AMD's "Dual Graphics" aka Hybrid CrossFire lets you pair an APU with a GPU for improved performance, so we took it for a spin with a Kaveri APU and a budget GPU
We've already written quite a bit about AMD's third-generation APU family, known as Kaveri. It's a CPU with an integrated GPU, just like with Intel's Core i7 parts that contain HD Graphics. The difference is that in the past, AMD paired a relatively weak GPU with the CPU, for predictably lame results. This time around, however, AMD has stepped it up a notch, and put the GPU on equal footing with the CPU, sticking an R7-series GPU inside the package, which is a bit more powerful than anything Intel has to on tap these days (on the GPU side, that is). Also, since AMD makes both CPUs and GPUs, it can one-up Intel by letting both pieces of silicon work together in a partnership dubbed Dual Graphics, which used to be known as Hybrid CrossFire. It's a dual-GPU setup combining integrated and discrete graphics, and it could be a good way to give your integrated graphics a healthy boost, or it could be a total waste of money. This month, we decided to build a budget-oriented gaming machine to find out for ourselves what Dual Graphics is all about, and to see whether it's actually useful, or just marketing BS.
Preparing to Dual
All you need to build a machine that uses AMD Dual Graphics is the right APU and GPU, and naturally, AMD has a list of compatible and recommend pairings on its website. The selection is actually quite limited, and when we asked AMD what criteria it uses to deem a particular APU and GPU "compatible," the response was, "We test the different configurations and the best user experiences based on smoothness and performance are listed as the recommended pairing." The company noted, "similarity in outright performance but also configuration" as the main criteria, and listed the A10-7850 and R7 250 as a perfect example, since both have 8 GCN units, the same memory bus width, and similar clock speeds. Due to this recommendation, we decided to use it for this particular build. With the A10-7850 selected, we decided to plop it into a Gigabyte G1.Sniper A88X motherboard, since it's a top-shelf gaming board, supports Dual Graphics, and has dual PCIe x16 slots in case we want to add a baller GPU or two some day in the future. This is a budget machine with modest power requirements, and our discrete GPU doesn't require a six-pin power connector, so we opted for a 430W Smart PSU from Thermaltake, which is the wattage we consider the minimum for a gaming box. Storage duties are handled by an Intel 335 Series SSD, which is SandForce-based. It's not the fastest SSD on the bench, but it's reliable and affordable. Since it's a budget box, we stuffed it all into Antec's newest entry-level military-themed chassis, the GX700. It's similar to the Corsair C70, but half the price.
INGREDIENTS
| | PART | Price |
| Case | Antec GX700 | $60 |
| PSU | Thermaltake Smart 430w | $45 |
| Mobo | Gigabyte G1.Sniper A88X | $120 |
| CPU | AMD A10-7850K | $175 |
| Cooler | Stock | $0 |
| GPU | MSI Radeon R7 250 | $90 |
| RAM | 2x 4GB Corsair Vengeance | $95 |
| SSD | Intel 335 Series240GB | $160 |
| OS | Windows 8.1 64-bit OEM | $100 |
| Total | | $845 |
Click the next page to see our CPU, motherboard, and video card specs
1. Case Working
Building in the GX700 was refreshingly painless, thanks to a roomy interior, large grommets for cable routing, and plenty of room to work. Since we weren't planning on overclocking our A10-7850 APU, we went with the simplest cooling option available to us—a stock AMD cooler. These coolers don't look so hot, but they do a great job of keeping the CPU cool, and they operate quietly. Its small size also makes connecting things around the CPU socket a walk in the park. We did splurge a bit on the RAM, though, going with 8GB of Corsair Vengeance with extra-tall heatsinks. These guys are a tiny bit more expensive than the LP sticks with the low-profile heatsinks on them, but either one would work.
2. Hiding Wires
One of the building "tricks" we like to use, if you can call if that, is to stick all the power cables that come from the front of the case to the back of the chassis, and then let them poke out right where they are connected. This keeps the interior uncluttered, and theoretically improves airflow around the power supply, since the cables aren't arranged in a rat's nest at the bottom of the chassis. We like the space between the SATA ports on this motherboard, too, and the fact that they are on the bottom of the motherboard instead of along the edge like they usually are. Anyone who has installed a slightly long GPU knows what a PITA it can be to access those ports with a GPU covering that area of the motherboard. We also like the fact that there are eight SATA 6Gb/s ports on this motherboard instead of six you get with a Z87 motherboard.
3. Give me the code
Probably the most glaring nod to this case's military theme is the yellow-and-black striped cover that sits on top of the case. Lifting this cover exposes a red switch, which is actually a fan controller that can handle up to four fans. Three fans are already in the case, with two 140mm units up top where a radiator could reside one day, and one 120mm rear fan exhausting heat. You can also install up to two 120mm front intake fans, and one 120mm fan on the side door to help cool the GPU. Next to the fan controller are four USB ports—two USB 2.0 and two USB 3.0—and headphone and mic jacks.
