let's make it clear once and for all

[Zantal]

SLI configurations don't add up memory

if you have 2 gtx 260 with 800MB vram your total vram will be 800MB

and not as many think 1.6GB

if you have 2 cards of the same model but different memory size the actual total vram will be the lowest of the 2 cards

e.g 1 card with 512 mb and another with 256 = vram 256 MB

just wanted to make it clear as many ppl thinks vram adds up in sli configurations

[freeagent]

good, glad to see nothing has changed with sli in the past ohh 4 years or so

[Badbonji]

Well this could change if lucid hydra comes, been waiting a year for it now :(

[ChanceCoats123]

So is that the same ammount per GPU? Because It wouldn't work too well adding it up as both gpu's would then have to pull from the same vram, or say that gpu 1 uses 5% more ram on occasion. Both gpus are using 500mb out of 512 each, Gpu 1 then can continue to eat up its ram and THEN it has to fetch from the its sli brother. That would make for very high cpu<-> latencies.

[necrokiller]

So what adds up in SLI? Just the memory bandwidth?

[Zantal]

So what adds up in SLI? Just the memory bandwidth?

processing power. nothing more.

i think that the vram is identical for each of the 2 gpus

it's just a copy of the same image in both memories

not even the mem bandwidth.

[Zantal]

Well this could change if lucid hydra comes, been waiting a year for it now :(

gonna google that and see what you are talking about m8 =)

[Zantal]

badbonji if something like that comes out in less than one year my next system must have something like that on it Oo

[jason4207]

Each GPU needs its own memory pool. Let's say AFR method is used. GPU1 renders frame 1, and GPU2 renders frame 2, etc.

For GPU1 to render frame1 it needs all the texture data in its local memory. Anything that can't fit in there is going to have to be pulled from the system RAM (not the other card) and will cause slow-down.

When GPU2 renders frame 2 its going to need almost all the same texture data to do so. This is why the video-RAM banks from each card end up being filled w/ identical data. The data is not mirrored it just happens to be almost identical b/c both GPUs are rendering nearly identical frames.

Processing power goes up as more GPUs are added, but the amount of usable available memory stays the same.

Cards like the 1.8GB 275, and the 1GB 9800GTX+ suddenly have a valid niche when they are used in SLI.

[DUSNOETOS]

I know that this is the Nvida side of things......but does CrossFire treat memory in a similar fashion?

[Zantal]

I know that this is the Nvida side of things......but does CrossFire treat memory in a similar fashion?

ofc =)

[jason4207]

I know that this is the Nvida side of things......but does CrossFire treat memory in a similar fashion?

Yes

[Neuromancer]

The vram does add up towards the addressable memory limit in 32bit operating systems though yes?

[freeagent]

The vram does add up towards the addressable memory limit in 32bit operating systems though yes?

you bet :beer:

[necrokiller]

I am talking to this complete nutcase. He believe if you crossfire TWO 4870x2 he will get 4Gb vram. How the hell do I explain this to him.... is there a link to some article that I can shut him up with?

[Exige]

I am talking to this complete nutcase. He believe if you crossfire TWO 4870x2 he will get 4Gb vram. How the hell do I explain this to him.... is there a link to some article that I can shut him up with?

Uhh, this one? lol. This rule applies to Crossfires as well.
Link him here and tell him to tell the 5-8 people in this thread that they're wrong :P

[necrokiller]

Hahaha he says he has been changing gpus alot and knows more. has 15 years of experience... and that the Windows Video memory panel displays the total memory and it proves that memory it doubled. haha quite an amusing character I must say. I even linked him to this, and there cant be a more simpler explanation: http://nvidia.custhelp.com/cgi-bin/nvidia.cfg/php/enduser/std_adp.php?p_faqid=153&p_created=1101314489&p_sid=e8mBPa9i&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX 3Jvd19jbnQ9MTI3JnBfcHJvZHM9MCZwX2NhdHM9MCZwX3B2PSZ wX2N2PSZwX3NlYXJjaF90eXBlPWFuc3dlcnMuc2VhcmNoX2Zub CZwX3BhZ2U9MSZwX3NlYXJjaF90ZXh0PWRvdWJsZSBtZW1vcnk gc2xp&p_li=&p_topview=1

