The Robservatory

Robservations on everything…


Two year old crushes the new (video card) kid on the block…

My 2019 iMac has the new AMD Pro Vega 48 video card, the fastest video card Apple has offered in a (non-Pro) iMac. But just how fast is it? I'll have more to say about it in an upcoming "games shootout" with my 2014 iMac, but I was also curious as to how (badly) it might compare to the video card—an NVIDIA GeForce GTX 1080—in my 2017 Frankenmac.

While I'd love to be able to compare the performance under macOS on Frankenmac, that's not possible as I uninstalled it a while back—I'd been unable to update to Mojave due to a lack of NVIDIA drivers for Mojave. (Which is related to all of this, in that you cannot use an NVIDIA card—with acceleration—in Mojave, even in an external GPU box, because it seems Apple and NVIDIA aren't on speaking terms right now.)

However, because a number of the benchmark apps I used in my 2019 iMac vs 2014 iMac—Part One comparison test also run on Windows, I was able to do some head-to-head testing, even if the difference in the OS adds a layer of unknown to the results.

Going in, I was pretty sure I knew what the results would show: The Windows PC was going to crush the iMac in anything graphically related, but lose in the CPU tests. While the AMD card is a big step up from previous-generation iMacs, it's nowhere near bleeding edge—it's more like "minor scrape" edge—in the Windows world.

Anyway, I ran a bunch of tests, and the results were pretty much as I expected…

Benchmark Task 2019 iMac Win 10 PC New iMac is
Geekbench 4 CPU single core 6,331 5,358 +18%
CPU multi core 33,449 18,411 +82%
Compute OpenCL 141,327 187,407 -25%
GpuTest FurMark 6,720 / 112fps 9,207 / 153fps -27%
TessMark X64 15,535 / 235fps 27,055 / 451fps -43%
Pixmark Volplosion 5,186 / 86fps 8,591 / 143fps -40%
Plot3D 42,575 / 709fps 158,374 / 2,640fps -73%
Cinebench R15 OpenGL 166.0 120.8 +37%
R15 CPU 1,682 866 +94%
R20 CPU 4,132 2,135 +94%
Heaven - OpenGL FPS range 20.4 – 233.6 13.9 - 390.0 --
Average FPS 137.4 216.7 -37%
Score 3,461 5,459 -37%
Valley - OpenGL FPS range 43.1 – 185.2 16.4 - 241.2 --
Average FPS 112.5 147.6 -24%
Score 4,707 6,176 -24%

First up, it's not surprising that the CPU tests favored the iMac, as it has a brand-new eight core CPU, and the Windows PC has an older Core i7 with four cores. But in every graphical test—except for Cinebench R15 OpenGL—the GeForce card was notably faster than the AMD—sometimes embarassingly faster.

So while the AMD card is the best Apple's offered in a (non-Pro) iMac, it's still a long way from the competition. My NVIDIA GTX 1080 is roughly two years old, and yet it simply destroyed the 2019 AMD card. I so wish Apple would patch things up with NVIDIA and offer some truly leading-edge video cards for their desktop Macs—or at least the ability to install them in an external GPU box.

As an aside, I ran the above tests using OpenGL, so as to be most directly comparable to the iMac's results. But Windows machines have another graphics interface available, DirectX. Here's how the Heaven benchmark compares with itself in Windows, run once in OpenGL and once in DirectX 11:

Benchmark Task OpenGL DirectX DirectX is
Heaven FPS range 13.9 – 390.0 9.6 - 432.9 --
Average FPS 216.7 238.7 +9%
Score 5,459 6,013 +9%

Using DirectX, the NVIDIA card holds an even larger advantage over the AMD.

So why'd I spring for the costly video card upgrade, if I knew going in it wouldn't really be top of the world performance? Because it was the fastest card available in the new iMac, and I tend to keep my iMacs for a number of years—so I try to spec the most powerful machine that'll fit in my budget, knowing it'll have to last for a number of years.

In addition, the comparison to an NVIDIA card in Windows isn't really relevant—if I wanted to use Windows all day, I wouldn't have a job that requires me to use a Mac. But I still enjoy working on my Mac, and playing the occasional game. And for that, the only comparison that matters to me is the new card versus the card in the 2014 iMac that it's replacing. I'll have more on that comparison in my games (and iMovie) comparison, coming soonish.

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