AMD64 performance degrade under nforce310 computer

[Jacky Cao]

I am working on a AMD 64 4400+ with nforce310 chipset computer. It's
very fast under i386 FreeBSD 8.1 distro, but obviously slower in
amd64. I first notice this because I issue 'gmake -j200' without feel
a thing on i386 while it's quite lag under 'gmake -j4' on amd64. After
a little observation, it's seems disk accessing is slow, the nforce
disk driver is a key point, but I'm not sure about it.

Any suggestion? I thought 64bit x86 should be more faster than i386.