It’s been an exciting couple of weeks in the short life of the Radeon RX 480. AMD’s new graphics card is the first to use the next-generation Polaris 10 GPU, hot off the fabs. Unfortunately, not all of the excitement has been positive. Shortly after launch, the good people over at Tom’s Hardware and PC Perspective did some deep-diving on the new card’s power draw. The sites found that the card exceeded the specification for amperage drawn from the PCIe slot. This news ended up being a big concern for some potential RX 480 buyers.
In response, AMD released a statement saying that it didn’t think the 480’s excessive power draw was a threat to motherboards or other components in a system. Nevertheless, the company pushed out a new driver—Radeon Software 16.7.1—that re-balanced the board’s power draw, allowing it to pull more power from the PCIe 6-pin connector rather than the PCIe slot. The company also included a new option in the updated driver that would prevent the card from drawing quite as much juice in total for users who were particularly concerned about their systems. This “Compatibility Mode” can be toggled on and off in the Radeon Settings software, and it simply lowers the board’s power target. AMD is shipping the driver with this feature turned off by default.
Of course, making such low-level tweaks to the way the Radeon RX 480 works raised questions about how the card will perform post-update. Now that we’ve had some time with the new drivers and the new compatibility mode option we can give a clearer picture of the effect of this driver update on the games we tested. In the interest of time, we didn’t run our whole suite of benchmarks again. For the games that we did retest, we used the same set of settings and procedures that we used in our primary RX 480 review. We chose two games—Grand Theft Auto V and Crysis 3—to put back through the wringer, since they were both fairly playable at our test settings.
Crysis 3 revisited
We’ll start with Crysis 3 today, since it’s both a performance test and the benchmark we use to generate our power-use numbers. Crysis 3 is also a potentially interesting test because it’s an older game that AMD isn’t likely to have released any specific optimizations for. As we noted, we used the same graphics settings, the same benchmark run, and the same processing methods as we did in our full RX 480 review. We compared the results from our initial test
Our average FPS numbers look good. No news here. Most importantly, there’s barely any change in performance between the release driver for the card and the Radeon Software 16.7.1 update. While the new driver does appear to increase performance slightly, these are averages of hand-run benchmarks, so the results are probably well within any margin of error. As always, we don’t put all that much stock in pure-FPS measures since they don’t show the whole picture of graphics performance.
Our frame-time graphs are a bit crowded, but they basically tell us the tale we want to see. Performance between the release driver and the 16.7.1 update is largely the same. Turning on Compatibility Mode does cause our card to display a couple large spikes that could affect perceived smoothness, but that’s unsurprising since we’re probably reducing its power budget—and, hence, performance—somewhat.
These “time spent beyond X” graphs are measures of “badness”—the amount of time that a card was displaying animation that may have been less than fluid, or at least less than perfect, during our test. If frames are taking longer than 33.3ms to render, the frame rate will drop below 30 FPS. In those cases, we expect to have some judder and other ugliness with vsync enabled on a 60-Hz monitor.
The new driver performs admirably here, although we still see a small increase in the amount of time spent beyond both 16.7 and 8.3ms. The compatibility driver fares a bit worse, with an almost doubling of the time spent beyond the key 16.7ms. This isn’t surprising, given the lower power use, and it also does a good job of demonstrating exactly how sensitive these frame-time measurements are.
Grand Theft Auto V revisited
We also re-ran our Grand Theft Auto V tests with the same settings, the same benchmark run, and the same processing as our initial RX 480 review. The charts below are once again made up data from the new 16.7.1 driver, both with compatibility on and off, as well as the RX 480 performance from the release review. Grand Theft Auto V received specific attention from AMD in the new driver to reduce “minor stuttering,” so we’ll be looking to see whether the card delivers on that point.
The frame time chart itself is crowded, but that’s probably a good thing. The Radeon RX 480 already did well by this measure with GTA V, and the fact that the three data plots mostly overlap one another indicates that there aren’t any major changes in smoothness from our initial review.
It’s not really a surprise that the RX 480 with the new driver outperformed the RX 480 with the old driver in raw FPS, since the game received specific optimizations in this update. It’s also nice to see that that the power changes of compatibility mode balance out with the improvements in the new driver. With Compatibility Mode off, the RX 480 gets a 7% boost from this update.
The 99th-percentile frame time of the RX 480 also improves in this game. The card is just a hair off delivering 99% of its frames within 16.7 ms, so gamers can expect a mostly smooth experience from this update. That’s not to say the RX 480 performed badly with GTA V in the first place, but installing the 16.7.1 update makes it just that little bit better.
In keeping with our measured 99th-percentile frame time result, the 16.7.1 drivers shave the time spent beyond 16.7 ms way down compared to the release driver. Whether in Compatibility Mode or in regular operation, the RX 480 spends little time beyond that critical threshold, and it even beats the GeForce GTX 970 (although it’s worth noting that card has also had a couple driver updates since our initial tests). That’s a result AMD’s driver team should be proud of.
What about that power issue?
While it’s good to see performance remain mostly unchanged with this driver release, the major question is whether AMD actually fixed the bus power draw issue that prompted so much outrage to begin with. The purpose of this driver update wasn’t to make the card draw less power overall, but to improve the balance of power use between the PCIe 6-pin connector and the PCIe slot. Unfortunately, with our current power-testing setup we don’t have the granularity required to detect a power use change at the PCIe bus, and measuring system power draw doesn’t tell the whole story.
Tom’s Hardware and PC Perspective have both released updated power numbers with the new driver, and both sites report that the new update lets the card draw less power from the PCIe slot and more from the beefier six-pin PCIe connector direct from the PSU. With the new driver installed, and without compatibility mode enabled, PC Perspective found that the RX 480 draws about 6% more power from the PCIe slot than the standard would allow, as opposed to about 20% more with the release driver. While that number is still out of spec, it’s likely well within the capacity of any well-built motherboard to tolerate.
With the tools at hand, we discovered that turning on compatibility mode resulted in a roughly 5W drop in the power use on our test rig. That might not sound like a whole lot in the context of the whole system, but it’s a fairly big deal from a board-power perspective. Considering the fairly minor performance hit, it might be worth it to users who are particularly worried about whether their power supplies or motherboards are up to the task of running an RX 480.
All told, AMD’s update looks like it mostly resolves what could have been a sticky situation for the Radeon RX 480 reference card. The company appears to have successfully rebalanced the Radeon RX 480’s power draw from the PCIe slot to the six-pin auxiliary power connector without negatively impacting performance. The “compatibility mode” switch should offer an extra margin of safety for owners of systems who are concerned about the card’s impact on their systems, at the cost of a tiny bit of performance. If you’re OK with the reference blower design, the RX 480 once again looks like the $200-$240 card to beat for now.