install 6.4 on Dell OPTIPLEX 755 panics

[Jin Guojun]

Install 6.4 from DVD on DELL Optiplex 755 (Core 2 DUE E6550 CPU with 2GB 
memory) always panic at
last stage of boot.
Is this a hardware specific (this machine only) issue? or is it a known 
hardware problem for DELL Optiplex 755?

Disable ACPI does not help. Also noticed that 6.4 did not detect second 
core on this machine.

-Jin

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md0: Preload image </boot/mfsboot> 4423680 bytes at 0xc0bc79dc
ad8: 238418MB <Seagate ST3250820AS 3.ADG> at ata4-master SATA300
acd0: DVDROM <TSSTcorpDVD-ROM TS-H353B/D200> at ata5-master SATA150
acd1: DVDR <PBDS DVD+/-RW DH-16W1S/2D14> at ata6-master SATA150
umass0: at uhub6 port 2 (addr 2) disconected


Fatal trap 12: page fault while in kernel mode
fault virtual address    = 0x20
fault code               = supervisor read, page not present
instruction pointer      = 0x20:0xc045d1f6
stack pointer            = 0x28:0xe56c8c64
frame pointer            = 0x28:0xe56c8c68
code segment             = base 0x0, limit 0dffff, type 0x1b
                         = DPL 0, pres 1, def32 1, gran 1
processor eflags         = interrupt enabled, resume, IOPL = 1
current process          = 11 (swi4: clock sio)
trap number              = 12
panic: page fault