Sapphire HD3870X2 Low performance

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02-19-2008, 05:38 AM
Kotz

Sapphire HD3870X2 Low performance

Hi Guys

I just recently had to replace my mobo and gfx card as my old ones died on me. I had an Asus A8R-Mvp Socket 939 and a dual Crossfire setup using X1900XTX & XT cards. My new mobo is an Asus A8R32-Mvp Deluxe (latest Bios 0701) and i decided to go for a ATI Sapphire HD3870X2 (8.2 drivers)

Ok so got everything installed and benchmarked my Pc using 3dMark 06 and only got 10356. I was pretty shocked as I got 11500 using only my 1900XTX card.

To make matters worse I love playing Wolfenstein Enemy Territory and the fps is terrible now. On my old setup I had my fps capped at 125, which I got all the time no matter which map I played. Using this new setup my fps spikes to as low as 30 then backup to 125.

I have read on various forums including sapphires own that it could be something to do with whats called Powerplay. Where the 3870X2 cuts power to save power on low 2D/3D resource games/apps. This kind of sucks as there's no fix to knock Powerplay off at the minute. But it doesn't really explain the poor results in 3D Mark 06 i mean I thought i would be getting a lot more here's my system for anyone that could maybe help me out.

Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 2
Processor: AMD Athlon(tm) 64 FX-60 Dual Core Processor, MMX, 3DNow (2 CPUs), ~2.6GHz
Memory: 2048MB RAM DDR2
Soundcard SB X-Fi Audio [BC00]
mobo Asus A8R32-MVP Deluxe (Bios 0701)
750w Crossfire PSU

Oh I have the card connected with the 2 6 pin power connectors the card is running just at normal mhz it's not overclocked.

Thanks for any help, if anyone needs anymore info in order to help me out I'll post it.

Thanks again

Glenn : )
02-19-2008, 05:55 AM
Virous

sounds weird. i have the same card. on a maximus with a q6600 clock in at 3,6ghz. I am using a 6pin+8pin arrangement though. I got 3dm06 18643 as my highest run on 900mhz core on the card.

Check to see if there is no driver left from your old cards, seated right in the PCIEX slot. or if you can try another PSU it may help.

heres the link to my benchmark
http://www.xtremesystems.org/forums/...d.php?t=177043

at stock with those cpus minimum should be 13-14k
02-19-2008, 06:04 AM
Waymon3X6

Also check in GPUZ to make sure that your PCI-e lane is running at 16x, it sounds like it's running at 8x or something right now, which is bottlenecking your performance.
02-19-2008, 06:14 AM
oc_junkY

First thing to do is to get the latest GPU-Z and see if Crossfire is enabled.
02-19-2008, 07:41 AM
Kotz

2 Attachment(s)

Hi Guyz

thanks for the quick posts and trying to help me with this frustrating problem.

Ok I have checked that the cards are indeed running at 16x in the Bios both PCI-E slots on the board are set to 16x.

I downloaded the latest GPU-Z as recommended and here are the results.

Thanks for looking and trying to help
02-19-2008, 08:15 AM
Kotz

1 Attachment(s)

Hi

I was just looking through my Hardware devices and forgot about this PCI device that has a flag against it, don't know if this is something to do with my problems.
02-19-2008, 08:51 AM
MadDias

Quote:

Originally Posted by Waymon3X6

Also check in GPUZ to make sure that your PCI-e lane is running at 16x, it sounds like it's running at 8x or something right now, which is bottlenecking your performance.

what do u guys always have with pcie bandwidth all the time?
his card doesn´t exchange data beween the gpus through pcie.
on the other hand, the card that is bottlenecked by a 8x pcie-lane has yet to be build.
his problem with 3dmark06 is his cpu. @2.6ghz he gets the same cpu score as u intel guys would have with a 1.8ghz c2d.
his score seems right to me. u always have to think about how 3dmark calculates it´s scores. a 3ghz amd x2 is about equal to a 2.4ghz c2d in 3dmark cpu scores.
i score 12k in 3dmark with overclocked 2900´s and a amd @3ghz.

u should monitor ur card clocks with rivatuner. maybe ur card really is reverting to 2dclocks while u are in wolfenstein.
02-19-2008, 09:00 AM
Kotz

Hi

thanks for the input MadDias,so basically you think it's my processor, dam i knew I should have just bought a new mobo and better Intel chip. Thing is why did I get a better score in 3dMark 06 with my old X1900XTX and it wasn't running in Crossfire. I got 11500 with 1900xTX, where as I only get 10356 with newer 3870X2. I'm using same setup apart from newer mobo and gfx card.

