Boot / Install freeze with Dell PE1850 5.3 and amd64

[Claus Guttesen]

> The troubling machine is a Dell 1850 with 2x2.8GHZ
> Noncona, 4GB of RAM
> The working machine is a Dell 1850 with 2.2.8GHZ
> Noncona, 1GB of RAM, 
> which installs fine with amd64.
> 
> It hangs initializing the ATA CD-ROMs:

Had the same problem with a Dell 2850 and 4 GB RAM.
Found the following hints on freebsd.org:

1. Press 6 to enter boot prompt.
2. Type 'set hw.physmem="2G"
3. Enter boot to boot :D
4. Cvsup to latest 5.3-stable by adding
*default release=cvs tag=RELENG_5
to your sup-file
5. Rebuild world and kernel as normal.
6. Reboot.

This made my Dell 2850 work without hw.physmem. If you
need to reboot before you have installed new
world/kernel don't forget to enter ph.physmem again.

Important that the cvs tag is *not* RELENG_5_3.

HTH
Claus