Dual Wielding Video Cards...why?

[=DR.DEATH=]

I was on a forum on another site discussing the possibily of purchasing a second 512MB video card identical to my own and bridging it with my current video card so that i can have 1GB of video memory. But i was told that having a second video card installed into my motherboard will NOT increase my video memory at all.

...So out of curiosity, what is the point then of having more than one video card installed on a motherboard? I could have sworn seeing a picture a couple years ago on this site somebody having three video cards installed in his motherboard.

For heat management purposes i'm going to be replacing my current video card with a single more powerful one but i am still curious.

[=KoS= Eldragon]

There is more to video cards than the amount of memory they have. The GPU (Graphics processing unit) is where all the magic happens.

Graphics rendering is a process that can be run in parallel. The more processors you throw at the problem, the faster you can render the image. Thus having two video cards will be faster than a single one. It does not double your speed, but depending on the game you can see a good 30% gain.

It does not increase video memory because both cards need to share the same video memory in order to process the image. e.g. If card A does the top half a texture, and card B does the bottom, half, they each need a copy of the image in order to do their half.

Until very recently I ran a pair of ATI 4780s in CrossFire. It was blazing fast, yet still shared 512 mb of memory.

[Spooky]

I was on a forum on another site discussing the possibily of purchasing a second 512MB video card identical to my own and bridging it with my current video card so that i can have 1GB of video memory. But i was told that having a second video card installed into my motherboard will NOT increase my video memory at all.

...So out of curiosity, what is the point then of having more than one video card installed on a motherboard? I could have sworn seeing a picture a couple years ago on this site somebody having three video cards installed in his motherboard.

For heat management purposes i'm going to be replacing my current video card with a single more powerful one but i am still curious.

The point of adding another card and putting it into SLI or CrossFire is to increase rendering performance, not to increase the amount of available video memory. You can have up to four video cards in SLI or CrossFire mode, if the infrastructure allows it.

Apart from SLI and CrossFire, you are free to add any amount of independent video cards into your system (depending on a few factors). The main point of that is to have more video outputs, mainly. Either for Desktop applications, or, if supported, even within 3D applications, like Microsoft Flight Simulator.

[=DR.DEATH=]

Cool, thx for the info. That answers a lot of questions for me.

[Come and See]

It's like multi-cpu processors. Better load balance. Instead of one GPU running at 100% performance, you have two splitting evenly at 50%.

[Spooky]

It's like multi-cpu processors. Better load balance. Instead of one GPU running at 100% performance, you have two splitting evenly at 50%.

That's not quite accurate, if that were the case, there would be no performance gain .

[Taemien]

I know with Fallout 3, I could run overmax settings (editing config file to higher then ingame lets you do) with dual Nvidia 8800 GTXs. It ran quite well. However it sucked too much power from the PSU and so I had to run FO3 with a single card and had to dime back those settings a bit.

So you will get a performance boost in some cases. For me I had to disable SLI and one card to play Everquest 2. It didn't support SLI or multiple GPU's at all. And would actually slow down. But that game was made in 2004. Most newer games will run well with Crossfire or SLI.

There was a pic of a setup floating around of a 5 GPU setup, one Nvidia card for the Physix and 4 Crossfired ATI cards. I don't know how well it performed in games. Benchmarks don't tell the whole story these days. Some games will like a setup, some won't. So mileage will vary a bit.

I know MWLL specifically did alright with a dual 8800 setup I had a while back. Though once we were in Warhead... I dunno, I went to a single ATI card before that.

One thing I hate about building computers these days, you buy the best you can afford and cross your fingers lol. Though usually a standard high CPU, high GPU and loads of ram will work. Its when you do crazy stuff like SLI or Crossfire, or Eyefinity or whatnot is when stuff may or may not work as intended.

[Defender]

Personally, I have two cards for two reasons. One, to offset Physx to another card where applicable to gain the most performance out of a different card. Two, to have up to 4 monitors.

[Come and See]

It's like multi-cpu processors. Better load balance. Instead of one GPU running at 100% performance, you have two splitting evenly at 50%.

That's not quite accurate, if that were the case, there would be no performance gain .

The performance gain is mostly from your frames being split in two (not-equal) parts between the two video-cards which is more efficient when it comes to loading renders on your screen. Back when it first came out and years after it was a huge performance increase because most mid-range video-cards couldn't handle the ultra-high detail graphic games like Crysis.

Nowadays game designers have started toning their graphics down to the mid-range level because its smart on their part and it seems like video cards are outpacing game graphics.

[Spooky]

I know, but the GPU load will not be just at 50%. Both will not be on 100%, that's for sure.

[Freeborn_Toad]

The performance gain is mostly from your frames being split in two (not-equal) parts between the two video-cards which is more efficient when it comes to loading renders on your screen.

AFR (alternate frame rendering) is actually much more common than SFR (split frame rendering).

[=CJW= Bin Fish]

...So out of curiosity, what is the point then of having more than one video card installed on a motherboard?

For epic e-Peen!

All joking aside I needed the added horsepower to render the game across three screens.

[Priest]

You will find in some of the reviews that two 'lessor' or older model cards could, at times, outperform a better card (with the two together priced cheaper than the more expensive card).  Not that I recommend that, but when pricing is the ultimate driving force for a purchase decision, the few dollars saved for a bit better performance is an option.

[Come and See]

You will find in some of the reviews that two 'lessor' or older model cards could, at times, outperform a better card (with the two together priced cheaper than the more expensive card).  Not that I recommend that, but when pricing is the ultimate driving force for a purchase decision, the few dollars saved for a bit better performance is an option.

It doesn't really seem necessary anymore in today's market. The "high-end" video cards are actually quite powerful now and they're available in the $200-300 range. I have a 6950 (flashed to 6970) and it handles Crysis on ultra-high details, max aa, etc. without a hitch. My dual 5950, dual 8800gts, etc. croaked on it before.

[Mitchpate]

Also worth considering is how much more power a 2nd card uses.  While two lesser cards may be cheaper than one high-end card, their combined power consumption will negate the cost savings in a year or so.