Thanks again for all your help n advice I really do appreciate it:up:
02-19-2008, 09:45 AM
jpercel

Kotz I have the same problem with my 3870x2. The card is changing frequency like every 2 seconds midgame going from High 3d mode to Low 3d mode. Its really annoying. All I did was match the frequency and voltage for both modes in the bios and then reflashed the card with my modded bios.
02-19-2008, 10:30 AM
Kotz

Hi jpercel

This card is doing my head in. I'm not really technically minded. I can do the basics when it comes to Pc's but thats it. I thought all I had to do when my pc broke was get a better mobo and gfx card I mean these cards aren't exactly cheap, then to my horror I find my pc actually runs games slower.

Did your bios fix the problem. I'm in to minds whether to try something like a bios update as if I do it and it doesn't work or breaks the card then i can't RMA it back to the supplier.

Why doesn't ATI do something they must know the card has these probs. Wish I'd just gone for a 8800 now:mad:
02-19-2008, 10:40 AM
MadDias

Quote:

Originally Posted by Kotz

Hi

thanks for the input MadDias,so basically you think it's my processor, dam i knew I should have just bought a new mobo and better Intel chip. Thing is why did I get a better score in 3dMark 06 with my old X1900XTX and it wasn't running in Crossfire. I got 11500 with 1900xTX, where as I only get 10356 with newer 3870X2. I'm using same setup apart from newer mobo and gfx card.

Thanks again for all your help n advice I really do appreciate it:up:

11k without crossfire? ur kidding ;)
u are 100% sure that this was a single card at stock clocks?
highest score in the orb with a single x1900xtx is 8755... and that´s with a c2d x6800. i guess ur single card score was more around 6-7k and 11k with crossfire.

u could try reinstalling windows to get rid of the stuff ur old vidcard left on ur system. i had to do this too going from a x1800crossfire setup to my 2900´s.
02-19-2008, 12:14 PM
jpercel

Kotz!

Follow these steps to fix the powerplay issue: I wish ati would fix this though because doing this is a pain in the *** and it MAY void your warrenty.

First download GPU-z 1.7
http://downloads.guru3d.com/GPU-Z-0.....html#download

This tool will allow you to extract your video card bioses..That's right your 3870x2 has two bios files!

When you open Gpu-z it will display your cards info. Next to the bios version number is an arrow. Click it and it will extract the first bios file. Save it to your desktop and rename it "backup0" or whatever. At the bottom of the tool it will give you the option of selecting the second card. Click the down arrow and select the second card then extract that bios to the desktop and name it "backup1" or whatever. Double check the two files: one should be like 44kb and the other should be 64kb. Which ever one is the 44kb file is the (slave) card which we will get into later.

Now that you have those files download the atibios editor
http://www.computerbase.de/downloads...i_bios-editor/

Open each file and change the low power 3d clocks. Make them the same as the high power 3d clocks. Also make the voltage the same. Do not change the 2d or startup clocks unless you want to for some reason. Also make sure your changes are the same for each bios ex. dont make one bios file have a low power 3d frequency clock 300mhz and the other have 400mhz. Save both files under different names like "card0" and "card1" because you want to keep your original bios files in case you screw up your flash. Remember "card0" should be like 44kb because its the slave card.

The bios editor you downloaded should contain the ATI Flash utility.
Next you need to make a windows boot disk in order to get into dos. After your boot disk is created make a folder called "boot" and place the "atiflash" application file in that folder along with the backup bios files and the modded bios files.

Get a pen and paper and write down all your file names from the "boot" folder including their sizes.
card0 = 44kb
card1 = 64kb
backup0 = 44kb
backup1 = 64kb
something to that effect.

Write down the following commands in sequence because you may have to reference them in a "blind flash" This occurs when you flash your bios incorrectly and upon a boot the screen goes blank but everything boots normal. Blind flashing involves booting from your boot disk and typing the commands without being able to see them. That is why you need to write everything down and have your backup files.

Next restart the comp and hopefully your boot disk should take you to the dos prompt.

