New motherboard refusing to go through POST. Take out modem (GVC Model F-115I/R2F Conexant RS56-PCI chipset based) and mobo and computer work perfectly. Put modem in, mobo doesn't POST. PS is known good. Given everything equal in the two scenarios, how (electrically speaking) can a PCI card prevent a mobo from going through POST. Is it something of a short circuit? Need to know because I don't want to diagnose bad mobos incorrectly.
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i dunno.if it were me i would try another known good pci card in that slot and i would try the modem in another slot and if that all failed i would blame mb
If you try the modem in a different slot and it still does not POST, you are at least 90% certain that the modem is bad.
A fried PCI modem is the number one cause of "dead" PCs after a thunderstorm.
If the controller IC on the modem fails such that it locks the data lines on the PCI bus, it can cause a halt state for the CPU and stop the POST process.
Once you verify that the modem is bad, physically destroy the PCI connector and properly dispose of the modem.
Thank you Chas. As a matter of fact it was after a thunderstorm. I did try the modem in a different slot as you said and it still did not POST. Thank you also for the explanation. I didn't realize data lines could get "locked" and cause a halt state for the CPU. I have seen a similar case with a bad disk drive/controller and I always wondered how the POST would stop. Not knowing this issue I had ordered a new motherboard (perhaps prematurely). Now I need to buy a new modem anyway. Oh well, I guess I should only charge the customer for the modem plus labor. Thank you so much!
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Motherboard or modem?