We’re already well acquainted with AMD’s Radeon HD 7870 and 7850 graphics cards. We studied them, and the Pitcairn graphics processors that dwell within them, about three weeks ago. In that initial encounter, we learned that these cards have all the makings of successors to the popular Radeon HD 6800 series: similar-sized GPUs and memory interfaces, with lower power requirements. The newcomers are quite a bit faster, too. Thanks to a new 28-nm chip fabrication process and a revised graphics architecture, dubbed GCN, they even outpace the old Radeon HD 6900 series cards, which are based on larger chips.
Unfortunately for bargain hunters, AMD has priced the Radeon HD 7850 and 7870 at $249 and $349, respectively, well above the $180-240 price range the 6800 series occupied when it arrived in October 2010. Whispers around the industry suggest the higher prices can be attributed the limited supply of 28-nm wafers coming from TSMC, the Taiwanese foundry that manufactures chips for AMD, Nvidia, and other firms like Qualcomm. Nvidia charges a pretty penny for its freshly released GeForce GTX 680, too, which has a smaller GPU and the same memory interface width as the GeForce GTX 560 Ti yet sells for twice as much.
In a nutshell, the 7800-series Radeons deliver only slightly better performance per dollar than the prior-gen Radeon HD 6900 cards, though they have the potential to be much cheaper. Not much of a consolation prize, I know.
The new Radeons therefore have to play up their other advantages in order to seduce prospective buyers. One of those advantages is a rather substantial amount of overclocking headroom. Our reference Radeon HD 7870, which came to us directly from AMD, had no trouble climbing from its stock 1000MHz clock speed all the way up to a blistering 1275MHz. We were able to overclock its memory from 1200MHz to 1375MHz, as well. Those settings yielded substantial performance gains without huge increases in power consumption.
Unsurprisingly, board makers have jumped on the opportunity to serve up customized, higher-clocked versions of the Radeon HD 7870 and Radeon HD 7850. (Such cards are sometimes referred to as “overclocked in the box,” but that’s a bit of a misnomer, since no overclocking actually takes place. The cards ship with the higher clocks and are fully supported by the manufacturer.) Today, we’re looking at a couple of hot-clocked cards, both hailing from XFX.
Behold, the XFX Double D HD 7870 Black Edition and Double D HD 7850 Black Edition:
Which one is the 7850, and which one is the 7870, you ask? Well, have a look at a couple more pictures, and see if you can guess:
Yes, the only identifiable difference is the writing on the top of the cards. The two products otherwise look identical, with the same board-and-cooler length (9.76″), the same number of six-pin PCI Express power connectors (two), and the same cluster of display outputs (dual DVI, dual mini DisplayPort, and a single HDMI port). Both cards also feature the same cooler, whose four copper heat pipes make direct contact with the GPU and spread out into an array of aluminum fins. The whole shindig is kept chilly by a pair of “dust-proof” fans. In this case, “dust-proof” means dust shouldn’t get inside the motor, not that you won’t have miniature dust bunnies collecting on the fan blades after a few months. XFX claims its cooler design enables lower temperatures and noise levels than the competition.
XFX uses a similar shroud on its Double D HD 7970 Black Edition, which performed exceptionally in our testing, but the underlying coolers are actually quite different. The 7970 features a vapor-chamber heatsink with a copper base and, from what we can tell, more aluminum fins. XFX’s Double D branding seems to refer to the presence of dual fans and not to a specific cooler design.
XFX touts the card’s other perks, such as solid-state capacitors, ferrite iron core chokes, and a circuit board containing two ounces of copper. And it offers lifetime warranty coverage, provided you register the cards on its website within 30 days of purchase; otherwise, the warranty drops to two years.
Those are the similarities. Now for the differences: the Double D HD 7870 Black Edition runs at 1050MHz, and its memory ticks away at 1250MHz for an effective transfer rate of 5000 MT/s. That’s a step above the GPU and memory speeds of the reference AMD card, which are 1000MHz and 1200MHz, respectively. The difference between the Double D HD 7850 Black Edition and the reference Radeon HD 7850 are greater: the Black Edition runs at 975MHz with a 1250MHz memory speed, while the AMD card is clocked at 860/1200MHz.
