SOYO SY-P4I845PEISA - Manual (Page 23)

Hardware Installation SY-P4I845PEISA/GEISA
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Note2: When you use an AGP add-in card on the P4I845GEISA
mainboard, the onboard VGA will automatically be disabled. It’s
not possible to use onboard VGA and an AGP add-in card at he
same time. For both versions (P4I845PEISA and P4I845GEISA)
note that when using a PCI VGA card, make sure that the “Init
Display setting” is set to PCI slot instead of onboard/AGP. Also,
note that when using a PCI VGA card the on chip VGA setup
option can be used to disable onboard VGA.