关于Pentium D的疑问

最近会帮朋友在一台Pentium D的主机上安装Gentoo，由于之前没接触过这种CPU，于是去看了下gentoo-wiki，上面这样说：

Pentium D 8xx / 9xx
vendor_id : GenuineIntel
cpu family : 15
model : 4
model name : Intel(R) Pentium(R) D CPU x.xxGHz
cpu cores : 2

Note: Because of the EM64T support, the Gentoo architecture for this chip is amd64. Warning: With this processor mysql 5 is completely broken using -march=amd64. Make sure you use -march=nocona. TODO: Could somebody please check the 9xx cpuinfo is identical to the 8xx cpuinfo?
Append: my 9xx registers model 6 not model 4. It also has syscall instead of pbe. It has constant_tsc and lahf_lm. It's missing est.

Note: For those who don't need the Intel's 64-bit extension(EM64T), just use the Pentium4(Prescott) flags with MAKEOPTS="-j3" which is on desktop in most of the cases the better choice *and* use CHOST="i686-pc-linux-gnu" (for a strictly 32-bit environment).

CHOST="x86_64-pc-linux-gnu"
CFLAGS="-march=nocona -O2 -pipe"
CXXFLAGS="${CFLAGS}"
MAKEOPTS="-j3"

看了之后有点迷糊，不知道有使用这款CPU经验的Gentoo users有什么建议？一直使用CHOST="x86_64-pc-linux-gnu"和-march=nocona会不会碰到什么问题？

想使用Intel 64-bit扩展的话用：
CHOST="x86_64-pc-linux-gnu"
CFLAGS="-march=nocona -O2 -pipe"
CXXFLAGS="${CFLAGS}"
MAKEOPTS="-j3"
-----------------------------------------------------------------------------------------------------
想使用32-bit的话用：
CHOST="i686-pc-linux-gnu"
CFLAGS="-march=prescott -O2 -pipe"
CXXFLAGS="${CFLAGS}"
MAKEOPTS="-j3"