RE: Device at address 0

[Neal Palmer <neal@dinigroup.com>]

David,

  it goes beyond that.  There was a generation of BIOS versions that would 
disable a device by setting it's address to 0.  And if your device didn't 
recognize that and disable the BAR, then the system would usually stop 
immediately.
  There may still be BIOS versions in production that still do it today...

-- Neal

On Thu, 1 Aug 2002, O'Shea, David J wrote:

> 
> The Specification doesn't prevent a base address of 0.
> The enable disable is really in the command register for
> decode of I/O or memory.
> 
> However, many implementations improperly make the assumption
> that 0 in the basereg also means disabled.  In practice, the
> mistake doesn't usually amount to much, since most Intel or
> even most "non-Intel" systems generally have memory located
> at address 0, and usually preclude I/O or memory assignments
> to PCI addresses at this address.  But that's just a "system"
> architecture result, NOT a result of the PCI specification 
> itself.
> 
> David O'Shea
> Intel Corp.
> 
> 
> -----Original Message-----
> From: Parampalli, Niranjana [mailto:niranjana.parampalli@intel.com]
> Sent: Thursday, August 01, 2002 9:23 AM
> To: 'pci-sig@znyx.com'
> Subject: Device at address 0
> 
> 
> 
> I am looking at a PCI implementation which 
> requires BaseAddressReg to be non zero value
> (does not respond if located at 0). I could not
> find anything relevant in PCI (2.3) that precludes
> relocating device to Address 0. Any thoughts?
> 
> Thanks,
> -n.p.
> 

-- 
-- Neal Palmer

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