Well, I have to confirm what Atti said, I have the same board:
P450
It was in a HP machine.
Socket mpga478B
north bridge undetermined
south bridge Intel FW82801EB...SL73Z
Bios SMSC Phoenix 1996 mk421
there is a broadcom chipset, and a little Delta box just below the connectors
onboard LAN, 4USB, //, serial, 2 PS2, video and sound
1.5V AGP slot
3 PCI 32 slot
and a weird darkish grey connector below the PCIs, looking a bit like a SCSI only twice wider, mentionning EXT PCI SLOT (also scsi pins with no jumper on near the battery...)
4 DDR1 slots (2 black, 2blue)
2 IDE (1 blue, 1 white)
1 floppy
2 SATA
clear cmos is a bright yellow button between the SATA connectors
SST chipset below
made in China
codebar sticker: PN#323091-001 P6B580MSVPK8AC AS#305374-001
REV 0M
another sticker near the processor : 374 REV0M S29
I haven't been able to start the board yet (there is a hood sense 3pin connector with no jumper on + a hood lock 5pin connector + a 19pin connector marked Security...)
I would really appreciate a manuel for that board!!!
(and if I get there, I'll probably need drivers as well...)