You should see "A:"
(write down the following commands)

Type "cd\boot" then hit "enter"

Type "atiflash -ai 0" then "enter"
(this command will display the info of your slave card. Make sure file size is about 44kb)

Next type "dir" then hit "enter"
(this will list all the files from your floppy disk. Verify that the file names and extensions match what you have written down. Dos my have displayed the file "backup1" as "b~1". If you blind flash you will use "b~1". Also extensions are files that have like .rom or .bin attached to the name. Ex "card0.rom". If you have extensions then use them when flashing.

Type "atiflash -p 0 card0" or "atiflash -p 0 card0.rom" if you have extensions.
(remember card0 is the name of your bios file)

If the flash was done properly you should see at the end something like "10000kb writen" "10000kb verified".

Now for the master card:
Type "atiflash -p 1 card1"

If the flash was done properly you should see at the end something like "10000kb writen" "10000kb verified".

Thats it your done now just reboot and hope you dont need to do a blind flash.

If you have any doubts or if something is different from what I have written, do not proceed, rather write everything down and post it.
02-19-2008, 03:23 PM
Kotz

Hi

thanks forthat jpercel. I really appreciate you taking the time to explain just how to flash this card,thing is I'm not overly confident I will do it right and can't afford to replace the card. The way my luck is lately I'm sure to screw it up.

Why can't ATI get there dam finger out and release an update, they must know about the problem with this so called top end card.

It's got me really fed up as I rely on my pc so much, just had my leg amputated in september and the computer fills in a lot of my day, you know gaming n stuff.

Ah well I've put at ticket in at Sapphire and ATI see what happens I guess. Hopefully if it's not sorted soon i will just be able to RMA the card back and swap it for a nvidia.

Oh MadDias I'm sorry I have just checked an old book I had my 3dMark scores wrote down in and I got 10930 with one card I'm sure that was with 06 but I may be wrong it was a while ago when I first got my pc.

As always thanks to everyone who has shared some input:up:
02-19-2008, 04:03 PM
jpercel

I have been with nvidia for years. My last card was a 7900gtx and I decided to go with my first ati card ever, the 3870x2. Im starting to regret. Crossfire your fingers for Ati Catalyst 8.3 coming in March.
02-20-2008, 04:20 AM
Kotz

Hi

Just out of interest i decided to pop my old X1900XTX card back into my system today and when i ran a benchmark in 3dMark 06 it came back as 6 thousand and something, so maybe MadDias is right.

Sapphire contacted me about my ticket saying really you need a quad core processor for this gfx card. Wish I knew that before I bought it. Just checked the box and it doesn't say anything about really needing quad core to get the best out of the card.

So the way I'm thinking is I prob would have been better off just buying a cheaper nVidia card which would have gotten me exactly the same performance in my system d'oh!!!!!!

Thing I did notice with my old X1900XTX whenrunning Wolfenstein the performance was just the same as with the 3870X2, almost same frame rate. Now before I put this new mobo and gfx card in I always got 125 (had my game capped at 125) so maybe this mobo is broke too.

Oh I don't know, what I do know is I can't afford to chuck anymore money at this system so it will just have to stay like this until either theres a bios update or I can afford a new monster pc:shrug:
02-20-2008, 04:25 AM
jpercel

I have a quad core as well and my 3870x2 still shuttered until i fixed my bios. I also had a problem where crossfire was not enabled properly so my performance sucked because only one card was being used. Multigpu solutions are very risky because a great deal of games do not have the proper multi gpu support. Crysis is a good example of this.
02-20-2008, 10:26 AM
gOtVoltage

A little input,, Three different 3870x2's and TA770 = 28.8 GB/s because of Mobo Bios

Quote:

Originally Posted by jpercel

I have a quad core as well and my 3870x2 still shuttered until i fixed my bios. I also had a problem where crossfire was not enabled properly so my performance sucked because only one card was being used. Multigpu solutions are very risky because a great deal of games do not have the proper multi gpu support. Crysis is a good example of this.

Oh , if your 3870x2 reads 28.8 GB/s for band width ,, You may have a Bios issue with the Mobo...

