Memory with multiple Cards

[cfrank78]

Hello Guys!

I have 3 Cards.

1: my old 560TI overclocked 1024mb
2: gtx 660ti extremely overclocked 2048mb
3: gt640 slightly overclocked as pure display card - also 2048mb

I use 560 and 660 for rendering, but the standalone just shows 1023/1023 ram. Should not there be written 1024/2048? I am confused!

I wanted to attach a picture, but everytime i tried to upload just a message like: Could not upload attachment to ./files/73306_08b9d762933e6d46c12ceaa8f7e4181b. shows up. I think you understand anyway what i mean.

is this normal or why is that strange behaviour with the ram?

Kind regards Chris!

[mib2berlin]

but the standalone just shows 1023/1023 ram

This is correct, the VRam of to cards is not added.. the whole scene must fit into both cards.
If you use a 1 GB and a 2 GB card Octane can only use 1 GB.
If you have bigger scenes you have to use the GTX 660Ti alone (or with GT 640) to use the 2 GB.

BTW. It is not advised to extremely overclock cards for Octane, watch your GPU temperatures!

Cheers, mib.

[cfrank78]

This is correct, the VRam of to cards is not added.. the whole scene must fit into both cards.
If you use a 1 GB and a 2 GB card Octane can only use 1 GB.
If you have bigger scenes you have to use the GTX 660Ti alone (or with GT 640) to use the 2 GB.

BTW. It is not advised to extremely overclock cards for Octane, watch your GPU temperatures!

Cheers, mib.

Hey Mib!

Thank you very much for your reply.

The 660 TI is overclocked from stock and runs at full load at 79 degrees. the 660 is 95 degrees LOL.

So if i understand you right....even if i have 3 gig available - octane just used 1 gb? why is that. what for example i would build a second gtx660ti in my rig. both cards would have 2048mb ram. will octane then use 4096 or just 2084 of one card?

Thank you very much for your help.

Kind regards - Chris!

[mib2berlin]

for example i would build a second gtx660ti in my rig. both cards would have 2048mb ram. will octane then use 4096 or just 2084 of one card?

Octane use the 2048 on both cards but don´t add it to 4096.
If you start rendering Octane load the scene, textures in the memory of each card and the GPU starts processing.
Think about a scene with 1.5 GB size and upload it to a 1 and a 2 GB card, this don´t work.
But thats because Octane is so fast.

Cheers.

[cfrank78]

Octane use the 2048 on both cards but don´t add it to 4096.
If you start rendering Octane load the scene, textures in the memory of each card and the GPU starts processing.
Think about a scene with 1.5 GB size and upload it to a 1 and a 2 GB card, this don´t work.
But thats because Octane is so fast.

Cheers.

So to make it clear!

Octane will allways take the lowest value of a card. if you have for example a 1 and a 4gb card, octane will use 1 gb of BOTH cards - so 2 gb complete. Is that right?

if i would have for example two 2gb cards, then octane would use all 4 gb - 2gb of each? right?

and...last question. if i would have had a scene with about 3gb and built in 2 2gb cards....will octane give 1.5gb to the one card and the other 1.5 gb to the other?

Thank you!

Chris!

[face]

The only thing which should you know is:
Your complete scene must fit into the VRam of the card with the lowest amount of VRam.

This is because Octane can´t transfer data between the cards.
If your scene is 3GB and you have a 2GB and a 4GB card, only the 4GB card can handle the complete scene.

face

[cfrank78]

This is because Octane can´t transfer data between the cards.
If your scene is 3GB and you have a 2GB and a 4GB card, only the 4GB card can handle the complete scene.

Hi face!

So if my scene is bigger than 4gb - i am fu.... up, right? *lol*

If i understand you right......when i want to have for example 4 pcie cards in my computer, all of the 4, which i wanna use for rendering, must have 4gb, cause if i just had 1 with 1 gb - i can only use 1gb. so - bying 4 cards with 4gb is pretty expensive....and at least i could use anyway just 4gb - do i understand that right. sounds very.......hm......strange. pay a lot of money for 4gb cards.....and you have 16gb af vram, but only can use 4gb. hmmmmmmmmm!

Kind regards Chris!

[face]

That is correct.
Have heard that earlier some programs are running on 640KB
See it as challenge to fit your scene in 4GB.
With a second 4GB card, you pay also only speed, not VRam, same as a dual processor...

face

[mib2berlin]

Hey face, very good comparison, each CPU use its own cache.


Cheers, mib.

[cfrank78]

That is correct.
Have heard that earlier some programs are running on 640KB
See it as challenge to fit your scene in 4GB.
With a second 4GB card, you pay also only speed, not VRam, same as a dual processor...

face

Hi Face!

I have no problem to pay the speed. Why? Cause there are several 2048mb gtx680 with a very good price (400 euro) which are OC and fast as hell. But i cannot use them, cause if i would use it, i loose 2gb. The 4gb gtx680 are much more expensive AND.....useless, cause i cannot use the ram anyway. so ........i pay the speed with much more money than it should be. I have to pay much more than it would really be necessary. 1 card 4gb and rest 2gb for speed, but with 2048 possible, would be great....but it sounds like this is impossible.

Imagine a rig with 8 gtx 680 cards watercooled (1 slot). This is for example possible in one of the gigabyte boards. 8 x €525,- = € 4200,- instead of 1 x 525,- (4gb card) + (7 x 400,- (2gb cards)) = 3325,- so you would save 875 Euro. For me thats a LOT of money. You pay 875 more, with not more speed. pretty useless from my point of view....but hey....you have 32 gig of vram instead of 18 and you can use 4 gig from it.
ahm..........so.........hum......!!!

Kind regards Chris!