I've got Redhat 8.0 running on a Compaq Proliant ML370 G3. The base
install left me with a 2.4.18 kernel and a grub.conf that looked like:
boot=/dev/cciss/c0d0
default=2
timeout=10
splashimage=(hd0,0)/grub/splash.xpm.gz
title Red Hat Linux (2.4.18-14smp)
root (hd0,0)
kernel /vmlinuz-2.4.18-14smp ro root=LABEL=/
initrd /initrd-2.4.18-14smp.img
title Red Hat Linux-up (2.4.18-14)
root (hd0,0)
kernel /vmlinuz-2.4.18-14 ro root=LABEL=/
initrd /initrd-2.4.18-14.img

I built a new kernel, using 2.4.23, and did the usual setup. I added it
to grub.conf using the same format as the two initial entries:
title Red Hat Linux (2.4.23)
root (hd0,0)
kernel /vmlinuz-2.4.23 ro root=LABEL=/
initrd /initrd-2.4.23.img
but when I tried to boot from it I got a message complaining about an
invalid "root=" argument. After a great deal of screwing around I
finally arrived at:
title Linux USB (2.4.23)
root (hd0,0)
kernel /vmlinuz-2.4.23 ro root=/dev/cciss/c0d0p3
initrd /initrd-2.4.23.img
which works.

So my question is, how come the difference in "root=" arguments? Both
2.4.18 and 2.4.23 are booting off the Compaq Smart Array controller, and
both are using the same partitions, etc. I'm at a loss here. I've
checked several web sites with info on grub configuration, but have not
seen anything that helps me understand this.