The 7870 and 7850 Black Edition otherwise have the same internal resources as their reference counterparts: 1280 ALUs and 80 texture units on the 7870, and 1024 ALUs backed by 64 texture units on the 7850. Both are complemented by 2GB of video RAM.
As you’d expect, those clock speed increases don’t come free of charge. XFX prices the 7850 Black Edition at $279, about 30 bucks above stock-clocked cards. The 7870 Black Edition will set you back a cool $389, which is equivalent to a $40 markup over vanilla models. XFX is asking a fair bit for speed increases that, based on what we’ve seen, may be easily attainable with cheaper offerings and a little manual tweaking. However, the XFX cards have fancy coolers and might have further overclocking headroom in store. Let’s have a look, shall we?
Our testing methods
As ever, we did our best to deliver clean benchmark numbers. Tests were run at least three times, and we reported the median results. Our test systems were configured like so:
|Processor||Intel Core i5-750|
|North bridge||Intel P55 Express|
|Memory size||4GB (2 DIMMs)|
|Memory type||Kingston HyperX KHX2133C9AD3X2K2/4GX
DDR3 SDRAM at 1333MHz
|Memory timings||9-9-9-24 1T|
|Chipset drivers||INF update 18.104.22.1685
Rapid Storage Technology 10.1.0.1008
|Audio||Integrated Via VT1828S
with 22.214.171.12400 drivers
|Hard drive||Western Digital Caviar Black 1TB
Samsung Spinpoint F1 HD103UJ 1TB SATA
|Power supply||Corsair HX750W 750W|
|OS||Windows 7 Ultimate x64 Edition
Service Pack 1
|Driver revision||GPU core
|Asus GeForce GTX 560 Ti DirectCU II||GeForce 295.73||830||1000||1024|
|Asus GeForce GTX 570 DirectCU II||GeForce 295.73||742||950||1280|
|Asus Radeon HD 6870 DirectCU||Catalyst 8.95.5-120224a||915||1050||1024|
|XFX Radeon HD 6950||Catalyst 8.95.5-120224a||830||1300||1024|
|Asus Radeon HD 6970 DirectCU II||Catalyst 8.95.5-120224a||890||1375||2048|
|Radeon HD 7850||Catalyst 8.95.5-120224a||860||1200||2048|
|Radeon HD 7870 GHz Edition||Catalyst 8.95.5-120224a||1000||1200||2048|
|XFX Double D HD 7870 Black Edition||Catalyst 8.95.5-120224a||1050||1250||2048|
|XFX Double D HD 7850 Black Edition||Catalyst 8.95.5-120224a||975||1250||2048|
Thanks to Asus, Corsair, Kingston, Intel, Samsung, and Western Digital for helping to outfit our test rigs with some of the finest hardware available. AMD, Nvidia, and the makers of the various products supplied the graphics cards for testing, as well.
Unless otherwise specified, image quality settings for the graphics cards were left at the control panel defaults. Vertical refresh sync (vsync) was disabled for all tests.
We used the following test applications:
Some further notes on our methods:
- We used the Fraps utility to record frame rates while playing a 90-second sequence from the game. Although capturing frame rates while playing isn’t precisely repeatable, we tried to make each run as similar as possible to all of the others. We tested each Fraps sequence five times per video card in order to counteract any variability. We’ve included frame-by-frame results from Fraps for each game, and in those plots, you’re seeing the results from a single, representative pass through the test sequence.
We measured total system power consumption at the wall socket using a P3 Kill A Watt digital power meter. The monitor was plugged into a separate outlet, so its power draw was not part of our measurement. The cards were plugged into a motherboard on an open test bench.
The idle measurements were taken at the Windows desktop with the Aero theme enabled. The cards were tested under load running Skyrim at its Ultra quality preset with FXAA enabled.
