RE: PCI 2.2 spec - Subsystem ID and Subsystem Vendor ID Regs

["O'Shea, David J" <david.j.oshea@intel.com>]

W.J.,
 
An older controller that reserves these fields as 0 will simply
not be 2.2 spec compliant.  
 
Its useability will vary by OS.  
 
For the most part, the BIOS rarely cares about the subsystem vendor ID 
or subsystem device ID.   BIOS are more concerned with device class,
and occasionally with Vendor ID and Device ID.
 
The subsystem ID fields just give software a way to distinguish cards
that use the same Si, but are hooked up differently.  (An example comes
to mind of compatibility problems for Tekram SCSI adapters in some
older systems that employed a Symbios Logic SCSI chip on them.  The
system BIOS could not distinguish the devices on the motherboard from
the devices on the Tekram board and tried to run its system opRom code
on the installed Tekram, and it always failed).
 
So, its hard to note exactly what might go wrong.
 
For the most part, the largest area of problems will be with OS
installations
and driver loads.   The OS is most sensitive to the job of matching driver
code with the correct device.   (Matching OpROM code to the correct device
in the BIOS space is basically the same thing, matching a driver).
 
In most cases, the OS will likely get a driver loaded that will work
properly,
but in some cases, perhaps it will not.  This is dependent on how widespread
the use of your Si on various board assemblies as well as the subsystem ID
fields.
 
Clear as mud?
 
-David O'Shea
 
 
 
 -----Original Message-----
From: Walter Gomes [mailto:Walter.Gomes@computerboards.com]
Sent: Tuesday, February 08, 2000 11:27 AM
To: Mailing List Recipients
Subject: PCI 2.2 spec - Subsystem ID and Subsystem Vendor ID Regs



Hello- 

In the 2.2 spec PCI SIG choose to make using the subject registers
mandatory.  Can it be assumed that older controllers that reserve these
registers and make them 0 will still be useable in systems that check these
IDs and boot time???  Will incompatibility cause BIOS hang ups???
WIN2000/NT config problems???

W. J. Gomes III 
Hardware Engineer 
ComputerBoards, Inc. 
16 Commerce Blvd. 
Middleboro, MA 02346 
Voice: (508) 946-5100 x279 
Fax: (508) 946-9500 
email:walter.gomes@computerboards.com