On Thu, May 22, 2008 at 1:43 AM, Mayank Kaushik <mayank.utexas@xxxxxxxxx> wrote: > Hi everyone, > > I have been reading Chapter 9 of the Intel Processor Manuals, Vol 3A > (System Programming Guide), which details the APIC. > I have noticed that we often have to add the noapic and nolapic > arguments to the kernel command line to make devices like the wireless > card work. The explanation for these options simply stated that this > is to overcome "buggy bios implementations". > > Can someone here explain what could possibly be the bug in the bios > that necessitates the use of these arguments? Further, what does the > kernel do differently when it sees these arguments? > > Thanks for your help, > Mayank > > -- For an example of CPU bugs, check the revision guide for AMD processor: http://www.datasheetcatalog.org/datasheet/AdvancedMicroDevices/mXuuwq.pdf And from page 11 to the end are all the different Erratum nos: and specifically for erratum #22: inside kernel source code drivers/pci/quirks.c: /* * The AMD io apic can hang the box when an apic irq is masked. * We check all revs >= B0 (yet not in the pre production!) as the bug * is currently marked NoFix * * We have multiple reports of hangs with this chipset that went away with * noapic specified. For the moment we assume it's the erratum. We may be wrong * of course. However the advice is demonstrably good even if so.. */ static void __devinit quirk_amd_ioapic(struct pci_dev *dev) { if (dev->revision >= 0x02) { dev_warn(&dev->dev, "I/O APIC: AMD Erratum #22 may be present. In the event of instability try\n"); dev_warn(&dev->dev, " : booting with the \"noapic\" option\n"); } } DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_VIPER_7410, quirk_amd_ioapic); The above is the rectification for the error, basically by setting noapic option u overcome the error. Just an example. -- Regards, Peter Teoh -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
