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RE: Real-world disconnects



    I couldn't find any information about MWI disconnect in the PCI spec
(v2.2). However, in the PCI-to-PCI Bridge v1.1 spec, it did mention about it
on page 73 section 5.2.1.4. In short, if the MWI is not disconnected in the
boundary of the cacheline, the master should use the MW command for the rest
of the data.

James Lam. 

> ----------
> From: 	Patrick Maupin[SMTP:pmaupin@jump.net]
> Sent: 	Tuesday, October 31, 2000 9:56 AM
> To: 	pci-sig@znyx.com
> Subject: 	Re: Real-world disconnects
> 
> For MWI, the controller must transfer entire cachelines,
> according to the spec.  It is not allowed to stop on
> a partial transfer.
> 
> Assuming linear addressing (and your controller could
> refuse cachline wrap mode addressing if you only support
> linear mode), the disconnect must always occur on a
> cacheline boundary.
> 
> So, I cannot say what the percentage of broken controllers
> is, but it _ought_ to approach 0%.
> 
> Pat
> 
> 
> Marco Brambilla wrote:
> > 
> > Hello, world
> > 
> > I have a strange question ?
> > 
> > As we all know, a target (the host PC memory) can ideally disconnect any
> > transaction on any data phase it likes.
> > 
> > Does anyone know what is the likeliness (or percentage rate) of the
> > current chipsets disconnecting a MWI on non-cacheline boundaries ?
> > 
> > Let me explain better:
> > 
> > My system starts a MWI whose length is multiple of one cacheline
> > (actually 8 or 16 dw).
> > What is the likeliness of the memory controller disconnecting this kind
> > of transaction not on cacheline boundaries ?
> > 
> > Of course any application must work in any case, but this is just for
> > some sort of profiling.
> > 
> > Thanks, Marco.
> > 
> > --
> > -------------------------------------------------------
> >  Marco BRAMBILLA
> > 
> >  STMicroelectronics
> >  Via C. Olivetti, 2
> >  20041 Agrate Brianza (MI)
> >  ITALY
> > 
> >  TPA - Wireline Communications Division
> >  tel   : +39 039 603.5064   (ST Agrate - TINA 050 5064)
> >  tel   : +33 4 7658.5063    (ST Meylan - TINA 041 5063)
> >  fax   : +33 4 7658.5410    (ST Meylan - TINA 041 5410)
> >  mailto:marco-tpa.brambilla@st.com
> > -------------------------------------------------------
> 
> -- 
> Patrick Maupin
> 5216 Crooked Oak Cove
> Austin, Texas 78749
> 512 891 6037
>