Also GPU-Z 0.1.7 is out now:D

http://i168.photobucket.com/albums/u...rra/halfbw.jpg

http://i168.photobucket.com/albums/u...ra/halfbw1.jpg

If your Mobo isnt on the List Below you CAN have a Bios Bandwidth Problem..
This is where the 3870x2 isnt reconized correctly, even though it does seem to work.The Bios runs the card as if it were (8x NOT 16x.)

http://support.ati.com/ics/support/d...asp?deptID=894

You should have 57.7 GB/s at all times even with the card at half speed...Ive contacted Biostar/HIS/Diamond/Visiontek . So it seems to be with the PCi-E link switching ,, DVI/Anolog switching and HTLink 8x,16x (bandwidth) .Some boards the Bios is correct but others it just plain crap !. Its NOW up to the Mobo Vendor to release a working Functional Bios . It Runs like 8x but it is in 16x mode....I can Set the Clocks Manually .Results show that in fact it was running at half B/W(REAL SPEED)..Using only 256mb of memory..WTF..It didnt even seem to be power play causing this ..It would only use 256mb!

Stock @GPU 825mhz and 900mhz memory Both GPU's = 28.8 GB's
Oc @ 904mhz and 2100mhz memory Both GPU's = 33.7 GB's

Ive used AMD GPU tool to raise the Clocks .. Rivatuner and AMD GPUtool Both show full( 16x and Both GPU's and memory overclocked)..

The Biostar Bios on the TA770 is actually limiting the Bandwith on this card..
So if you have a Motherboard that reports 28.8 GB's with a 3870x2 ,See about a Bios update from your Mobo manufactor for the 3870x2 .I happend to have a spare Mobo in which the card would run @ 57.7...For some of you a NEW MOBO may be in order ,That's if you cant wait for the Vendor to get out a Updated Bios.

TA770 dosnt have a updated Bios yet.. Also Ive found that the DVI(Black screen) Happens with the TA770 too..

I had to Use a Anolog/DVi adapter on My Digital LCD....The PCi-E Swicthing mode DVI/Anolog also needs to be updated by Mobo Vendor..

So Far All three cards Did the Same thing on a TA770 a per above,,HIS3870x2// Diamond3870x2// VisionTek3870x2,, im keeping this one for the Lifetime warrenty.

Clearly there is work for Vendors to do...Also My M2N32deluxe..Runs the 3870x2 @ 57.7 GB/s.....With a Phenom :shrug: ! It happens to be on the supported Mobo list go figure!

Note:The 3870x2 @CPU2300mhz is suppose to do better than 12600+.

Remeber @ 256mb = 28.8 GB/s 12500+3Dmark06 is with half the Bandwidth of 512mb NOT 1024mb..Also @ 512mb = 57.7 GB/s you would see 13600/14000+ @2300x4Cpu

http://i168.photobucket.com/albums/u...BiosBW2888.jpg

http://i168.photobucket.com/albums/u.../BiosBW288.jpg

This is unoptimized Bios, Yes Bandwith of only Half of 512mb!
256mb = 28.8 GB/s

This is what its suppose to be @ 512mb!
512mb = 57.7 GB/s

Both Gpu's using everything.:D
512mb per GPU will give you a total of 1024mb =114.2 GB/s..im not saying you use 1024mb total but the Combined power of the 2xGPU+2x512mb in Crossfire..Also the card should read 57.7 while @825/900 and 28.8 while @ 300/450..If it dosnt change and your performance is like having only one 3870 ..No differance between Crossfire AI on or OFF ...

The card may be stuck in low Power switching mode..Ive sent a card back for this already...Its Normal to see 28.8 in low power mode ..CPU-Z @ Idle..But not when your clocks are set manually to 825/900 and in 3Dmode...If it dosnt change there may be a problem!

Its been a long two weeks with these cards already:yepp:

P.S KOTZ ,,Crank up the AA/AF and Resolution,,It will look and play great!
02-20-2008, 11:14 AM
MadDias

Quote:

Originally Posted by gOtVoltage

Oh , if your 3870x2 reads 28.8 GB/s for band width ,, You may have a Bios issue with the Mobo...

If your Mobo isnt on the List Below you CAN have a Bios Bandwidth Problem..
This is where the 3870x2 isnt reconized correctly, even though it does seem to work.The Bios runs the card as if it were (8x NOT 16x.)

the bandwidth reported in gpu-z has nothing to do with the pcie bandwidth...
i can show u a ss of gpu-z on my 2900 @ 8x with a bandwidth of 115gb/s.
the bandwidth shown in gpu-z is only the video ram bandwidth and is affected by the vram clocks and the memory interface.

kotz´s bandwidth is that low, cause gpu-z is using the 2d-clocks of his card to calculate the bandwidth, not the real 3d-clocks.

