RUM: K moznemu teoretickemu vlivu zpomaleni 0.5GB sektoru, za predpokladu, ze jsou mereni relevantni:
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Sure. But it leaves quite some uncertainty, since utilization was at max for only 2 points and rest was quite below.
But to add actual value, since only one person went to create my synthetic scenario to see possible impact (not regular one), I'll show some math.
GTX970 has official memory bandwidth of 224GB/s.
Nai's Bench shows 150GB/s for fast part & from 6 to 22GB/s for slow part. Normalizing this to:
224GB/s for fast & 21GB/s for slow address space.
Scenario 1: Big game uses 3.2GB, but per frame uses only 768MB (0.75GB)
- best case scenario: 0.75 / 224 = 0.00335 ~ max achievable fps = 298.67
- worst case scenario: 0.5 / 21 + 0.25 / 224 = 0.0249 ~ max achievable fps = 40.12
- Average scenario: 0.09375 / 21 + 0.65625 / 224 = 0.0074 ~ max achievable fps = 135
Scenario 2: very small game utilizing 0.75GB, but per frame using exactly 0.5GB (small arena game)
- best case: 0.5 / 224 = 0.002232 ~ max fps = 448
- worst case: 0.5 / 21 = 0.02381 ~ max fps = 42
- average case: 0.0625 / 21 + 0.4375 / 224 = 0.004929 ~ max fps = 203
Explanation for average case:
Click to show spoiler
And as you can see, since performance of games which utilize on their own 3.5GB of vram is already in range of 25 to 45 fps, impact of this slow part is minimal.
I believe nVidia did best thing they could by separating address spaces this way. Because otherwise there would be cases where perfectly fine running games end up with huge framerate drops. Imagine going from 120 to 40fps with no apparent visual effects going on screen, just by entering room full of slow textures.
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Takze i kdybychom do udajne pomaleho sektoru umistili framebuffer, fps nemuze klesnout pod 40fps.
Cimz bych debatu o hratelne hranici fps ucinne uzavrel :)