RE: Subsystem Vendor ID

["James Lam(SC)" <james.lam@o2micro.com>]

   Most of the VGA chips (may be all) which support Vendor and Subsystem
Vendor ID would put them in the ROM or EEPROM. However, if the chip doesn't
need or doesn't has a ROM/EEPROM interface (e.g. PCI-to-PCI bridge), they
normally have a back door for the system to set those registers during power
up. Normally, the chip will also provide a write protect mechanism to
prevent any further changes of those registers. It would be a little bit
more complicated if the chip supports D3 cold state (PCI Power Management).
Since there is no standard for this kind of implementation, you have to
contact the chip manufacturer to get the details.

James Lam.
O2Micro Inc.

> ----------
> From: 	Weng[SMTP:wtx@umem.com]
> Reply To: 	wtx@umem.com
> Sent: 	Sunday, July 09, 2000 4:12 PM
> To: 	pci-sig@znyx.com
> Subject: 	Fw: Subsystem Vendor ID
> 
> 
> 
> Hi,
> By hardware wired I mean it is fixed in any ROM system and only can be
> read,
> not written.
> 
> Weng
> Micro Memory Inc.
> Chartworth, CA 91311, US.
> 
> ----- Original Message -----
> > From: Mikhail Matusov <matusov@squarepeg.ca>
> > To: <pci-sig@znyx.com>
> > Sent: Monday, July 10, 2000 2:34 PM
> > Subject: Re: Subsystem Vendor ID
> >
> >
> > > ----- Original Message -----
> > > From: Weng <wtx@umem.com>
> > > To: <pci-sig@znyx.com>
> > > Sent: Sunday, July 09, 2000 5:08 PM
> > > Subject: Re: Subsystem Vendor ID
> > >
> > >
> > > >
> > > > Hi,
> > > > Vendor ID/Subsystem ID  is hardware wired.
> > > > Actually there is no feasible hardware method to modify what you
> wanted
> > to
> > > > do.
> > > >
> > >
> > >
> > > In most of modern PCI chips it is loadable from an EEPROM as Lloyd
> Bircher
> > > mentioned earlier. I've done this many times.
> > >
> > > It could've been hardwired in older chips and at least in some older
> chips
> > > Subsystem IDs were not implemented at all.
> > >
> > > ============================
> > > Mikhail Matusov
> > > Hardware Design Engineer
> > > Square Peg Communications
> > > Tel.: 1 (613) 271-0044 ext.231
> > > Fax: 1 (613) 271-3007
> > > http://www.squarepeg.ca
> > >
> > >
> >
> 
>