FreeBSD 8-current/amd64 very slowly loader(8) issue

I have moved my main work pc from i386 FreeBSD to amd64
to get more memory use and ZFS checking.

I'm wondering why loader loads kernel and kernel modules
very slowly.

   [M/B and CPU info]
   # dmidecode
   (snip)
   Base Board Information
          Manufacturer: Gigabyte Technology Co., Ltd.
           Product Name: EP45-UD3LR
           Version: x.x
           Serial Number:
   (snip)
           Version: Intel(R) Core(TM)2 Quad CPU
           Voltage: 1.0 V
           External Clock: 333 MHz
           Max Speed: 4000 MHz
           Current Speed: 2500 MHz
           Status: Populated, Enabled
           Upgrade: Socket 478
   (snip)
           Maximum Memory Module Size: 1024 MB
           Maximum Total Memory Size: 4096 MB
   (snip)
   #

FreeBSD amd64 on the other work pc (E6600, DP965LT, 2GB mem),
loader works incredible slow, but after I changed BIOS CMOS
config turning AHCI off, it works very well.

So I am doubting AHCI works well, but turing off AHCI feature of
EP45-UD3LR M/B, amd64 loader still remains in very slow working.

Anyone has any ideas?
Thanks

-- 
   Daichi GOTO, http://people.freebsd.org/~daichi