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AMD Radeon HD 7790 Review

SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
In a year which promises to be a slow one for new graphics cards, the HD 7790 is a breath of fresh air, even though it doesn’t target the enthusiast demographic. At $149 this is very much a product which aims to close a perceived gap in AMD’s lineup in more affordable price points. More importantly, it is supposed to introduce optimal performance levels at 1080P, today’s most-used resolution.

With their HD 7850 2GB retailing for about $199 and the lowly HD 7770 GHz Edition going for $119, AMD desperately needed a bridge solution between these two popular, yet miles apart cards. That’s where the HD 7790 comes in. It is primarily being introduced as a way to finally challenge GTX 650 Ti’s command of the $150 to $175 price point. However, considering NVIDIA’s card has been around for the better part of 6 months now, it will take one hell of an effort in order to weed out such a heavily entrenched competitor.


At the heart of AMD’s HD 7790 lies the 2.08 billion transistor Bonaire core which, like its predecessors, uses TSMC’s 28nm manufacturing process. Rather than using a warmed-over Pitcairn design, this one utilizes brand new silicon and incorporates a number of minor revisions to the typical Graphics Core Next architecture in order to increase overall efficiency. However, make no mistake about it: Bonaire is still a GCN-based ASIC within the HD 7000-series so don’t expect any over-the-top performance increases here.

Crammed onto this tiny 160mm² die is a pair of Geometry and asynchronous Compute Engines, a notable improvement over the single engine used within Cape Verde and more in-line with the layouts of higher-end Pitcairn and Tahiti cores. This allows the HD 7790 to process two primitives per clock and results in better tessellation performance and enhanced data throughput. It will also benefit DirectCompute performance, which has become quite important with the advent of compute-accelerated global illumination, AMD’s TressFX within Tomb Raider and even Far Cry 3’s enhanced HDAO.

The Bonaire core’s 14 Compute Units each have the typical 64 cores totaling 896 Stream Processors along with 56 Texture Units and 16 ROPs. This means the HD 7790’s pixel fillrate remains at 16 GP/s, identical to what the HD 7770 GHz can achieve but the texture fillrate gets a significant 40% boost to 56 GT/s.


Looking at AMD’s current lineup, it becomes evident that the yawning chasm between the HD 7850 and HD 7770 Ghz is finally being filled with a worthwhile product. The HD 7790 has nestled perfectly into its position but there will be some disappointment that it hasn’t come equipped with a 2GB frame buffer. Supposedly, some board partners will be introducing 2GB SKUs but no one expects those products to perform all that much better at 1080P.

The feature set of this new card has also been significantly expanded. It comes with native support for both Crossfire and Eyefinity, two items which NVIDIA cards in this price range currently don’t include.

AMD has also revealed some sad news: the venerable HD 7850 1GB is no longer being produced due to the GDDR5 memory modules it uses being discontinued. Its absence may be felt since it was a perfect gateway product for high performance at a low price point but the HD 7790 should take over much of the slack.


Another major change over previous designs in the mid to low end markets is the incorporation of memory controllers which support 6 Gbps GDDR5 modules. While the actual in-game performance increase may not be all that significant, a 10% bump in framerates certainly isn’t anything to thumb your nose at either. The inclusion of these modules on a lower end card also points to how quickly the price of GDDR5 is dropping and it should only be a matter of time until it completely supplants GDDR3 throughout AMD’s lineup.


One of Bonaire’s main selling points is the design changes AMD has instituted in an effort to optimize power consumption while maximizing clock speeds. That mere 5W increase over a HD 7770 GHz Edition for significantly more performance doesn’t come out of thin air.

Much like we detailed in the recent Richland APU Preview, AMD’s new embedded on-die microcontroller is back for an encore presentation. It has the ability to accurately monitor temperatures, voltages and clock speeds along with their relation to ASIC TDP in an effort to determine a combination or factors to ensure optimal performance. These calculations and their respective clock and voltage changes are done at 10ms intervals which is a huge improvement over the previous generation design’s ability to switch voltage rates at 50ms intervals.

