Subject: Re: FDDI: PC/BIOS and MTU
To: Hal Murray <>
From: Manuel Bouyer <>
List: current-users
Date: 05/31/1999 17:02:44
On Sun, May 30, 1999 at 05:11:34PM -0700, Hal Murray wrote:
> Is anybody using DEFPAs on PCs? 
> They work on Alphas. 
> When I tried them on Compaq Deskpros, nothing good happened.  I finally 
> tracked it down to the PCI_COMMAND_MASTER_ENABLE bit not being set 
> in the main CSR.  That's the DMA enable flag.  As you can probably 
> guess, nothing good happens when that's not turned on. 

I have got to deal with these machines as well. You have to turn on
DMA manually for each board in the BIOS (default is off, even for
Compaq netelligent (intel based) boards ! :)

> I don't know much about PCs.  Who is supposed to turn that bit on?  
> Is this just a glitch in this BIOS or will most PCs have the same 
> problem?  The PCI section of the F10@powerup setup code recognizes 
> the card enough to say "FDDI". 

The BIOS is supposed to turn it on, though some driver explicitely set the
bit to '1', just to be sure.

Manuel Bouyer, LIP6, Universite Paris VI.