> On Mon, 10 May 1999, Stephen C. Tweedie wrote:
>
> > Hi,
> >
> > On Thu, 6 May 1999 10:54:21 -0700 (PDT), Dan Hollis
> > <goemon@sasami.anime.net> said:
> >
> > >> at least on cold power-on you first have to write something to RAM
> > >> to initialize the parity bit(s). if you try to read RAM first,
> > >> odds are 50% that the parity bit is wrong and you'll get an NMI...
>
> You don't really have to clear memory, i.e., write to it. All you
> have to do is read all of it with NMI disabled.
>
> Write 0x80 to port 0x70 to disable NMI, enable later by writing 0
> out the same port (it's the index register for the CMOS clock-chip).
> Since a read or write takes about the same time, it is usual to
> just write all memory to zeros, but it is not necessary.
why should reading memory update/set parity or ECC data ?
updating parity/ecc information can't happen for sure for every read because of
performance reasons. are there special bus/memory cycles if ecc/parity fails ?
I don't believe (at least for 8088/186/... this did _not_ happen).
>
> >
> > > Are you 100% sure about this? And what about warmboots.
> >
> > It is necessary to initialise ECC memory, yes, but the BIOS should do it
> > for you. I've only got one ECC box, but at least on that one the BIOS
> > definitely spends a while setting up the memory at boot time.
> >
>
>
> Cheers,
> Dick Johnson
> ***** FILE SYSTEM WAS MODIFIED *****
> Penguin : Linux version 2.2.6 on an i686 machine (400.59 BogoMips).
> Warning : It's hard to remain at the trailing edge of technology.
>
Harald
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