In order to make the most out of what this controller brings to the table, AMD has instituted additional P-States within an enhanced version of PowerTune. As before, discrete DPM states dictate voltages and clock speeds based upon proximity to power limit but there are now more of them (eight versus four to be exact) so additional granularity can be inserted into the equation. The result is higher sustained engine clocks in all circumstances rather than select cases.


According to AMD’s the HD 7790 won’t have any reference design and their board partners are being given freedom to experiment. But that hasn’t necessarily led to a vast array of choices since (other than the reference clocked versions that is), we aren’t really seeing all that much variety in clock speeds for factory overclocked editions. For the time being every one of them comes in at 1.075GHz with memory running at 6 Ghz or 6.4GHz. Sure there are plenty of different heatsink designs in the current stable but other than that, differentiation is hard to come by.


Sapphire’s HD 7790 Dual-X OC is of the many examples of board partner cards and this one comes with a custom dual fan heatsink and measures about 8 ¼” long, making it compatible with most cases on the market. It should also achieve some impressive cooling performance since Sapphire has equipped its heatsink with a large-scale aluminum fin array which is fed via a quartet of copper heatpipes. Pricing for this card should be about $159 or $10 more than the reference design which seems more than fair considering its higher clock speeds and custom design.

For the purposes of this review and in keeping with our commitment to never underclock to achieve reference speeds, in order to recreate a stock HD 7790, we flashed a reference BIOS to the Sapphire card. However, the Sapphire results have been left as-is and represent its true performance.
 
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SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
Testing Methodologies Explained

Main Test System

Processor: Intel i7 3930K @ 4.5GHz
Memory: Corsair Vengeance 32GB @ 1866MHz
Motherboard: ASUS P9X79 WS
Cooling: Corsair H80
SSD: 2x Corsair Performance Pro 256GB
Power Supply: Corsair AX1200
Monitor: Samsung 305T / 3x Acer 235Hz
OS: Windows 7 Ultimate N x64 SP1


Acoustical Test System

Processor: Intel 2600K @ stock
Memory: G.Skill Ripjaws 8GB 1600MHz
Motherboard: Gigabyte Z68X-UD3H-B3
Cooling: Thermalright TRUE Passive
SSD: Corsair Performance Pro 256GB
Power Supply: Seasonic X-Series Gold 800W


Drivers:
NVIDIA 314.21 Beta
AMD 13.2 Beta 7
AMD HD 7790 Beta



*Notes:

- All games tested have been patched to their latest version

- The OS has had all the latest hotfixes and updates installed

- All scores you see are the averages after 3 benchmark runs

All IQ settings were adjusted in-game and all GPU control panels were set to use application settings


The Methodology of Frame Time Testing, Distilled


How do you benchmark an onscreen experience? That question has plagued graphics card evaluations for years. While framerates give an accurate measurement of raw performance , there’s a lot more going on behind the scenes which a basic frames per second measurement by FRAPS or a similar application just can’t show. A good example of this is how “stuttering” can occur but may not be picked up by typical min/max/average benchmarking.

Before we go on, a basic explanation of FRAPS’ frames per second benchmarking method is important. FRAPS determines FPS rates by simply logging and averaging out how many frames are rendered within a single second. The average framerate measurement is taken by dividing the total number of rendered frames by the length of the benchmark being run. For example, if a 60 second sequence is used and the GPU renders 4,000 frames over the course of that time, the average result will be 66.67FPS. The minimum and maximum values meanwhile are simply two data points representing single second intervals which took the longest and shortest amount of time to render. Combining these values together gives an accurate, albeit very narrow snapshot of graphics subsystem performance and it isn’t quite representative of what you’ll actually see on the screen.

FRAPS also has the capability to log average framerates for each second of a benchmark sequence, resulting in the “FPS over time” graphs we have begun to use. It does this by simply logging the reported framerate result once per second. However, in real world applications, a single second is actually a long period of time, meaning the human eye can pick up on onscreen deviations much quicker than this method can actually report them. So what can actually happens within each second of time? A whole lot since each second of gameplay time can consist of dozens or even hundreds (if your graphics card is fast enough) of frames. This brings us to frame time testing.

