On Tue, 10 Apr 2001, Greg Lehey wrote:

> On Monday,  9 April 2001 at  8:31:40 -0400, Jon Lindgren wrote:
> > Stratus machines did have CPU failover, however, I don't think it
> > was to that extent.  IIRC they had 4 processors for each logical,
> > and the 4 would constantly check results with each other (via
> > hardware... not software...).  When one goes out of service due to
> > differences, the other 3 continue on as if nothing happened.  Kind
> > of neat; memory was the same way IIRC.  Unfortunately, VOS (its os)
> > never realy caught on (too much typing ;-) and FTX (later moved over
> > to HP-UX) had it's own set of problems...
> 
> IIRC Stratus had 4 processors per CPU, organized as two pairs which
> kept checks on each other.  If they disagreed, they both died and let
> the other pair get on with it.

Could be - it's been a long time since I've talked to the Stratus tech
guys, but I thought it was a "free-for-all" amoung the processors.  A 2x2
approach does seem a bit more pratical, tho (both logically and
schematic-wise), so you're probably correct.
 
[snip]

-
Jon
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