[rainless]

SLI configurations don't add up memory

if you have 2 gtx 260 with 800MB vram your total vram will be 800MB

and not as many think 1.6GB

if you have 2 cards of the same model but different memory size the actual total vram will be the lowest of the 2 cards

e.g 1 card with 512 mb and another with 256 = vram 256 MB

just wanted to make it clear as many ppl thinks vram adds up in sli configurations

The only thing that's "once and for all" is DEATH. :)

[Zantal]

Hahaha he says he has been changing gpus alot and knows more. has 15 years of experience... and that the Windows Video memory panel displays the total memory and it proves that memory it doubled. haha quite an amusing character I must say. I even linked him to this, and there cant be a more simpler explanation: http://nvidia.custhelp.com/cgi-bin/nvidia.cfg/php/enduser/std_adp.php?p_faqid=153&p_created=1101314489&p_sid=e8mBPa9i&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX 3Jvd19jbnQ9MTI3JnBfcHJvZHM9MCZwX2NhdHM9MCZwX3B2PSZ wX2N2PSZwX3NlYXJjaF90eXBlPWFuc3dlcnMuc2VhcmNoX2Zub CZwX3BhZ2U9MSZwX3NlYXJjaF90ZXh0PWRvdWJsZSBtZW1vcnk gc2xp&p_li=&p_topview=1

ok this is what you do.

take one of his gpus out of the case and smash it right on his teeth

then yell

SEE ******* IT DOESN'T ADD UP U MORON

he will most probably believe you then

[Exige]

Hahaha he says he has been changing gpus alot and knows more. has 15 years of experience... and that the Windows Video memory panel displays the total memory and it proves that memory it doubled. haha quite an amusing character I must say. I even linked him to this, and there cant be a more simpler explanation: http://nvidia.custhelp.com/cgi-bin/nvidia.cfg/php/enduser/std_adp.php?p_faqid=153&p_created=1101314489&p_sid=e8mBPa9i&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX 3Jvd19jbnQ9MTI3JnBfcHJvZHM9MCZwX2NhdHM9MCZwX3B2PSZ wX2N2PSZwX3NlYXJjaF90eXBlPWFuc3dlcnMuc2VhcmNoX2Zub CZwX3BhZ2U9MSZwX3NlYXJjaF90ZXh0PWRvdWJsZSBtZW1vcnk gc2xp&p_li=&p_topview=1

Tell him that even though he has 15 years of experience, Crossfire certainly hasn't been available that long. (At least not to the public.) Nor SLI.

Doubt that will help. Just tell him he's right. Then don't talk to him ever again, I hate people like that :P

[iLoki]

With SLI the card's VMEM has to match. The clocks can be different, they will run to the lowest common denominator. CrossfireX you can mix and match memory sizes and they will work with eachother. Unfortunately, SLI is not that flexible, (unless this has changed in the last few driver releases)

I'm gonna guess exige, that your friend is using vista and has in the order of 4-8gb of memory? If so, windows vista takes a portion of your main system memory and allows it for use as vmem, as a just in case kinda thing. It will not be used unless you run out of memory on your card. (i.e. a 1gb card such as the 4870 will show anywhere from 2 to 4gb of vmem in vista, depending on what the total system memory is)

*edit*
This is how vista calculates the amount of shared video memory:

MAX((TotalSystemMemory - 512) / 2), 64MB) (essentially whichever is Larger)

So, if your friend has say, 6GB of memory, thats (6144-512)/2=2816. Add that to your 1gb video card and you get: 3830MB.