We measured noise levels on our test system, sitting on an open test bench, using a TES-52 digital sound level meter. The meter was held approximately 8″ from the test system at a height even with the top of the video card.
You can think of these noise level measurements much like our system power consumption tests, because the entire systems’ noise levels were measured. Of course, noise levels will vary greatly in the real world along with the acoustic properties of the PC enclosure used, whether the enclosure provides adequate cooling to avoid a card’s highest fan speeds, placement of the enclosure in the room, and a whole range of other variables. These results should give a reasonably good picture of comparative fan noise, though.
- We used GPU-Z to log GPU temperatures during our load testing.
The tests and methods we employ are generally publicly available and reproducible. If you have questions about our methods, hit our forums to talk with us about them.
Batman: Arkham City
To warm up this latest batch of Radeons, we grappled and glided our way around Gotham, occasionally touching down to mingle with the inhabitants.
We tested at a 1080p resolution with DirectX 11 effects enabled, normal tessellation, high FXAA antialiasing, and everything else cranked up. Those settings seemed to yield the best compromise of image quality and smoothness on the 7870.
We should preface the results with a little primer on our testing methodology. Along with measuring average frames per second, we delve inside the second to look at frame rendering times. Studying the time taken to render each frame gives us a better sense of playability, because it highlights issues like skipping, stuttering, and microstuttering that can all occur—and be felt by the player—within the span of one second. Charting frame times shows these issues clear as day, while charting average frames per second obscures them.
For example, imagine one hypothetical second of gameplay. Almost all frames in that second are rendered in 16.7 ms, but the game briefly hangs, taking a disproportionate 100 ms to produce one frame and then catching up by cranking out the next frame in 5 ms—not an uncommon scenario. You’re going to feel the game hitch, but the FPS counter will only report a dip from 60 to 56 FPS, which would suggest a negligible, imperceptible change. Looking inside the second helps us detect such skips, as well as other issues that conventional frame rate data measured in FPS tends to obscure.
We’re going to start by charting frame times over the totality of a representative run for each card. That should give us an at-a-glance impression of overall playability, warts and all. (Note that, since we’re looking at frame latencies, plots sitting lower on the Y axis indicate quicker cards.)
We can slice and dice our raw frame-time data in three ways, as you’re about to see. By the way, we should caution that none of the graphs below can be construed as self-contained scoreboards; instead, they each show a different facet of the cards’ performance, and they should be viewed as a whole along with the raw frame-time plots above.
Our first graph shows average frames per second. Though this metric doesn’t account for irregularities in frame latencies, it does give us some sense of typical performance.
In our second graph, we’re demarcating the threshold below which 99% of frames are rendered. The lower the threshold, the more fluid the game. This metric offers a sense of overall frame latency, but it filters out fringe cases.
Our last graph tells us how long each card worked on frames that took longer than 50 ms to render. Ideally, the result should be “0” for every card. That’s because the illusion of smooth motion is likely to begin breaking down once frame latencies rise into that territory. (For reference, 50 ms frame times would work out to a 20 FPS average.) In a nutshell, this metric tells us how badly each card skips during gameplay, if it does at all.
Well, our XFX cards are off to a nice start. The 7870 Black may not be a great deal faster than its reference counterpart, but the 7850 Black edges out the vanilla 7850 by a big margin—especially in our “time spent beyond 50 ms” metric. Lower scores there indicate fewer latency spikes and thus more fluid overall gameplay.
We tested Battlefield 3 by playing through the start of the Kaffarov mission, right after the player lands. Our 90-second runs involved walking through the woods and getting into a firefight with a group of hostiles, who fired and lobbed grenades at us.
The game was run at its highest detail preset, Ultra, which couples MSAA and FXAA antialiasing as well as snazzy DX11 effects and tessellation.