Frame times simply represent the length of time (in milliseconds) it takes the graphics card to render each individual frame. Measuring the interval between frames allows for a detailed millisecond by millisecond evaluation of frame times rather than averaging things out over a full second. The larger the amount of time, the longer each frame takes to render. This detailed reporting just isn’t possible with standard benchmark methods.

While frame times are an interesting metric to cover, it’s important to put them into a more straightforward context as well. In its frametime analysis, FRAPS reports a timestamp (again in milliseconds) for each rendered frame in the sequence in which it was rendered. For example, Frame 20 occurred at 19ms and Frame 21 at 30ms of the benchmark run. Subtracting Frame 20 from Frame 21 allows us to determine how much time it took to render Frame 21. This method would be repeated over and over again to show frame time consistency.

In order to put a meaningful spin on frame times ,we can equate them directly to framerates. A constant 60 frames across a single second would lead to an individual frame time of 1/60th of a second or about 17 milliseconds, 33ms equals 30 FPS, 50ms is about 20FPS and so on. Contrary to framerate evaluation results, in this case higher frame times are actually worse since they would represent a longer interim “waiting” period between each frame.

With the milliseconds to frames per second conversion in mind, the “magical” maximum number we’re looking for is 40ms or 25FPS. If too much time spent above that point, performance suffers and the in game experience will begin to degrade.

Consistency is a major factor here as well. Too much variation in adjacent frames could induce stutter or slowdowns. For example, spiking up and down from 13ms (75 FPS) to 40ms (25 FPS) several times over the course of a second would lead to an experience which is anything but fluid. However, even though deviations between slightly lower frame times (say 10ms and 30ms) wouldn’t be as noticeable, some sensitive individuals may still pick up a slight amount of stuttering. As such, the less variation the better the experience.

Since the entire point of this exercise is to determine how much the frame time varies within each second, we will see literally thousands of data points being represented. So expect some truly epic charts.
 

SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
Assassin’s Creed III / Crysis 3

Assassin’s Creed III (DX11)


<iframe width="560" height="315" src="http://www.youtube.com/embed/RvFXKwDCpBI?rel=0" frameborder="0" allowfullscreen></iframe>​

The third iteration of the Assassin’s Creed franchise is the first to make extensive use of DX11 graphics technology. In this benchmark sequence, we proceed through a run-through of the Boston area which features plenty of NPCs, distant views and high levels of detail.



In a result which is sure to please AMD fans, the HD 7790 is able to eke out a win in a typically NVIDIA-centric title. It also boasts some impressive performance when compared against the HD 7770 GHz Edition.


Crysis 3 (DX11)


<iframe width="560" height="315" src="http://www.youtube.com/embed/zENXVbmroNo?rel=0" frameborder="0" allowfullscreen></iframe>​

Simply put, Crysis 3 is one of the best looking PC games of all time and it demands a heavy system investment before even trying to enable higher detail settings. Our benchmark sequence for this one replicates a typical gameplay condition within the New York dome and consists of a run-through interspersed with a few explosions for good measure Due to the hefty system resource needs of this game, post-process FXAA was used in the place of MSAA.



Although Crysis 3 is one of the most graphics intensive games current available, the HD 7790 handles it without too much of a problem on high detail settings, though it does dip below the 30 fps mark every now and then. More importantly, it thoroughly beats the GTX 650 Ti in the minimum framerate department and leaves the HD 7770 GHz Edition behind in the dust.
 
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SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
Dirt: Showdown / Far Cry 3

Dirt: Showdown (DX11)


<iframe width="560" height="315" src="http://www.youtube.com/embed/IFeuOhk14h0?rel=0" frameborder="0" allowfullscreen></iframe>​

Among racing games, Dirt: Showdown is somewhat unique since it deals with demolition-derby type racing where the player is actually rewarded for wrecking other cars. It is also one of the many titles which falls under the Gaming Evolved umbrella so the development team has worked hard with AMD to implement DX11 features. In this case, we set up a custom 1-lap circuit using the in-game benchmark tool within the Nevada level.



