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2016 rMBP: AMD dGPU scaling is blurrier than Intel iGPU

M

m0dest

macrumors member
Original poster
Apr 16, 2010
36
52
The rMB and rMBP depend heavily on hardware scaling to be able to simulate higher resolutions. Even the default resolution is scaled. On the 15" rMBP, the system renders at 3360x2100 ("Looks like 1680x1050"), then the dGPU/iGPU downscales it to the LCD's native resolution of 2880x1800.

Since the first Retina MacBook Pro, Apple has done a great job here. The scaling algorithms were very sharp, preserving crisp text and lines. And, until this model, Apple pulled off an impressive feat: the same sharp downscaling algorithm was used by both the Intel graphics and the discrete GPU, so switching caused no visible changes to the user.

This is no longer true with the 2016 rMBP. The AMD dGPU uses a different, blurrier downscaling algorithm than to the Intel integrated graphics. As a result, the internal display becomes more blurry as soon as any app requires the discrete GPU... and then reverts after the app is finished with the discrete GPU.

To test this with your 2016 MacBook Pro:
  1. Disconnect any external displays (as these force discrete GPU).
  2. Quit all apps (as some apps may force the discrete GPU). Having a PDF in Preview for comparison is probably okay.
  3. Open the Displays prefpane. Set the display resolution to More Space ("Looks like 1920x1200").
  4. Open the Energy Saver prefpane.
  5. Uncheck "Automated graphics switching". This will force the discrete GPU. Notice that all text becomes blurrier. Check it again to compare the difference.
What do you see?

My configuration:
2016 MacBook Pro 15"
2.9 GHz Intel Core i7 (Intel HD Graphics 530)
Radeon Pro 460
 
Last edited:
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m0dest said:
T
The AMD dGPU uses a different, blurrier downscaling algorithm than to the Intel integrated graphics. As a result, the internal display becomes blurrier as soon as any app requires the discrete GPU...
Click to expand...

Sounds horrible, any chance you could take screenshots before / after and post them here?
 
m0dest said:
The rMB and rMBP depend heavily on hardware scaling to be able to simulate higher resolutions. Even the default resolution is scaled. On the 15" rMBP, the system renders at 3360x2100 ("Looks like 1680x1050"), then the dGPU/iGPU downscales it to the LCD's native resolution of 2880x1800.

Since the first Retina MacBook Pro, Apple has done a great job here. The scaling algorithms were very sharp, preserving crisp text and lines. And, until this model, Apple pulled off an impressive feat: the same sharp downscaling algorithm was used by both the Intel graphics and the discrete GPU, so switching caused no visible changes to the user.

This is no longer true with the 2016 rMBP. The AMD dGPU uses a different, blurrier downscaling algorithm than to the Intel integrated graphics. As a result, the internal display becomes blurrier as soon as any app requires the discrete GPU... and then reverts after the app is finished with the discrete GPU.

To test this with your 2016 MacBook Pro:
  1. Disconnect any external displays (as these force discrete GPU).
  2. Quit all apps (as some apps may force the discrete GPU). Having a PDF in Preview for comparison is probably okay.
  3. Open the Displays prefpane. Set the display resolution to More Space ("Looks like 1920x1200").
  4. Open the Energy Saver prefpane.
  5. Uncheck "Automated graphics switching". This will force the discrete GPU. Notice that all text becomes blurrier. Check it again to compare the difference.
What do you see?

My configuration:
2016 MacBook Pro 15"
2.9 GHz Intel Core i7 (Intel HD Graphics 530)
Radeon Pro 460
Click to expand...

Everytime I post in these forums about how disappointed with the 460 our company was, some Apple Zealot tries to cut my head off telling me I don't know what I'm talking about. We already sent our 13" and 15" back after testing, beacuse we where hard pressed to invest on a new build, new design, ports, new everything.. I wish we still had ours to test, we have tons of monitors here.. every flavor. That being said... Honestly it sounds like software. Since it is a new build, new drivers new GPU, Apple is still working out the kinks.. Their is nothing, from a technical standpoint, the 460 can't do that the Iris can. I imagine its just because the MacBook Retina, the MacBook 13" and the MacBook 15"(maybe?) are using the IRIS for the Retina onboard display, and the 460 driving the external doesn't have all the OS X possibilities in its drivers..
 
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Yes, please, screenshots. Also, file a bug report-- this is most probably a software issue that needs fixing.
 
Presumably screenshots won't work as they will save at the non downscaled res. You would need to take a photo of the screen.
 
I have absolutely seen different GPUs do better or worse scaling. Just... Not normally noticably so at this scale.

But we have one machine with a 450 and one with a 460, so I can check this out at some point.
 
DavidNZ said:
Presumably screenshots won't work as they will save at the non downscaled res. You would need to take a photo of the screen.
Click to expand...

Correct; screenshots would not work because they show the unscaled resolution.
Requires a good camera shot to catch the pixel differences. I'll give it a try when I get a chance.
 
m0dest said:
  1. Uncheck "Automated graphics switching". This will force the discrete GPU. Notice that all text becomes blurrier. Check it again to compare the difference.
What do you see?
Click to expand...

Yep, sure do. I can confirm this does occur (but I would never have noticed if I didn't read this).

My setup:
15" TB-RMBP 2016 (A1707)
2.7GHz Intel Core i7 (Intel HD Graphics 530)
Radeon Pro 460 (4GB-VRAM)
 
Haven't been able to reproduce this yet. Although charmingly I appear to now have a horizontal black line on my screen. Weirder still, it reflects movement from elsewhere on the screen, making it look more like a video memory corruption thing than dead pixels. Definitely wasn't there the other day.

Okay, staring really closely, basically, I can see a slight change in font rendering, but it's not obvious to me, and I wouldn't call one significantly better than the other.
 
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I see no difference at all....I have the exact same config as you

EDIT...closed Safari and now I see it...but don't care as it is so insignificant and I have Safari open all the time anyways so it won't make a difference...
 
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