Prev: About Interrupt Problem in RHEL-5
Next: Need help on getting the original source code of eZ430 Chronos
From: Walter Banks on 10 Jun 2010 16:45


Paul Keinanen wrote:

> On Thu, 10 Jun 2010 15:10:14 +0100, John Devereux
> <john(a)devereux.me.uk> wrote:
>
> >Perhaps there are special circumstances, like when lives or -- (gasp) --
> >actual *money* is at stake :)
>
> In such situations, double or triple redundant systems are typically
> used, which allows much more sanity cross checks than a simple
> watchdog.

Redundant sometimes, but redundancy has its drawbacks as well
look at the very first flight of the space shuttle. Triple redundancy
did not prevent a failure for the the processors to boot up and
communicate.

In automotive the starting transient that crashes one processor
probably would crash two or three.

There are alternatives for reliable systems, redundancy tends to
find common cause in a system. For processors error correcting
registers and memory help. Software consistency checks
help.

Regards,


Walter..
--
Walter Banks
Byte Craft Limited
http://www.bytecraft.com





From: Paul Keinanen on 11 Jun 2010 02:32
On Thu, 10 Jun 2010 16:45:26 -0400, Walter Banks
<walter(a)bytecraft.com> wrote:

>
>
>Paul Keinanen wrote:
>
>> On Thu, 10 Jun 2010 15:10:14 +0100, John Devereux
>> <john(a)devereux.me.uk> wrote:
>>
>> >Perhaps there are special circumstances, like when lives or -- (gasp) --
>> >actual *money* is at stake :)
>>
>> In such situations, double or triple redundant systems are typically
>> used, which allows much more sanity cross checks than a simple
>> watchdog.
>
>Redundant sometimes, but redundancy has its drawbacks as well
>look at the very first flight of the space shuttle. Triple redundancy
>did not prevent a failure for the the processors to boot up and
>communicate.

It worked perfectly, preventing the launch in a faulty vehicle.

>In automotive the starting transient that crashes one processor
>probably would crash two or three.

If this prevents operating such faulty vehicle, then fine.

First  |  Prev  | 
Pages: 1 2 3 4 5 6
Prev: About Interrupt Problem in RHEL-5
Next: Need help on getting the original source code of eZ430 Chronos