[QUOTE=gOtVoltage;2785131]
Note:The 3870x2 @CPU2300mhz is suppose to do better than 12600+. [QUOTE]

note that he has an amd... cpu scores around 3k aren´t possible with a amd x2 processor. i´m still convinced that his 10k score (with stock cpu and gpu clocks) is absolutely correct and nothing wrong with it.

[QUOTE=gOtVoltage;2785131]Remeber @ 256mb = 28.8 GB/s 12500+3Dmark06 is with half the Bandwidth of 512mb NOT 1024mb..Also @ 512mb = 57.7 GB/s you would see 13600/14000+ @2300x4Cpu[QUOTE]

what do u mean? more memory, more bandwidth?? not at all...
there is a big difference in bandwidth between a 256bit and a 512bit memory interface. but theoreticaly a 256mb card with a 512bit memory interface can have a higher bandwidth than a 512mb ard with only a 256bit interface.

Quote:

Originally Posted by gOtVoltage

Both Gpu's using everything.:D
1024mb =114.2 GB/s

a 3870x2 doesn´t have a frame buffer of 1024mb. each gpu can only use 512mb of vram. u cannot simply add the vram on the card.
and a hd3870 card with a bandwidth of 114gb/s is hard to find ;) it just doesn´t have the 512bit mem interface of the older 2900 cards. so the bandwidth will always be lower.
02-21-2008, 02:57 AM
HeX_00

Quote:

Originally Posted by jpercel

*GREAT GUIDE*

Just gotta say, thanks for that great flashing guide jpercel!

Did this with my Powercolor X2 last night and it worked a treat!

One thing I did notice though is that both my cards had 64kb BIOS's (according to ATiFlash) but GPU-Z gave me a 44 + 64 BIOS files...

Eitherway, they flashed fine and now my Crysis and UT3 fps problems are gone :up:
02-21-2008, 05:46 AM
Virous

im reading 28.8gbs bandwidth. and i cracked nearly 19k 3dm06. with a sapphire 3870x2??? wth..
02-21-2008, 05:56 AM
jpercel

If your getting that reading from gpu-z then it might be reading the bandw/ of the 2d clocks. Running any 3d application will kick the card's clocks higher, ergo higher bandw/
02-21-2008, 06:53 AM
Kotz

Hey guys

How u all doing??

Well I'm no further forward, have just decided to give up trying to get any better performance out of this old rig. Just a shame I spent quite a bit of money trying to get my machine to try and play Wolfenstein of all games at decsent frames:rolleyes:

I have checked my mobo and it's supposed to be supported so ruled that out. Unfortunately I can't turn up my resolution any more than 1360x768 on my TV/monitor as this might have made the gfx card work a little harder and gotten both processor's to kick in under load. I'll trying turning up the AA/AF and see what difference this makes to game play.

Other than that I guess I'll just wait and see if some revised bios comes out and this helps get me more out of my system.

Thanks for all your help.

Glenn :)
02-22-2008, 01:38 AM
MrMacke

Gr8 guide ^^ altho i used a usb stick to flash :) worked just fine :) b4 flash i got 12k in 3dmark06 and after i got over 16k :D
03-06-2008, 02:00 PM
gOtVoltage

[QUOTE=MadDias;2785229]the bandwidth reported in gpu-z has nothing to do with the pcie bandwidth...
i can show u a ss of gpu-z on my 2900 @ 8x with a bandwidth of 115gb/s.
the bandwidth shown in gpu-z is only the video ram bandwidth and is affected by the vram clocks and the memory interface.

kotz´s bandwidth is that low, cause gpu-z is using the 2d-clocks of his card to calculate the bandwidth, not the real 3d-clocks.

[QUOTE=gOtVoltage;2785131]
Note:The 3870x2 @CPU2300mhz is suppose to do better than 12600+. [QUOTE]

note that he has an amd... cpu scores around 3k aren´t possible with a amd x2 processor. i´m still convinced that his 10k score (with stock cpu and gpu clocks) is absolutely correct and nothing wrong with it.

