Conclusion

Finally! Intel is letting us publish our performance results for their new Arc A Series graphics cards. We have three reviews for you today: Intel Arc A770, Intel Arc A750, and Arc A770 Performance with PCI-Express 3.0 and/or Resizable Bar Disabled (this article).

This has been an interesting article to write, as not only are testing the performance impact of Resizable BAR being disabled—something Intel is quite vocal about not doing; but also the impact of running it in PCIe Gen 3 mode. and permutations thereof (PCIe Gen 3 with and without R-BAR, and PCIe Gen 4 with and without R-BAR). Let's answer the easier question first, on just how much performance you stand to lose with PCIe Gen 3: None at all! With Resizable-BAR being enabled, PCIe Gen 3 inflicts barely a 0-2% performance penalty when averaged across all games. So those of you with 10th Gen Core or Ryzen 5000G APUs, rejoice, your PCIe Gen 3 bus still has some fight left in it, and 128 Gbps or 16 GB/s per direction bandwidth was always going to be sufficient for a performance-segment GPU like the A770—it certainly is for the RTX 3060, but affects performance of the RX 6600 XT (as tested in an older article), because of AMD's decision to narrow the PCIe bus to x8 (so PCIe Gen 3 x8 would start imposing performance costs).

You really need resizable-BAR for the Arc A770 to perform as advertised. The card is simply unusable without it, and Intel said as much throughout the marketing events leading up to this launch. With Resizable-BAR disabled, performance drops like a rock down to just 77% of the performance you get with it enabled at 1080p, and just 76% at 1440p—nearly a quarter of the performance lost. But that's averaged across all game tests, and presents an incomplete picture.

You also need to pay attention to the individual game tests to see the magnitude of unplayability in some games, such as Guardians of the Galaxy, which is a huge stutter-fest without Resizable-BAR. Quite a few of the games that tended to offer performance bonuses with R-BAR enabled on NVIDIA or AMD GPUs; actually see the biggest losses in performance with R-BAR disabled on the A770—these are the games that are doing something in their engine that makes them benefit a lot from R-BAR, and Intel's memory management gets wrecked without it. There really are no games worth pointing out where the lack of R-BAR makes minimal impact on performance. Every title suffers.

Intel is probably working to improve performance of R-BAR disabled/unavailable machines through driver updates, but even these could only slightly narrow the gap, because the limitation is due to the GPU's underlying architecture. The Arc "Alchemist" family was built keeping in mind that PCs with R-BAR have been available for the past four years at least; and the company exerts enough influence over its notebook and desktop OEMs to get them to enable it; so it's not unreasonable completely ignoring optimizing the architecture for machines without R-BAR, to free up valuable engineering resources for more critical parts of the GPU project.

But does Intel deserve flack for this? Not really. It's pretty transparent that these cards need R-BAR to perform as advertised—the cards do end up competitive with the RTX 3060, so you're getting what Intel promised. You also need to cut Intel some slack for going from a company that made boring IGPs to a GPU that's as fast as the RTX 2080 "Turing," while building nearly everything from scratch. While NVIDIA and AMD made the transition from AGP to PCIe, optimizing their memory architectures, Intel's GPUs were designed in a post-AGP, era where GPUs can have as much memory as they want. Optimizing for machines without R-BAR may be excused. So if you have R-BAR, enable it. If you don't have it, or can't have it for whatever reason (MBR boot drive, need CSM, etc.,), "just go get a 3060," as Intel puts it.