Hey, guys, heres some interesting tests: when shadows set to ultra, game engine use 500 mb of vram just on fresh start in main menu! When level isn't even loaded! When shadows are set to high - just 200 mb of vram usage on fresh start. So, ultra shadows mode is not optimized at all and waste of vram and performance. Plus I had stuttering issue almost all the time with it. It's buggy as hell! 500 mb of vram usage with ultra shadows set just in main menu (where nothing is drawn - just skyrim logo) - it's a [censored] joke!

It uses more than 500mb as soon as the game starts so what difference does it make? Ultra shadows with 4xMSAA and light FXAA with the injector mod use anywhere from 700mb to 1050mb of vram in my experience with a 5850 1gb, as a result every once and a while in demanding vram areas I get a slight stutter when quickly turning around.

Most graphics API documentation and performance tuning guides recommend allocating resources you need the most as soon as possible, to ensure they get stored in the fastest storage available on the graphics card.

A 4096x4096 shadow map uses four bytes per pixel, so each one of them requires 64 megabytes of memory, and the game most needs multiple ones to do the distance cascading trick. Other shadow-casting light sources probably need a few maps too. Let's assume there's about three 4096x4096 maps worth of shadowmap buffers there (no, they're not all 4096x4096, but the total sum of pixels might be close). That's 192 megabytes of memory on shadow maps alone.

Then there's the framebuffer -- triple buffering and 4xAA @ 1920x1200, 8 bit per component RGBA (or ABGR) so again 4 bytes per pixel = 1920 * 1200 * 4 * 4 * 3 = 105 megabytes for just that. These don't absolutely need to be multisampled, but if you force AA through drivers it's probably going to happen.

The internal buffers the game uses for its HDR probably have 16-bit color components instead of the framebuffer's eight, so it's _8_ bytes per pixel. Need to multisample them too, no point in AA otherwise. There's at least one of them, maybe two. 141 megabytes in the latter case.

Oh, and a depth buffer. Got to have at least one of those. 4 bytes per depth sample, and we're still multisampling. 1920 * 1200 * 4 * 4 = 35 megabytes.

192+105+35+140 = 472 megabytes of video memory.

Yes, there's plenty of reason for this game to allocate lots of memory on startup.

Edit: brainfart corrected.

I just set 8xMSAA and its same 200 mb vram usage (high shadows) in main menu on fresh start. 500 with ultra shadows. So MSAA consume very little amount of ram.

Its a insane amount of vram need for shadow buffer, especially with 1 gb videocards. Not much remains for textures and meshes.

Skyrim's shadow buffer use obviously much more than 192 mb for 4096x4096 shadow maps. 500 mb vram consumption with 4096x4096 maps and just 200 mb with 2048x2048.

Then it's making more of them for whatever reason, but it still makes sense to allocate the most frequently needed (and most infrequently deallocated) things first, and it's not like you're going to run out of vram with the textures being what they are

Oh, and I forgot about multisampled depth buffers earlier.

My Radeon 5770 1gb videocard is running out of ram actually. Or how to explain weird stuttering bug then(jumping from 60 fps to 30 and back when even standing still)? Its totally disappeared, when I set shadows to high.

That's odd. I tried maxing out the game on my GTX 560 Ti by putting everything on Ultra, 8xAA, 16xAF, FXAA enabled and Nvidia's driver SSAO hacked on in Fallout 3 mode.

It ran fairly well, just got generally slow-ish in places like Whiterun, but didn't stutter. According to Nvidia Inspector the vram usage was at 83%. Ended up switching off the extra AA since the FPS dips were making the mouse responsiveness issue worse.

That's twice odd, because with ultra shadows fps dips doesn't appear in many places, outdoors as well. But with high shadows stuttering magically disappear everywhere.

Wouldn't be surprised at all if there were driver bugs -- seems like there was fairly little pre-launch work with the hardware makers and even Nvidia ended up rushing out a beta driver for this game.

The beta driver seems fairly stable at least.