Things get a little strange here. The 7870 Black continues to do well, but the 7850 Black actually falls slightly behind the reference 7850. The difference amounts to less than half a frame per second, so for all intents and purposes, we can say the two cards perform identically. But that doesn’t make sense—the Black Edition is clocked 115MHz above the reference card, and its memory is 50MHz faster.
We re-tested, tweaked PowerTune settings, checked for overheating, and poked and prodded trying to find the source of the problem, but nothing seemed out of order. We even tried clocking the XFX card at the same speeds as the vanilla 7850, and performance declined further. Suspecting a memory latency difference, we called XFX for comment. The company said that, save for clock speeds, the Black and reference cards should be identical at the firmware level. Any straightforward explanations for the performance discrepancy were suddenly ruled out.
Later that day, the company got back to us again. They’d spoken to another reviewer, and guess what? The 7850 Black’s higher-than-normal clock speeds didn’t seem to “do anything” in some cases, he said.
In other words, we may be looking at a bizarre, presently unresolved bug with this particular card. Maybe the bug lies in the drivers, or maybe it’s some hidden firmware kink. The question is, does it rear its head in other games?
We tested Crytek’s latest shooter by running and gunned through the game’s rendition of Battery Park, sticking to the same path through the level to avoid drastic differences between samples.
The game was set to run at a 1920×1080 resolution with the “Extreme” detail preset. Both the DX11 “ultra upgrade” and high-res texture pack were installed, and both were enabled.
The 7870 Black tops the charts yet again, but the 7850 Black is in a similar position as in Battlefield 3: its substantially higher clock speeds don’t seem to help very much, if at all.
The Elder Scrolls V: Skyrim
Our Skyrim run involved running around the town of Whiterun, starting from the city gates, all the way up to Dragonsreach, and then back down again.
Like BF3 and Bulletstorm, Skyrim‘s detail settings were maxed out. We selected the Ultra preset, which includes 8X MSAA, and then we enabled FXAA in the advanced options for good measure.
The 7850 Black makes a comeback in Skyrim, where it nips at the Radeon HD 7870’s heels (and actually pulls off slightly lower 99th-percentile frame times). That leaves us with two games where the card behaves as it should, and two games where it’s no better than the reference model. Hmm.
The XFX cards’ higher clock speeds don’t impact idle power consumption. Only under load do they draw more power, and not by all that much. The Radeon HD 7870 Black still consumes less power than the old Radeon HD 6870.
Noise levels and GPU temperatures
We weren’t terribly thrilled with the coolers on the reference 7800-series Radeons, which are a little loud under load. The XFX cards take care of that problem rather nicely—they’re wonderfully quiet under load.
Unfortunately, the lower noise levels come at a cost: higher temperatures. The 7870 Black runs a whopping 15°C hotter than its reference cousin.
Superclocked as they might be, these XFX cards surely have some headroom left under their hoods. Rather than bore you with a verbose description of our overclocking attempts, I’m going to paste my notes verbatim. I overclocked using AMD’s Catalyst Control Center application, tweaked voltages with MSI’s Afterburner utility, and tested stability with Kombustor, another MSI app. (XFX doesn’t provide its own overclocking tools for these Radeons.)
Ready? Here’s how the 7850 Black Edition fared:
1000MHz — OK after 5 min burn-in
1025MHz — OK after 5 min burn-in
1050MHz (max) — OK after 5 min burn-in
1250MHz — 6506 kombustor — stock
1350MHz — 6925 kombustor — ok after 5-min burn-in
1400MHz — 6690 kombustor — reverted
1375MHz — 7072 kombustor — ok after 5-min burn-in
Overvolt: no go. afterburner hard-locks system
Max: 1050/1350 (vs 975/1250 stock).
Temperature around 75C during kombustor burn-in.
And here are my results with the 7870 Black Edition:
1200MHz — OK after 5 min burn-in
1300MHz — crash
1275MHz — crash
1250MHz — display coruption
1225MHz — crash
1250MHz — 6721 kombustor — stock
1350MHz — 7194 kombustor — OK after 5 min burn-in
1400MHz — 6959 kombustor — reverted
1375MHz — 7354 kombustor — OK after 5 min burn-in
Max at stock voltage: 1200/1375 (vs 1050/1250 stock).
