AGP aperture memory and 32bit binaries + NVIDIA

[aenertia]

Hi all,

I have noticed that running cedega ( a 32bit program) that it is only able to see upto 32mb of agp memory (this refers to agp aperture size).

Now I have a 256mb fx5600, and bios is set to 128mb aperture.

After playing around with various bios aperture sizing I have notices that increasing the agp apperture size over that 128mb acctually decreases the amount of addressable agp memory for cedega 256mb reduces it to 24mb and 512mb reduces it to 8.

reducing the memory has similar effects set to 64 I get 16mb available. and set to 32 I get no video from console nor X.


After reading through bits and peices and being a veteran of video issues both ati and nvidia, my proc mtrr is all in order and amd64 native games such as ut2004 address the full available agp apperture memory...

However 32bit games can't allocate this. This leads to massive performance loss under cedega, and some performance loss in doom3 (native) and quake4 (native).... Huh so much for not needing to port to 64bit for amd64....

My Total system memory is 2gig. And I believe this may be where the problem lies.

I am guessing that the reason I get reductions in reported agp apperture/mem to 32bit is that the kernel is only allocated X ammount of the address ranges into the 32bit memory range. 128mb seems to be optimal for some reason, mapping 32mb into low memory that is addressable by 32bit binaries.

Now this is just a hunch... I need someone to confirm this behaviour with a similar system.

I am running on a via KT800 chipset, with an opteron 248.

Can someone confirm this same behaviour with there amd64 rig please.


before you suggest it. I have tried both in kernel agpgart and nvidia agpgart... no difference.

I have also tried playing with framebuffer memory allocation in the hope that forcing the vesafb size might force more of the agpgart to go into 32bit addressable space... no luck.


As I said this is a hunch... but it makes sense to me.

BTW I am using nitro-1 with 2.6.16-rc3 kernel. This is using the default 1g/3gb memory split patch that (ithink) is in mainline.

Any comments or suggestions appreciated.

I am going to try booting with mem=900 now to see if limiting system mem free's up addressable space... Will let people know the outcome.



Kind regards

Joel W (AEnertia)
_________________
IM is Good.

[aenertia]

http://transgaming.org/forum/viewtopic.php?t=4981

Looks like a known bug....

NVIDIA Issue so may be barking up the wrong tree... although I am guessing my diagnosis is still correct.
_________________
IM is Good.

[RzRSpitFire]

Ive noticed a similar thing under ut2004 ,my AGP aperture is 128mb (according to "dmesg | grep agp" ).When i set "VARSize=64" (half agp aperture??) in my ut2004.ini, ut2004.log says Log: OpenGL: allocated X MByte of AGP memory , i say X because it can vary somewhat even with "VARSize=32".I had a look at the help file for /dev/agpgart (AGP Support) in the kernel and it gave me this CONFIG_AGP: │

│ AGP (Accelerated Graphics Port) is a bus system mainly used to
│ connect graphics cards to the rest of the system.
│
│ If you have an AGP system and you say Y here, it will be possible to
│ use the AGP features of your 3D rendering video card. This code acts
│ as a sort of "AGP driver" for the motherboard's chipset.
│
│ If you need more texture memory than you can get with the AGP GART
│ (theoretically up to 256 MB, but in practice usually 64 or 128 MB
│ due to kernel allocation issues), you could use PCI accesses
│ and have up to a couple gigs of texture space.│
│
│ Note that this is the only means to have XFree4/GLX use
│ write-combining with MTRR support on the AGP bus. Without it, OpenGL
│ direct rendering will be a lot slower but still faster than PIO.

Im assuming its something to do with that, i cant see any other relevant info on this subject anywhere
using
os[Linux 2.6.15.i686] distro[Gentoo Base System version 1.6.14] cpu[1 x AMD Athlon(tm) XP 3200+ @ 2.21GHz] mem[Physical : 1010MB,]
all sat on a, VIA Technologies, Inc. VT8377 [KT400/KT600] (Gigabyte 2004 rz M/B) with a, Creative Labs SB Audigy (rev 04) and a, nVidia Corporation NV43 [GeForce 6600/GeForce 6600 GT]