Re: [PATCH] NMI trap revised (was Re: NMI errors in 2.0.30??)

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Thu, 8 May 1997 09:27:45 +0200 (MET DST)


Riccardo Facchetti wrote:
>
> Is this a good idea ?
>
> On 6 May 1997, Matthias Urlichs wrote:
> >
> > The best memory checker is a kernel recompile, a network download, and a
> > floppy read. At the same time. Repeatedly. I have yet to see a problem that
> > didn't eventually show up under this kind of stress.

> +
> + /*
> + * May be sort out what memory chip is failing ?
> + * Heh ... with parity memory we can be a good memory
> + * test program too :)
> + * It should be something like:
> + *
> + * (1) disable NMI interrupts writing 1 in bit 7 of
> + * port 0x70
> + * (2) reset the NMI memory parity error flag (bit 7)
> + * toggling bit 2 of 0x61 port to 1 and then to 0
> + * (3) while all flat memory is tested:
> + * (4) write 4Kb page in memory
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> + * (5) test if any NMI is pending: if yes, the
> + * last page written is bogus, printk its
> + * address.
> + * (6) ++ page

I maintain the "sig11" page which explains a lot about bad memory. I
allows me to get lots of mails from people with different memory
problems. In more than 90% of the cases the problems only show when
you do a kernel compile. My memory test program (which is based on the
knowledge of a leading expert on semiconductor memory testing.) detects
only a very small percentage of memory trouble.

Roger.