Unfortunately for AMD, NVIDIA cards dominate in this title due to their optimizations for the Directcompute-accelerated global illumination used in Dirt Showdown.


Far Cry 3 (DX11)


<iframe width="560" height="315" src="http://www.youtube.com/embed/mGvwWHzn6qY?rel=0" frameborder="0" allowfullscreen></iframe>​

One of the best looking games in recent memory, Far Cry 3 has the capability to bring even the fastest systems to their knees. Its use of nearly the entire repertoire of DX11’s tricks may come at a high cost but with the proper GPU, the visuals will be absolutely stunning.

To benchmark Far Cry 3, we used a typical run-through which includes several in-game environments such as a jungle, in-vehicle and in-town areas.




In this title, both the HD 7790 and GTX 650 Ti run neck and neck with the overclocked Sapphire card retaining the ability to pull ahead by a hair’s width. Once again though, the HD 7790 provides a perfect gap filling solution between AMD’s HD 7770 and HD 7850.
 
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SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
Hitman Absolution / Max Payne 3

Hitman Absolution (DX11)


<iframe width="560" height="315" src="http://www.youtube.com/embed/8UXx0gbkUl0?rel=0" frameborder="0" allowfullscreen></iframe>​

Hitman is arguably one of the most popular FPS (first person “sneaking”) franchises around and this time around Agent 47 goes rogue so mayhem soon follows. Our benchmark sequence is taken from the beginning of the Terminus level which is one of the most graphically-intensive areas of the entire game. It features an environment virtually bathed in rain and puddles making for numerous reflections and complicated lighting effects.



Hitman Absolution repeats the results we saw in previous tests but this time the HD 7790 is able to pull ahead of NVIDIA’s GTX 650 Ti by a significant amount.


Max Payne 3 (DX11)


<iframe width="560" height="315" src="http://www.youtube.com/embed/ZdiYTGHhG-k?rel=0" frameborder="0" allowfullscreen></iframe>​

When Rockstar released Max Payne 3, it quickly became known as a resource hog and that isn’t surprising considering its top-shelf graphics quality. This benchmark sequence is taken from Chapter 2, Scene 14 and includes a run-through of a rooftop level featuring expansive views. Due to its random nature, combat is kept to a minimum so as to not overly impact the final result.


Even though Max Payne 3 was initially an NVIDIA-centric title, it looks like the GTX 650 Ti is overmatched here and its performance suffers as a result. It could very well be that AMD has found a way to optimize their drivers for this game whereas NVIDIA seems to be falling behind.
 
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SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
Tomb Raider

Tomb Raider (DX11)


<iframe width="560" height="315" src="http://www.youtube.com/embed/okFRgtsbPWE" frameborder="0" allowfullscreen></iframe>​

Tomb Raider is one of the most iconic brands in PC gaming and this iteration brings Lara Croft back in DX11 glory. This happens to not only be one of the most popular games around but it is also one of the best looking by using the entire bag of DX11 tricks to properly deliver an atmospheric gaming experience.

In this run-through we use a section of the Shanty Town level. While it may not represent the caves, tunnels and tombs of many other levels, it is one of the most demanding sequences in Tomb Raider.





This result actually came as a bit of a surprise due to the Gaming Evolved nature of Tomb Raider. However, the last patch from Crystal Dynamics alongside NVIDIA’s latest drivers have helped the GXT 650 Ti significantly. This allows it to outstrip the HD 7790, though the AMD card puts in a valiant effort.

Supposedly a patch will be released in the coming days which increases Tomb raider performance by another 25% so this isn't the last we've seen of this game's potential on both AMD and NVIDIA platforms.
 
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SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
Frame Time Testing (pg.1)

Frame Time Testing


Please note that our complete frame time testing methodology can be found on the Methodologies page. For the purposes of this section, any frame time above 40ms (ie: 25FPS or below) should be considered too slow to maintain a fluid in-game experience.