4. The bad news
Maybe we're spoiled, but we're used to just pressing down on a front filter like this one and having it pop away from the case for easy removal. On this chassis, though, the metal grill that covers the front air filter is attached via four thumbscrews. You can loosen the screws with your thumbs just like their name implies, but we found we had to use a screwdriver to get them all the way out. Once removed, the air filter is held into place by clips, reminding us of this case's rock-bottom price tag of just $60. There are no free lunches, so saving money on a PC build means you lose a few amenities, such as tool-less filter covers. To install a 120mm fan, you'll need to remove the entire front cover, which can be lifted away with a bit of effort.
5. More bad news
Here's another odd design choice from Antec: these weird metal clips that hold the covers on the 5.25-inch bays. When you pull the clips out of the way, the cover loosens and falls right out of the slot. Both the clips and the way the covers tumble out when free felt extremely cheap. Plus, the top drive bay is blocked internally by all the cabling that dangles down from the top-mounted USB and fan controller cables, so you can't put an optical drive in that particular slot, but you could put in a card reader or something similar. The mechanism that holds the drives in place is toolless, however, so you just need to slide it to lock the drive into place. It's not the most sturdy design, but it worked well enough for our needs. Just below the 5.25-inch drive bays there is a vertical cage made of metal that holds five drives in either 3.5- or 2.5-inch form factor. You need to install drives from the right side of the case, however, as the mechanism that releases the individual drive bays resides behind the cage.
6. Cool Under Pressure
We'll be honest: When we first configured this build, we slotted a 650W PSU into the bottom of the chassis because, well, this is Maximum PC and that's how we roll. Upon reflection, however, we realized that was a bit of overkill, especially since we had one SSD, no optical drive, and didn't need any power for our discrete GPU. Since we always tell people not to buy more PSU than they need, we decided to take our own advice and just go with a 430W unit from Thermaltake. We've used its PSUs in our GPU testing machine for the past two years with no issues, so it's a brand we generally trust. The area below the PSU is well-ventilated, and includes a filter that is easily removable, too. It sticks out a tiny bit behind the chassis, so you just have to pull it out as if you were sliding a card out of a deck, give it a good wash, and slide it back into place. You can also see that we could have fit a slightly larger PSU into this area.
A Golden Triangle
The purpose of this build was to find out how the addition of a second GPU to a Kaveri APU machine worked, and to see whether or not it was worth the money. Once our rig was built, we added the $90 R7 250 GPU, and then tested both the GPU by itself, and then paired with the APU. Once the system was humming along, enabling Dual Graphics was as simple as ticking a box in the Catalyst Control Center, much like you would do if you were enabling regular CrossFire with two discrete GPUs.
To put it through its paces, we ran our tests suite at 1080p with all settings maxed out, but no AA because that's just a bridge too far for these cards. With Dual Graphics enabled, we were surprised to see performance go up as much as it did, which was around 40 to 50 percent in most titles that were able to use both GPUs. That is damned impressive, and more than we expected. The problem, of course, is that the overall numbers were still really low despite two GPUs working together. When we tested the R7 250 in the May 2013 issue, we noted that it couldn't quite do 1080p with all settings maxed, but we hoped the addition of the second GPU would allow us to overcome that challenge. Unfortunately, it's not enough, so any of these low-end cards are not ready for 1080p gaming—they're better suited to 720p or 1050p.
The bigger question here is if you were running a Kaveri box and decided you wanted to add more GPU muscle, what are you going to do? We can say definitively that if you want to really increase performance, you should just buy a discrete GPU like the R7 265 and forget about integrated graphics, or sub-$100 GPUs because they generally suck, at least if you are like us and used to gaming with all details enabled. It's possible that over time, AMD will work to improve the scaling between the two GPUs in Dual Graphics, so instead of seeing gains around 40 percent, we'll see it more around 75 percent, like it is with two discrete cards.
With all that said, we were impressed by both how easy it was to set up Dual Graphics, and that we saw a very noticeable gain in almost all of our test games. We don't think the combination of two weak GPUs is enough to provide a decent gaming experience, though, so in the final analysis, we'd rather just use a more powerful discrete GPU.
Benchmarks | | ZERO POINT | |
| 3DMark | 711 | 1,043 |
| Batman: AO (fps) | 20 | 28 |
| Heaven 4.0 (fps) | 10.6 | 10.8 |
| Unigine Valley (fps) | 13 | 14 |
| Tomb Raider (fps) | 11.5 | 16.2 |
| Hitman: Absolution (fps) | 16 | 24 |
The zero-point machine compared here consists of a 3.2GHz Core i7-3930K and 16GB of Corsair DDR3/1600 on an Asus P9X79 Deluxe motherboard. It has a GeForce GTX 690, a Corsair Neutron GTX SSD, and 64-bit Windows 7 Professional.
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