AGPx8 and AGP Fast Write. Is it a kernel option? [SOLVED]

[Daniel Tourde - Caelae.se]

Hello,

I am trying to get AGPx8 and FastWrite working on my machine. The options are enabled in the BIOS but I suspect my card is still in AGPx1 (Radeon 9250) and FastWrite makes X11 crashes... (see http://forums.gentoo.org/viewtopic-t-46 ... t-agp.html)

I ask all the kernel gurus around... Is there a special flag/option I am supposed to use in the kernel to get AGPx8 and FastWrite working?

Daniel

[Daniel Tourde - Caelae.se]

By adding the AGP mode in xorg.org, I got x8 (instead of apparently x4 by default)

Section "Device"
Identifier "Card0"
Driver "radeon"
Card "** ATI Radeon (generic) [radeon]"
Option "AGPMode" "8"
# Option "AGPFastWrite" "true"
EndSection

grep AGP /var/log/messages
Jun 3 17:39:17 mhordraid agpgart: X tried to set rate=x12. Setting to AGP3 x8 mode.
Jun 3 17:39:17 mhordraid agpgart: Putting AGP V3 device at 0000:00:00.0 into 8x mode
Jun 3 17:39:17 mhordraid agpgart: Putting AGP V3 device at 0000:01:00.0 into 8x mode

However FastWrite still crashes X11. Any idea? The optiion is on in the BIOS but what about the kernel? Am I supposed to do something there?

[Daniel Tourde - Caelae.se]

Mea culpa....

I foudn out why I cannot get FastWrite. My card and my motherboard have it but I have a VIA chipset which seems to be known not to have very good FastWrite behavior
The following document explains very well the issue (see the tweak the performances section)

http://www.gentoo.org/doc/en/dri-howto.xml

My mother board accepts Fast Write (see the FW+)
lspci -vv
00:00.0 Host bridge: VIA Technologies, Inc. PT894 Host Bridge
Subsystem: ASUSTeK Computer Inc. Unknown device 8199
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
Status: Cap+ 66MHz+ UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort+ >SERR- <PERR-
Latency: 8, Cache Line Size 08
Region 0: Memory at d0000000 (32-bit, prefetchable) [size=256M]
Capabilities: [80] AGP version 3.5
Status: RQ=32 Iso- ArqSz=0 Cal=2 SBA+ ITACoh- GART64- HTrans- 64bit- FW+ AGP3+ Rate=x4,x8
Command: RQ=1 ArqSz=0 Cal=0 SBA+ AGP+ GART64- 64bit- FW- Rate=x8
Capabilities: [50] Power Management version 2
Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
Status: D0 PME-Enable- DSel=0 DScale=0 PME-


01:00.0 VGA compatible controller: ATI Technologies Inc RV280 [Radeon 9200 PRO] (rev 01) (prog-if 00 [VGA])
Subsystem: Connect Components Ltd Unknown device 2801
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B-
Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
Latency: 64 (2000ns min), Cache Line Size 08
Interrupt: pin A routed to IRQ 177
Region 0: Memory at b0000000 (32-bit, prefetchable) [size=256M]
Region 1: I/O ports at c800 [size=256]
Region 2: Memory at ff5f0000 (32-bit, non-prefetchable) [size=64K]
Expansion ROM at ff5c0000 [disabled] [size=128K]
Capabilities: [58] AGP version 3.0
Status: RQ=256 Iso- ArqSz=0 Cal=0 SBA+ ITACoh- GART64- HTrans- 64bit- FW+ AGP3+ Rate=x4,x8
Command: RQ=32 ArqSz=0 Cal=0 SBA+ AGP+ GART64- 64bit- FW- Rate=x8
Capabilities: [50] Power Management version 2
Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
Status: D0 PME-Enable- DSel=0 DScale=0 PME-

BUT...
Warning: Enabling AGPFastWrite on a VIA chipset will very likely cause your machine to lock up. VIA chipsets do not play nicely with fast writes, so use this setting at your own risk.