The first batch of frame time tests show a reflection of what we’ve seen in past reviews but with a bit of a twist. AMD’s HD 7790 still displays a horrible amount of stutter in Far Cry 3, making the game nearly unplayable at some points, but on average it does much better than its higher end siblings. Most games played with a fluidity we haven’t seen from AMD cards in quite some time.

Unfortunately, the exact reasoning behind this somewhat drastic change isn’t quite clear but it may have something to do the actual in-game settings rather than an architectural change.
 
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SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
Frame Time Testing (pg.2)

Frame Time Testing (pg.2)


Please note that our complete frame time testing methodology can be found on the Methodologies page. For the purposes of this section, any frame time above 40ms (ie: 25FPS or below) should be considered too slow to maintain a fluid in-game experience.






Additional testing shows the HD 7790 exhibiting some interesting behavior. In Tomb Raider, it is incredibly docile, even when compared against competing AMD solutions like the HD 7770 and HD 7850. Meanwhile, it still exhibits a noticeable stutter within Hitman Absolution so the previous issues obviously haven’t been ironed out.
 
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SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
Temperatures & Acoustics / Power Consumption

Temperature Analysis


For all temperature testing, the cards were placed on an open test bench with a single 120mm 1200RPM fan placed ~8” away from the heatsink. The ambient temperature was kept at a constant 22°C (+/- 0.5°C). If the ambient temperatures rose above 23°C at any time throughout the test, all benchmarking was stopped..

For Idle tests, we let the system idle at the Windows 7 desktop for 15 minutes and recorded the peak temperature.



Without a true reference card to compare against, it’s almost impossible to properly judge the Sapphire OC’s performance here. However, it is definitely able to post some very low temperature results regardless of the competition’s strengths in this department.


Acoustical Testing


What you see below are the baseline idle dB(A) results attained for a relatively quiet open-case system (specs are in the Methodology section) sans GPU along with the attained results for each individual card in idle and load scenarios. The meter we use has been calibrated and is placed at seated ear-level exactly 12” away from the GPU’s fan. For the load scenarios, a loop of Unigine Valley is used in order to generate a constant load on the GPU(s) over the course of 15 minutes.


Alongside great looking thermal results, Sapphire’s heatsink remained whisper quiet throughout testing. It doesn’t get any better than this for a graphics card that would feel right at home within an HTPC.


System Power Consumption


For this test we hooked up our power supply to a UPM power meter that will log the power consumption of the whole system twice every second. In order to stress the GPU as much as possible we used 15 minutes of Unigine Valley running on a loop while letting the card sit at a stable Windows desktop for 15 minutes to determine the peak idle power consumption.

Please note that after extensive testing, we have found that simply plugging in a power meter to a wall outlet or UPS will NOT give you accurate power consumption numbers due to slight changes in the input voltage. Thus we use a Tripp-Lite 1800W line conditioner between the 120V outlet and the power meter.


The Bonaire core’s claim to fame is its tightly controlled power consumption and our numbers seem to put truth to AMD’s claims. Considering the performance difference, it is incredible to see an HD 7790 consuming as much as an HD 7770 GHz Edition and slightly less than a GTX 650 Ti. It seems like AMD is on the right track here so it should be interesting to see what the upcoming Oland design is able to achieve.
 
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SKYMTL

HardwareCanuck Review Editor
Staff member
Joined
Feb 26, 2007
Messages
12,861
Location
Montreal
Overclocking Results

Overclocking Results


With Sapphire’s HD 7790 already boasting a 7.5% boost in core speeds and faster memory frequencies, we really didn’t’ have all that much available space to play with in AMD’s Overdrive utility since it maxes out at 1200MHz / 6.4 Gbps for the core and memory respectively.

This means Sapphire’s card maxes out the GDDR5 speeds already and we were able to peg core clocks at 1172MHz. So there should be some more left in the tank for secondary overclocking programs to access through additional voltage tuning options.

Naturally, the actual performance from these clock speeds is quite good but it is nonetheless constrained by AMD’s own software limitations.


 
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