Re: NMI trap and 2.1.37-7

Linus Torvalds (
14 May 1997 06:20:27 GMT

In article <>,
Riccardo Facchetti <> wrote:
>There is just one point, this for the developers.
>Now the kernel have the io_check_error toggling the I/O CHCK bit, this
>clears the I/O CHCK flag. I can't see any reason for not to toggle memory
>errors bit too. Anyway these flags are not used so why toggling one and
>not the other ?

That's because "io_check_error()" wasn't actually developed due to the
noises on the mailing lists, but for my own perfsonal SMP reasons.

I've got a card that generates an NMI through the ISA IOCHK line
(_extremely_ simple to build: get a ISA prototype board, and connect A1
and B1 with a button ;). So if I have a dead machine, I can press a
button and get a register dump.

As such I wasn't really interested in the memory parity NMI at all,
especially as that NMI is useless anyway (you can't get any information
on what part of memory is bad).

If people are really intersted in memory parity checking, they should
look into the Machine Check Architecture supported in newer CPU's and
use ECC RAM. The Machine Check Architecture (MCA - I just bet intel did
that just to mess with the minds of people who have a MCA bus) is a lot
more useful when it comes to memory parity errors than the NMI line ever