Soon after the launch of the 15-inch Retina MacBook Pro in June, we pointed to an analysis by AnandTech showing how the need to drive a massive number of pixels taxed the graphics capabilities of the machine to the point where it struggled to hit 20 frames per second while scrolling on resource-intensive web pages such as Facebook news feeds.
AnandTech now follows up with a new report based on a thread in our forums showing that the latest builds of WebKit, the open source browser engine upon which Safari is based, demonstrate dramatically improved frame rates during scrolling.
I grabbed a build (r135516 - it's no longer the latest build but I assume the later builds also contain the fix) and tried it out on the 13-inch rMBP. Scrolling down my Facebook news feed ended up being one of the best showcases for poor scrolling performance on the rMBPs, so that's obviously the first test I ran. As always I used Quartz Debug to measure UI frame rate.
The results show frame rates of around 20 frames per second (fps) under the standard Safari 6.0.2, but jump to nearly 50 fps when using nightly build r135516 of WebKit.

Frame rates approaching 50 fps when scrolling in WebKit nightly build r135515
AnandTech hasn't been able to determine exactly what code changes were made to enable the significant boost to scrolling performance on Retina MacBook Pro models, and it is unclear exactly when those changes will be incorporated into Safari itself, but it certainly seems that a solution is on its way.














Top Rated Comments
Everything is in constant motion.
That was ages ago. Today's webkit is a much larger beast than that old KHTML. Go ask Dave Hyatt how much work he's put into Webkit as an Apple employee.
To say Apple hasn't make a significant investment in Webkit is to be either ignorant or foolish or both.
It's a shame so many "trusted" review sites (including The Verge) dinged the rMBP and blamed the hardware.... for what is clearly a software problem.
And what I've been saying all along is quite correct, the problem is not the pixel pushing ability of the GPU. Pixel fill rates, look them up. Again, if you can't understand that a 4 year old GPU, the 9400m, could power a 30" ACD and that we're now in 2012, 4 years later, with GPUs 3 generations newer, I don't know how to explain it to you.
The 9400m could push 2.32 GP/s. Again, 4 years ago. 2880x1800 at 60 fps is roughly 311 MP/s. Are you getting this ? Even if what you say is true and HiDPI was so horridly optimized as you claim (which it isn't), that's still only half of the pixel fill rate of a now 4 year old Integrated GPU.
Anyway, I own a rMBP 15" and I've hardly met any "lag" whatsoever. I guess some people are just too sensitive. Thank god Apple knows it's a software issue and is fixing it for those people.
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The hardware is capable. You just don't understand GPU hardware or HiDPI to make such claims. Anand has always been full of it.