[QUOTE=gOtVoltage;2785131]Remeber @ 256mb = 28.8 GB/s 12500+3Dmark06 is with half the Bandwidth of 512mb NOT 1024mb..Also @ 512mb = 57.7 GB/s you would see 13600/14000+ @2300x4Cpu

Quote:

what do u mean? more memory, more bandwidth?? not at all...
there is a big difference in bandwidth between a 256bit and a 512bit memory interface. but theoreticaly a 256mb card with a 512bit memory interface can have a higher bandwidth than a 512mb ard with only a 256bit interface.

a 3870x2 doesn´t have a frame buffer of 1024mb. each gpu can only use 512mb of vram. u cannot simply add the vram on the card.
and a hd3870 card with a bandwidth of 114gb/s is hard to find ;) it just doesn´t have the 512bit mem interface of the older 2900 cards. so the bandwidth will always be lower.

What i was saying EXACTLY is a 3870x2 has 57.7GB/s per 512mb of memory at 100%GPU usage..

This in return translates to a total BW or 114GB/s no matter what..

Any One has a 3870x2 with a proper CPU-Z that reads the REAL 57.7GB/s..That is the TOTAL GB/s per 512mb and 1GPU(Not Crossfire) In Crossfire mode this gets multiplied by 2!!!!.Two GPU's and 1mb of memory really is 114gb/s when in CROSSFIRE!..When you overclock the Card say to 900/1100 you should get 70gb/s or more for a Half or 140GB/s for CROSSFIRE both GPU's running 100%..

EXAMPLE :8800GTS has 57.7gb's stock! thats with 256bit. 3870x2 has 2x256bit with 2x57.7GB/s (that means 512mb x 2 in CROSSFIRE MODE 2GPU enabled..

I am in no way making numbers up! The card DOES IN FACT run at 114GB/s for its overall total @100% GPU usage:yepp: In CROSSFIRE EACH GPU uses 512mb = 57.7GB/s stock clocks this means 2xGPU + 2x512mb = 114GB/s and even way higher when Overclocked.

If you are able to read the REAL GB/s with CPU-Z(NOT 28.8GB/s) for both cores you will see what im talking about GB/s wise.
03-07-2008, 11:08 AM
MadDias

Quote:

Originally Posted by gOtVoltage

What i was saying EXACTLY is a 3870x2 has 57.7GB/s per 512mb of memory at 100%GPU usage..

This in return translates to a total BW or 114GB/s no matter what..

Any One has a 3870x2 with a proper CPU-Z that reads the REAL 57.7GB/s..That is the TOTAL GB/s per 512mb and 1GPU(Not Crossfire) In Crossfire mode this gets multiplied by 2!!!!.Two GPU's and 1mb of memory really is 114gb/s when in CROSSFIRE!..When you overclock the Card say to 900/1100 you should get 70gb/s or more for a Half or 140GB/s for CROSSFIRE both GPU's running 100%..

EXAMPLE :8800GTS has 57.7gb's stock! thats with 256bit. 3870x2 has 2x256bit with 2x57.7GB/s (that means 512mb x 2 in CROSSFIRE MODE 2GPU enabled..

I am in no way making numbers up! The card DOES IN FACT run at 114GB/s for its overall total @100% GPU usage:yepp: In CROSSFIRE EACH GPU uses 512mb = 57.7GB/s stock clocks this means 2xGPU + 2x512mb = 114GB/s and even way higher when Overclocked.

When you are able to read the REAL GB/s with CPU-Z(NOT 28.8GB/s) you will see what im talking about GB/s wise.

do u know anything about sli or crossfire?
u can´t simply add vram of two graphic cards (i.e. 2x512mb=1gb vram). each gpu only has 512mb available as framebuffer. one gpu can´t make use of the vram of another gpu. no matter if it´s two separate cards, or two gpus on one card. that´s why each gpu only has acces to the vram at 57.7gb/s bandwidth. the bandwidth doesn´t multiply.
adding up vram also wouldn´t make much sense. think of alternating frame rendering as a simple form of crossfire. in this mode every gpu renders one complete frame of the game. what would happen if gpu1 would use 800mb of the "total" 1gb vram available? gpu2 would only have 200mb left to render the next frame and u would experience extreme flickering and a very bad performance.
i hope u got was i was trying to tell u. having two gpus doesn´t make one gpu have a bigger framebuffer, or having more memory bandwidth. it´s just two graphic cards shareing the work. both at their own speed, with their own memory.

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