FreeBSD 6 - Do i need both CD1 and CD2 ?

[JK]

On Tue, 3 Jan 2006 05:18:59 -0800 (PST)
  Adam Nealis <adamnealis at yahoo.co.uk> wrote:
> --- "FlashWebHost.com" <flashweb at gmail.com> wrote:
> 
>> Hi,
>> 
>> I am using FreeBSD 5.2 on my local computer.
>> 
>> I want to upgrade to FreeBSD 6.0
>> 
>> Do i need to download both files ?
> 
> No. CD1 will give you as much as the OS plus X11 plus all sources. 
>Plus
> the complete ports tree as of 6.0-RELEASE.
> 
> CD2 contains several hundred binary packages, but are not required 
>for the
> OS upgrade.

I've always wondered this.  I'm running 5.1.  Can I upgrade to 6.x in 
place, i.e. without having to full install and wipe my filesystem etc?

If so, how do I do that?  I couldn't find anything in the Handbook or 
anywhere that says one can do this.