mnt (nfs)

neelnatu4# setenv MAKEOBJDIRPREFIX /mnt

neelnatu4# /usr/bin/time make -j2 buildworld
--------------------------------------------------------------
>>> World build completed on Sun Jan 31 14:20:55 UTC 2010
--------------------------------------------------------------
    31963.24 real     23467.67 user      5573.34 sys

with cpu_switch in assembly:

neelnatu4# uname -a
FreeBSD neelnatu4.hq.netapp.com 9.0-CURRENT FreeBSD 9.0-CURRENT #49 r203179:203180M: Sat Jan 30 00:27:05 PST 2010     neelnatu@neelnatu1.hq.netapp.com:/usr/obj/mips/usr/freebsd/head/sys/SWARM  mips

neelnatu4# pwd
/usr/src

neelnatu4# mount
/dev/ad0 on / (ufs, local)
devfs on /dev (devfs, local)
neelnatu1.hq.netapp.com:/usr/nfsroot/pub/neelnatu4 on /mnt (nfs)

neelnatu4# setenv MAKEOBJDIRPREFIX /mnt

neelnatu4# /usr/bin/time make -j2 buildworld
--------------------------------------------------------------
>>> World build completed on Mon Feb  1 03:02:17 UTC 2010
--------------------------------------------------------------
    32058.48 real     23451.75 user      5595.32 sys