setting AGP mode in fglrx?

[aaso]

is it possible to set the AGP mode of ATI cards?

currently my AGP device gets set to 8x, but then my hardware freezes, both on WINXP and Ubuntu,

I was wondering if I could force this to 4x, because then my 3D won't freeze within moments

[grim42]

I don't think this can be set in the current Linux ATI drivers. There may be a BIOS setting you could try?

What video card do you have -- is it 4x or 8x? What does the motherboard support? Are you sure that this is the reason it's freezing?

[aaso]

No I can't set it in BIOS unfortunately..

it's a VT8377 KT400 AGP host, so it should accept up to 8x

the card itself is a mobility radeon 9700 and should also be 8x

I never succeeded in running it 8x tho, not even with most
recent catalysts available, once set to 8x it will crash any
3D app I try to run within a couple of seconds. I will get
acceleration but almost instant freeze as well. Complete lockup,
hard reboot needed.

Once I set the AGP to 4x under Windows, the app/game will
keep on running with nice accel. And my laptop won't crash.

So I'm not 100% sure it's this, but I reckon it's where I need
start looking when downgrading AGP means no crash.

[grim42]

Is this a laptop?

I would assume that a laptop should work at 8x if that's the hardware it comes with. It could be a fault with the hardware?

Unfortunately I don't know a lot about the settings for the ATI drivers. I suspect this may require some kernel config changes or using a different agpgart module.

See this "Linux ATI Radeon Howto" link which mentions AGP 8x and 4x, specifically with reference to a VIA KT400 chipset.

http://www.linux-gamers.net/modules/wfsection/article.php?articleid=22

[aaso]

yeah thanks for the link; it mentions the problem indeed for the KT400 chip, but in combination with the 2.4 kernel? in 2.6 it should be working properly, and that's what it does, I don't get errors i just get a hard freeze..

It probably is hardware related, I've stumbled across some not-linux-related discussions about the graphic card itself running agp 8x, stating this doens't work so well in practice as it does in theory

[aaso]

I suspect this may require some kernel config changes


like in the character devices?

would it be possible to force the agp to V2 instead of V3 (8x)

i'm at work so I can't try yet but I'm dying to know the answer

[grim42]

What I meant was possibly having to recompile the kernel with some different config options -- I'm only guessing though.

There must be a way to force v2 instead of v3 but I don't know what it is -- sorry that I'm not being terribly helpful.

Try posting your question in the Hardware Help section -- there's probably someone there who knows more about this.

[aaso]

Someone found the following for me, and it works!

http://www.abit-usa.com/products/graphics/documents/agp30_final_10.pdf
From the table in the documentatin page 49, bit 0:2 are controlling the AGP mode. Using the AGPMask option, you can change the mode by masking those bits.



AGPMask:
0x00000001 = AGP 1x disable (force 2x and/or 4x)
0x00000002 = AGP 2x disable (force 1x and/or 4x)
0x00000004 = AGP 4x disable (force 1x and/or 2x)
0x00000010 = fast writes disable
0x00000200 = Sidebanding disabled

AGPv3Mask:
0x00000001 = disable AGP 4x (force 8x)
0x00000002 = disable AGP 8x (force 4x)

So the last option was the one I needed...thanks for thinking with me!

[grim42]

Hey that's great to know! Thanks for the feedback -- this might come in handy sometime for me too!