🚀 go-pugleaf

Craig Dewick wrote:
> 
> In <33797DC9.5A54@mailhost.km-mhm.comp.philips.com> "J.P.M. Theuws" <theuwsj@mailhost.km-mhm.comp.philips.com> writes:
> 
> >Does anyone know the exact differance between a "passive" and a "active"
> >terminator ?
> 
> A traditional SCSI terminator has a series of resistor dividers made from
> 220 and 330 ohm resistive elements.  For a single signal line, the circuit
> is like this:
> 
> +5v -------+--------
>            *
>            *
> data ------+---------
>            *
>            *
> gnd -------+---------
> 
> Each vertical pair of asterisks represents a single passive resistor. I
> can't remember if the 220 ohm or the 330 ohm sits between +5v and the
> signal line though. 8-)
> 
> Lots of these in a single assembly form a normal 'passive' terminator.
> It's easy to see why it's termed a passiver terminator because the voltage
> divider never changes it's parameters regardless of the electrical
> conditions of the SCSI cable. For longer cables especially, passive
> termination can often cause more problems than it solves.
> 
> An 'active' terminator is basically an automatically adjusting version of
> the passive terminator, and goes a long way to compensating for signal
> degradation in longer cables and in cable assemblies that stretch the
> electrical specs close to the limits described in the SCSI 'standards'.
> 
> >And does SUN always make use of a "active" terminator on the SCSI-bus...
> 
> Older machines like the Sun-3's and early Sparc-based models all used
> passive terminators, but I'm not sure about current and recent generation
> machines which have SCSI controllers integrated into big ASIC's with other
> major hardware 'components'. I suspect active termination is almost the
> norm now, especially with SCSI-2 and later interfaces.
> 
> Regards,
> 
> Craig.
> 
> --
>           Sun Ripened Kernels - http://www.zeta.org.au/~craig/srk.html
>                 Surplus and pre-loved Sun Microsystems equipment.
>                      Based in Sydney, Australia. Operated by
>         Craig Dewick - craig@zeta.org.au - http://www.zeta.org.au/~craig

Thanks Craig for the expanation.
Hans Theuws