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Re: PCI Address Decode querry!!!




Hi,
I expect all PCI-bridges will do smart things not to generate dual address
cycle when ad[63:32] == 0.

The following code would save address decode time without loss of any
generality:

During address cycle, generate match signal for 32-bit address BAR:
March = ad[31:12] == Bar[31:12];

If a dual address cycle is generated first, never generate match signal for
32-bit address BAR.

I would like to hear other's opinions.

Weng Tianxiang
Micro Memory Inc., CA 91311, US.


----- Original Message -----
From: Monish Shah <monishs_in@yahoo.com>
To: Narayan Kulshrestha <narayan@cmoschips.com>; <pci-sig@znyx.com>
Sent: Sunday, July 09, 2000 9:18 PM
Subject: Re: PCI Address Decode querry!!!


>
> > Hello !!
> >
> >
> > When PCI Bus 64 bit Bus is it mendatory for all the BARS to be 64 bit??
>
> No.
>
> > Or is it like this, for a 32 bit BAR match??
> >
> > match_occured = (ad[63:32] == 0 ) && (mask[31:12] & ad[31:12] ==
> > Bar[31:12])
>
> Yes, except that if AD[63:32]==0, you won't get a DAC (dual address
cycle).
>
> > Please give some real Idea on it!!
> >
> > Best rgds
> > Narayan
>
> Monish Shah
> Ascent Software
>
>