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New001
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2,668 Posts
Discussion Starter #1
Recently I was helping to chose a laptop for a friends 12 yr old, with a price range of around AU$700. The primary purpose of the machine was to play minecraft.
My query isnt about buying a laptop, it's just what made me want to know the answer to the question here

While I was looking around at laptops of this price range, I came across the i5-6200U with Intel HD520 graphics and the GTX 920m.

The GTX 920m runs 2GB of DDR3 at a slightly lower core frequency than the turbo'd intel graphics.
The laptop has 4GB of DDR4, of which I guess around 2.5 - 3GB would be available to the intel graphics.
The 920m also has a narrower memory bus (128-bit vs 256-bit) and slower frequency memory.

After looking at some benchmark/reviews on these two graphics chips and Minecraft, it turned out that most people found that Minecraft performed far better / smoother / more consistent and high FPS on the integrated graphics HD 520 vs 920m.

I was thinking about why this might be and was hoping someone could fill in some missing info.

I reasoned that with a game as small as Minecraft, there is no issues with RAM availability. Because of this, the shared memory with the system is not a problem (eg, still 2.5GB free for minecraft to play with). The QPI interconnect between the CPU and system memory would be much faster than the link between the primary PCIe slot (holding the 920m) and the CPU and this would result in the better performance from the integrated graphics (given that the intel HD 520 and GTX 920m have almost the same sort of performance numbers when looking on GPU comparison sites).

If we were looking at a game such as GTA V, performance would be better on the 920m because the game would require the combination of both the system ram and the dedicated 2GB on the 920m and therefor would see more of a bottleneck with the integrated graphics and only the free system ram at its disposal.

Are my assumptions correct, or am I way off the mark in this rough understanding of what is going on here?
 

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New001
Joined
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2,668 Posts
Discussion Starter #2
no one?

edit: OK
I looked a bit further and found the i5-6200U has a qpi link speed of ~34GB/s and a dmi3.0 link of 3.5GB/s
so the link between CPU and memory is 10 times as fast as link between CPU and graphics.

Then for a game like minecraft which fits easily into shared ram, it will see a bottleneck having to communicate over the DMI link compared with the integrated graphics.

I'm hoping an electrical engineer or someone that knows this stuff on a deeper level can help with this understanding as it's quite interesting to me but i cant find conclusive evidence that says for a fact what is going on.
 
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