Why the VRAM limit on 780 and Titan?

[Yevrag35]

It's not a limit, per se, but why do they offer cards like the 770 with a 4GB option, but not the same for the 780 or the Titan? The most I've seen were 3GB. I'm just curious, even though games can't go past 4.

 

[steve10765]

While looking for a card, I found some info on the most likely reason why they dont have over 3GB. It would greatly compete with the Titan performance wise, and they would rather have someone buy a titan than a 780 for less $

BTW games can use more than 4gb if you run more than 1 monitor, really high res, and other things like that

 

[PP Mguire]

It's not a limit, per se, but why do they offer cards like the 770 with a 4GB option, but not the same for the 780 or the Titan? The most I've seen were 3GB. I'm just curious, even though games can't go past 4.

The titan has 6GB, actually.

The 780 has 3GB because it is literally a cut down version of the Titan to sell more at a lower cost. The titan is based off the K20 Tesla card, as all it has in difference is a bios able to handle desktop drivers. The 780 is a cut down version of that with the same memory bus width of 384 giving it 3GB of RAM. The 680 and 770 have a 256bit width giving them memory increments of 2 and 4GB.

The other card sharing this same scheme as the brutes is the 580, which is why its lesser version has 1.5GB, while they also offer a 3GB version.

Games can go way past 4GB on resolutions higher than 1080p. It's just not plausible for a few reasons. One being, current console limitations and texture decompression algorithms. Rage had a very unique way of decompressing textures using GPGPU, and that is essentially what the new consoles will do. With this in mind, texture resolution can be much higher converting gigabytes of info in less than a second which would then fill that VRAM.

Other instances like my modded copy of Skyrim running on 1920x1200 was utilizing 3.7GB of a 4GB card. If I was down sampling 2560x1600, had a 4k setup, or was running Surround it would have been much higher. My copy of Skyrim literally brings 2 2GB 680s to their knees in Surround.

 

[Yevrag35]

BTW games can use more than 4gb if you run more than 1 monitor, really high res, and other things like that

Games can go way past 4GB on resolutions higher than 1080p.

I thought because games weren't developed 64bit, that that was precisely the reason why games specifically couldn't handle more than 4GB.

But the reason for making the 780 only 3GB makes sense now.

 

[steve10765]

your thinking of how much RAM the OS can use, VRAM is different

 

[Yevrag35]

your thinking of how much RAM the OS can use, VRAM is different

I thought the 4GB limit for 32bit processes refers to the total addressable memory space, made up of system RAM, graphics RAM, PCI memory range, ACPI and a few other bits and piece, and not just the RAM itself.

 

[PP Mguire]

I thought the 4GB limit for 32bit processes refers to the total addressable memory space, made up of system RAM, graphics RAM, PCI memory range, ACPI and a few other bits and piece, and not just the RAM itself.

That is extendable from a program within a 64bit OS, but I don't think the wall applies for inner communication in hardware. Otherwise, there wouldn't be a point in having a 6GB card like a Titan.

Games themselves don't typically go over 2.5GB of RAM usage due to limitations in consoles, but arguably the main reason is what you explained.

 

[Yevrag35]

Ok, so if a game gets ported over from a console, the developers may do "something" so it can allocate more memory than it was originally designed for?

I also knew native 64-bit programs could go over 4gb, I just thought that most, if not "all" games were still 32bit.

 

[PP Mguire]

Ok, so if a game gets ported over from a console, the developers may do "something" so it can allocate more memory than it was originally designed for?

I also knew native 64-bit programs could go over 4gb, I just thought that most, if not "all" games were still 32bit.

Depends on the engine in question. For the current consoles, they aren't ran on what one would call a native 32bit architecture. Other engines like Cryengine and Unreal can port in real time. The limitations on the consoles are mainly only software, so lifting them isn't too hard.

Certain games can be made to utilize more than their 2GB limitation. For instance, Skyrim can be made to utilize mass amounts of RAM due to its problem with memory leakage. Still, when it hits about 3.5GB of usage after extensive gameplay it likes to be crash happy as the programs really aren't currently made for that.
The newer consoles and engines will change this, as they will all be DX11 and 64bit native with multi-threaded and GPGPU in mind during development, not an afterthought.