Value and Conclusion

It took NVIDIA a few months, but they've now achieved parity with AMD's Radeon Smart Access Memory feature. Instead of inventing a snazzy-sounding l33t pro gamer name, they simply refer to it as "Resizable BAR," which is the technologically correct term. While AMD enabled Resizable BAR across the board, for all titles, NVIDIA chose a more fine-grained approach—Resizable BAR is only activated for specific games after NVIDIA has tested them.

Just to clarify on this point a bit, AMD made it clear that best gains from Resizable BAR require game-specific optimizations. So both companies optimize for games, the most popular first. NVIDIA is just more cautious, at the risk of missing out on gains for games that are not on their radar for whatever reason (too old, too new, or unpopular). I can imagine that future NVIDIA drivers will give you a driver control panel option that more aggressively enables Resizable BAR for more games, fingers crossed.

So far, NVIDIA has been very transparent about the list of games that have Resizable BAR support. At this time, there are 17 games: Assassin's Creed Valhalla, Battlefield V, Borderlands 3, Control, Cyberpunk 2077, Death Stranding, DIRT 5, F1 2020, Forza Horizon 4, Gears 5, Godfall, Hitman 2, Hitman 3, Horizon Zero Dawn, Metro Exodus, Red Dead Redemption 2, and Watch Dogs Legion. No doubt this list will get longer, pushed forward by NVIDIA's excellent engineering team and developer relations.

Out of our 22 game test suite, that's 12 titles, which is pretty decent. The gains vary wildly, though—around 20% (!!) in Gears 5 and almost nothing in other titles. On average, we saw a 2–4% performance improvement from Resizable BAR when counting titles with BAR support in the driver. Now, we of course have 10 more titles in our test suite without BAR support, which drags down the overall average, but I feel that looking at "BAR-only" games is the better approach since almost every title will benefit from Resizable BAR, it's just a matter of game support. While "a few percent" doesn't sound like much, it's free extra performance for a minimal investment and no loss in image quality. I wish I had insight into how many man-hours GPU makers spend on BAR support vs. traditional driver game optimizations.

Not all is green in the land of BAR. In our Watch Dogs Legions testing—a title that has NVIDIA's BAR blessings—I found a performance regression at 1080p. Once Resizable BAR is enabled, FPS rates are limited to around 80 FPS no matter the hardware. I repeatedly tested this with the same result. There's also some chatter online about various stutter issues with NVIDIA's FPS limiter, or monitoring software. Considering we're on NVIDIA's first driver, this is not a big deal, they'll get this fixed in no time. I am surprised we have to dig up the required VBIOS update on board partner sites and trust that their updater does the right thing all the time. Hint: It does not, there are quite a few reports about failed flashes. NVIDIA, with their tight grip on partners, could have certainly devised a centralized solution provided by NVIDIA that verifies and distributes the BIOS updates. AMD just got lucky this time around because their RDNA 2 cards were developed with PCIe Resizable BAR support in mind, which meant it didn't have to be added at a later time (remember RX 5600 XT BIOS updates?).

Update 7:20 pm CET:
Added a page with frametime charts

Update 7:30 pm CET:
You can use NVIDIA Profile Inspector to modify Resizable BAR game support settings. Credit goes to @chrcoluk.

• In NVIDIA Profile Inspector, in the toolbar, enable "Show unknown setting from NVIDIA Predefined Profiles"
• Now if you browse any game in NVIDIA Inspector in the Unknown flags at bottom, look for the following lines: 0x000F00BA, 0x000F00BB and 0x000F00FF.
• For games that are whitelisted these flags will probably be already enabled, for other games the value will be 0x00000000. You can flip it to 0x00000001. The third flag 0x000F00FF needs to be set to 0x0000000040000000