Windows 95 Does Not Start on Dell Omniplex

• Microsoft Windows 95

SYMPTOMS

After you install a PCI card in one of the PCI expansion slots of the Dell Omniplex computer, Windows 95 does not start.

CAUSE

The Dell Omniplex has two PCI slots and four interrupts available for PCI cards: 9, 10, 11, and 15. The Dell Omniplex ships with three interrupt- claiming PCI devices installed: a video card on the motherboard that claims IRQ 9, an NCR 810 SCSI card on the motherboard that controls the hard drive and the CD ROM, and an external NCR SCSI. Each of these devices uses a different interrupt, leaving one PCI IRQ line available for the remaining PCI slot.

If you use the remaining interrupt by installing an ISA card (for example, an ISA network card or sound card), and then try to plug a PCI network card into the remaining slot, the PCI network card is forced to share an interrupt.

According to the specification for this bus architecture, PCI devices can share interrupts. However, the NCR SCSI controller does not share interrupts correctly. If the controller for the hard drive is forced to share an interrupt, the computer stops responding (hangs) when the controller tries to access the disk when Windows 95 starts.

RESOLUTION

Remove the PCI card that you added and adjust the resources of your non-PCI cards so that none of them are using interrupts 9, 10, 11, or 15. Then reinstall the PCI card so that Windows 95 can redetect it.

The Dell Omniplex computer is manufactured by Dell Computer Corporation, a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.