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Sometimes when developing Windows NT/2000/XP/2003 device drivers the system completely freezes to the point where only a hardware reset will resolve the problem. Unfortunately the system state is completely lost after a hardware reset which makes it not possible to debug the cause of the system freeze. By using this PCI Dump Switch Card a Windows crash dump file can be saved to disk even if the system is completely locked up. The PCI Dump Switch Card is a PCI card that induces an NMI interrupt when the button on the back of the card is pressed. Windows NT 4.0 SP4 and newer platforms (2000, XP, 2003) will create a crash dump file if special registry settings are enabled. This will allow the state of a frozen system to be saved into the crash dump and later analyzed in WinDbg (or other kernel debuggers that understand the NT crash dump file format). Other operating systems may have similar functionality since the PCI bus is platform independent but the Dump Switch Card has only been tested on Windows platforms. The PCI Crash Dump Card asserts the SERR signal on the PCI bus for one PCI clock cycle when the button is pressed. The SERR signal is then tri-stated. The SERR signal on the PCI bus is normally routed to the NMI input on the CPU via the chipset used. All PCI devices can assert the SERR signal whenever a serious system error has occurred. On most motherboards the SERR signal is used to detect memory parity errors. Because of this a 'parity error' message may be displayed by Windows NT when the button is pressed on the Dump Switch Card (the exact message is dependant on the system hardware or rather by the HAL used for the target hardware). The SERR signal is a wire-or signal that is common for all PCI devices. The PCI bus has a pull-up resistor on the SERR signal so the PCI devices should only pull SERR down when a device wants to assert SERR, they never drive SERR. The output transistor stage on the PCI Dump Switch Card implements an open collector output which pulls down SERR when the output from the PLD is asserted. Note that in rare cases, some PC's do not map the SERR signal to the NMI of the CPU. On these platforms it is not possible to create a Crash Dump using a dump switch cards like the one described here. A full technical description of this Dump Switch Card is available here: http:// /DumpSwitchCard.htm (please look at our rules and privacy policy) |
kara-morton@machine--tools.com (Kara Morton) for additional information. This email is used for forwarding to newsgroup user.
