Mike A. Harris wrote: > On Wed, 12 Jun 2002, David S. Miller wrote: > >> Date: Wed, 12 Jun 2002 18:08:37 -0700 (PDT) >> From: David S. Miller <[EMAIL PROTECTED]> >> To: [EMAIL PROTECTED] >> Cc: [EMAIL PROTECTED] >> Content-Type: Text/Plain; charset=us-ascii >> Subject: Re: [Dri-devel] Default AGP mode >> >> From: "Mike A. Harris" <[EMAIL PROTECTED]> >> Date: Wed, 12 Jun 2002 20:35:15 -0400 (EDT) >> >> It would appear that AGP mode 1x is used by default always unless >> the AGPmode option is specified in the config file. (Correct me >> if I'm not completely correct with that). >> >> I'm wondering if the default can be changed to be "the fastest >> sane mode supported by the hardware and/or configured by the >> BIOS". >> >> In fact it's wrong when the user has selected a different mode from >> the BIOS setup especially on chips where we do not know how to fully >> program the hardware when switching modes correctly. > > > Indeed. I just wasnt aware of the specifics of how things are > currently done, and wether or not it is being done both optimally > and safely. Stability trumping performance of course. ;o) > > >> I think the default should be whatever mode the chipset is in >> when AGP is started. > > > Agreed, that was my opinion as well. I just wasn't 100% sure how > it is currently defaulting, and I figured I'd ask here prior to > examining the source code. Having the BIOS default to say 2x, > and having X default to 1x, or worse, having the BIOS default to > 8x and X default to 1x or 2x is the situation that I'm curious to > determine if we're avoiding, or if it is a chipset specific > thing, etc. > > Basically, someone has asked for me to default AGPMode to 4 in > our config file, which I thought was absolutely crazy. The claim > is that AGP defaulted to 1x, but changing it to 4x sped things up > dramatically. That is what lead me to believe that the "default" > being used is not the BIOS setting. > > I'm going to explore the source code tonight, and see what if > anything I might be able to poke around. > > Thanks for the feedback David. > > > Actually, its most safe to default to AGP mode 1x. If we aren't switching modes correctly there is a bug in that agp driver, and I'd like to know about it. Unforunately there is no real way to test if anything above AGP mode 1X works correctly. Defaulting to AGP mode 1X is the best option, since AGP mode 2X might cause the machine to lockup upon initiating a DMA request. Certain card/motherboard combinations just don't work above 1X.
The default is there for a reason. Its the only real safe value. If we knew how to recover each card from a hang it might make sense to make up some sort of test during installation that discovers the best mode (I think this is how some windows drivers work). However we don't know how to do that for the most part, and it has to be accomplished for all hardware. Just add some options to the X config tools in RedHat that deal with it an allow the user to select and give them a HUGE warning that it might lock their machine above 1X. Thats probably the best solution if you want to allow them to configure this option. Anyway, that should sum up the previous discussions on the topic... -Jeff _______________________________________________________________ Sponsored by: ThinkGeek at http://www.ThinkGeek.com/ _______________________________________________ Dri-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/dri-devel