Temperature around 87C during kombustor burn-in.
1300/1375MHz — 1.300v — crash
1275/1375MHz — 1.300v — overheat
1250/1375MHz — 1.300v — overheat (over 105C in kombustor)
These results are a little disappointing. Neither card seemed to tolerate overvolting; the 7850 Black froze when we launched MSI Afterburner to tweak voltages, and the 7870 Black overheated quickly, with its GPU getting hot enough to boil water and subsequently shutting down. We’d excuse that behavior if the settings we tried had been particularly daring, but our reference Radeon HD 7870 handled itself just fine at 1250MHz with 1375MHz memory and 1.30V.
Clearly, the AMD cooler is better equipped to handle high overclocks than its XFX Double D counterpart. Our findings suggest the difference may hinge on the amount of metal under those cooling shrouds. Fan control didn’t appear to be an issue—the XFX 7870 ramped up its two fans without fault as temperatures climbed, hitting a speed of 73% at 95°C and 100% at 101°C. After that point, though, the card started throttling itself to stay cool, even with the fans pegged.
Happily, when overclocked by hand, the 7850 Black emerged out of its torpor in Battlefield 3. It outran the reference-clocked 7850 handily, nestling itself not far below the Radeon HD 7870. Load power consumption only increased by about four watts, as well, which is negligible.
As for the 7870 Black, even though its overclock didn’t match that of our reference card, it still put on a good show. The temperature we measured in our Kombustor burn-in (87°C) makes us a little wary of applying the same overclock in a cramped PC build, though. Honestly, if you’re going to overclock a 7870 at all, we’d recommend getting one with a more capable cooler than what XFX provides.
Up for a couple of value scatter plots before we call it a day? As is our custom, we’ve laid our performance results (based on the overall average performance from our game tests) along the Y axis and the cards’ pricing (obtained from Newegg, when possible, or from the manufacturer’s suggested e-tail price) along the X axis. The most desirable offerings will be the ones closest to the top left of the plot. The least desirable ones will be at the bottom right.
We can also compile a value scatter plot out of our 99th percentile frame time data. For consistency’s sake, we’ve converted the frame times to frame rates, so desirable offerings are still at the top left.
No doubt about it, XFX demands a sizable premium for somewhat modest performance increases—perhaps not in the case of the 7850 Black, which underperformed due to a potential bug that’s probably temporary, but definitely for the 7870 Black. $40 is a lot to pay for such a small jump over stock performance, and the fact that the card doesn’t overclock as well as the reference model makes it even harder to recommend.
The XFX 7870 does have a couple of redeeming features. Its cooler, though ill-equipped for high overclocks, is much quieter than AMD’s design at stock speeds. That might sweeten the deal for folks who care about noise levels—although we should point out that other cards with large, dual- or triple-fan coolers can be had for as little as $360. We haven’t tested those, however. Also, there’s the lifetime warranty to consider. XFX is one of very few vendors to offer that particular perk.
Nevertheless, considering our past experience with XFX’s Black Editions, I must confess to being a tad disappointed by these two cards. Even if you don’t mind paying a premium, there are deal breakers in both cases: the 7870 cooler’s inadequacy when it comes to overclocking, and the 7850’s weird performance issues, which negate the benefits of its higher clock speeds in Battlefield 3, Crysis 2, and perhaps other titles.
If XFX can resolve the latter, the 7850 Black could be a tantalizing choice. We’ve seen in Arkham City and Skyrim that it comes awfully close to the stock Radeon HD 7870—and we’ve also seen that it overclocks effortlessly at the stock voltage, without its power consumption increasing a whole lot. $279 may not be cheap for a 7850, but it’s definitely not bad for a card that can come so close to the $349 Radeon HD 7870. If it weren’t for the (admittedly minor) performance issue we encountered, the 7850 Black would be an Editor’s Choice for sure.