Date: Friday , March 22, 2013
Today marks the first desktop GPU launch from AMD for 2013. AMD is refreshing us today with a video card marked for the lower-end of the spectrum, in the sub-$200 video card category. AMD is launching, with availability in April, the AMD Radeon HD 7790. As you can tell from the product description, this video card is poised to be the middle man between the Radeon HD 7770 and the Radeon HD 7850, which had existed a fairly large gap between the two, until now. The AMD Radeon HD 7790 has a set MSRP for 1GB models at $149.
Let's backtrack a little bit first, and talk about the Radeon HD 7770 and the Radeon HD 7850. We have reviewed a few Radeon HD 7770's here in the past, but mostly we didn't evaluate a lot of these video cards given the price range. The Radeon HD 7770, or "Cape Verde" as it's known, was released on February 14th of 2012, more than a year ago. The Radeon HD 7770 was launched with an MSRP of $159. As you can see, with over a year of service, it is about time this video card was moved out and refreshed. Current prices today have the Radeon HD 7770 sitting as low as $115 online, with rebates taking it under $100. Certainly, it has benefited from these price drops. The Radeon HD 7770 was often considered under powered, even at the time it was launched. It did have one unique thing for the time, it ran at 1GHz clock speed, which gave it the GHz Edition name. The Radeon HD 7790, launching today, is going to cut in $10 under where the HD 7770 fell, at $149 on launch.
Now let's talk about the Radeon HD 7850 a bit, since the Radeon HD 7790 is going to cut in-between these two video cards. The Radeon HD 7850, also known as "Pitcairn", was released on March 5th, 2012. This means the Radeon HD 7850 has also been out over a year. The Radeon HD 7850 was launched with an MSRP of $249. Already you can see a huge gap existed price wise, between the Radeon HD 7770 and Radeon HD 7850, a $100 price gap. Not only that, but performance differences were huge between the Radeon HD 7850 and the Radeon HD 7770. For one, there was a 60% difference between stream processor count, a 60% difference between texture units and a 100% difference between ROPs. The memory bandwidth was also very different, with the HD 7770 having a 128-bit bus and the HD 7850 having a 256-bit bus.
The Radeon HD 7790 is a call to fill the gap between these two video cards, and give gamers a better $149 experience in 2013.
The Radeon HD 7790, also known as "Bonaire", is a half-generation, of sorts. This GPU utilizes an updated Graphics Core Next (GCN) architecture. However, it is not a major departure from GCN 1.0. In fact, it just has a few evolutionary upgrades, and is not, we repeat not, a major generational change. The GPU is manufactured at 28nm and contains 2.08 billion transistors.
AMD states that this is a new piece of silicon that has been in the works for quite a while, to address the position between the HD 7770 and HD 7850. The new Radeon HD 7790 is 160 square mm, compared to the Radeon HD 7770 which was 123 square mm. The Radeon HD 7790 runs at 1GHz, but is not going to be called a "GHz Edition" anymore. AMD feels that they have made the point about having 1GHz edition GPUs in the market in 2012, and did not feel a need to label this new one a GHz Edition. Therefore, it will just be known as Radeon HD 7790.
The Radeon HD 7790 consists of 896 stream processors, this is up from 640 on the Radeon HD 7770. The texture units have also been increased to 56 from 40, but the ROPs stay the same. What makes this architecture unique, is that on the HD 7790 it can do 2 primitives per clock, versus 1 primitive per clock on the HD 7770. This all brings the fill rate up to 1.79 TFLOPS, versus 1.28 TFLOPS on the HD 7770 and also increases the fillrate up to 56 GT/s versus 40.
However, the memory bus stays the same at 128-bit wide with 1GB of GDDR5. The engine clock also stays at 1GHz. The memory itself has been clocked higher, running at 6GHz now versus 4.5GHz. This gives us 96GB/sec of bandwidth versus 72GB/sec. With all of these improvements the total board power is only 5W higher at 85W versus 80 on the HD 7770. The HD 7790 does natively support six displays from the ASIC.
There are a few notable architectural changes compared to the Radeon HD 7770 worth talking about. As noted, the new HD 7790 has dual geometry and tessellation engines, which is a 2x improvement over the HD 7770. The HD 7790 can do 2 primitives per clock versus 1 on the HD 7770. There are also changes to PowerTune, which we will talk about below. Beyond that, there are some more smaller instruction changes to the architecture, but they are so minor that it doesn't really affect anything gamers will benefit from.
PowerTune has been updated to provide higher sustained clocks, better voltage regulation, saving you power and at the same time providing more performance. There are eight clock/voltage states in the HD 7790. The GPU is capable of changing through these states at a rate of 10ms. With the states changing between high frequencies, and lower frequencies, an effective clock becomes apparent. In practice, we haven't seen this really affect the clock speeds yet. Our card is clocked at 1075MHz, and we saw this at all times in the games we played. Overclocking is most likely where you will run into possible TDC and TDP limits.
Here is a list of manufactures and some SKUs that are coming out. Note that all of them are 1GB models. It is possible some manufacturers will produce 2GB models, but that is completely up to the manufacturer. Standard units will all have 1GB.
Today, we are evaluating the ASUS Radeon HD DirectCU II OC. This is a DirectCU II card from ASUS, using its standard DirectCU II cooler, which we have come to enjoy as being an effective cooling solution. This model is overclocked, it runs at 1075MHz versus the standard 1000MHz. The memory is also overclocked to 6.4GHz versus 6GHz. This should give us a slight boost in performance, but don't expect it to change playable settings.
As you can see, the actual Printed Circuit Board (PCB) is shorter than the heatsink and fan assembly. The PCB measures almost 7 inches long, but the heatsink extends out a total of 8.5 inches long. There is one PCIe connector at the back, which is easy to get to and unplug. There is one DVI-I and one DVI-D port, and one HDMI and one DisplayPort. CrossFire is supported on this video card.