you can download the whitepaper with this info here: http://www.microsoft.com/whdc/device/display/graphicsmemory.mspx

along with the sli/crossfire info, show that to your friend =)

[necrokiller]

Tell him that even though he has 15 years of experience, Crossfire certainly hasn't been available that long. (At least not to the public.) Nor SLI.Doubt that will help. Just tell him he's right. Then don't talk to him ever again, I hate people like that :P

He was getting on my nerves. To top it, he was serious about it and wasnt saying all that for the heck of it. You can all imagine. I told him that he's wasted 15 years of his life. Even told him what iLoki said, even though hes on XP. Heres one of his last msgs:

Ok bro if ur right then too My configuration is more secure according to ya it becomes4870x2 2gb on a single one so if u will xfire ur card then ur video memory will remain 512 still not secure right! on 4870 512 mb but 4870 is two gb now dont say a single 4870x2 is one gb!

talking rubbish with poor grammar. I really only understood the last few words. And by 'secure' hes trying to say 'future proof'. And his last message after my failed attempts to clear his confusion:

I am senior than u in this field and these are my final words..................


*kills himself*

[jason4207]

I didn't understand a single word of that. Is English a 2nd language for him?

[necrokiller]

yes it is. sometimes hes talking about 4870, other times the 4870x2 and then he mixes them up and writes one instead of the other. Thats 15 years of experience right there for ya. bet he writes reviews on newegg too haha

[Exige]

With SLI the card's VMEM has to match. The clocks can be different, they will run to the lowest common denominator. CrossfireX you can mix and match memory sizes and they will work with eachother. Unfortunately, SLI is not that flexible, (unless this has changed in the last few driver releases)

I'm gonna guess exige, that your friend is using vista and has in the order of 4-8gb of memory? If so, windows vista takes a portion of your main system memory and allows it for use as vmem, as a just in case kinda thing. It will not be used unless you run out of memory on your card. (i.e. a 1gb card such as the 4870 will show anywhere from 2 to 4gb of vmem in vista, depending on what the total system memory is)

*edit*
This is how vista calculates the amount of shared video memory:

MAX((TotalSystemMemory - 512) / 2), 64MB) (essentially whichever is Larger)

So, if your friend has say, 6GB of memory, thats (6144-512)/2=2816. Add that to your 1gb video card and you get: 3830MB.

you can download the whitepaper with this info here: http://www.microsoft.com/whdc/device/display/graphicsmemory.mspx

along with the sli/crossfire info, show that to your friend =)
I think you confused me with Necrokiller >.>


He was getting on my nerves. To top it, he was serious about it and wasnt saying all that for the heck of it. You can all imagine. I told him that he's wasted 15 years of his life. Even told him what iLoki said, even though hes on XP. Heres one of his last msgs:

talking rubbish with poor grammar. I really only understood the last few words. And by 'secure' hes trying to say 'future proof'. And his last message after my failed attempts to clear his confusion:

*kills himself*
Lol. That sucks man. Like I said before, I'd just let it go, idk how your friendship is with him, if he's just an acquaintance or a best friend, but he sounds like a truly stubborn prick. :P

[necrokiller]

No hes not a friend. hes that kinda person who likes to pretend he knows everything. All this conversation was actually on another forum. But a greater part of that thread is another language so you guys wouldn't understand what hes saying. And he is one of the 'respected' people on the forum based on his knowledge.

Yes, I make the forum sound horrible but its actually not that bad at all. Alot of people do know what they're talking about. The reason I joined those forums was because I had no idea such a community was present in my native country dedicated to computers/gaming/overclocking. And just to give you an idea, a member of that forum was honored with the Guru3d Rig of the Month for April 2009. You can check it out here, its pretty sick!!!

http://www.guru3d.com/article/guru3d-rig-of-the-month--april-2009/

http://www.guru3d.com/imageview.php?image=17428