[Cialug] Masters and Slaves

[Zachary Kotlarek]

On Nov 1, 2008, at 8:26 PM, Colin Burnett wrote:

> It's still P2P.  The host talks to the multiplier which then knows
> which port to talk to.  Between the host and multiplier is a
> bidirectional channel with only the host and the multiplier.  Between
> the multiplier and devices is a bidirectional channel with only the
> multiplier and the device.  It is *not* a shared bus.
>
> I presume we're arguing at different layers?

You're right of course: "shared bus" is the wrong terminology, as  
there is no direct signal connection among 3 or more nodes. So we are  
talking at different layers -- you're thinking signals and I'm  
thinking data.

I was reacting to the "no arbitration/addresses" part of your note --  
there's still a single physical link that uses addresses to  
distinguish between multiple endpoints, and there's still the  
potential for multiple endpoints to generate more data than the single  
uplink can transmit, which demands arbitration. Those two functions  
may not happen as part of the fundamental signaling protocol -- they  
may be encapsulated as data across an unarbitrated, addressless link  
that only the HBA and port multiplier see -- but they're still part of  
the overall SATA system.

	Zach

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