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The 990FX Chipset Arrives: AMD And SLI Rise Again
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1. 990FX: Socket AM3+ Meets SLI

Generally, platform reviews accompany new processors. But in the case of AMD’s 990FX chipset, there’s both good and bad news.

The good news is that AMD still has a fantastic compatibility story. So, 990FX supports today’s Socket AM3 processors and the upcoming AM3+ CPUs based on the Bulldozer microarchitecture.

The bad news is that those Bulldozer-based chips are still not ready. Processors based on the B0 stepping are in the hands of motherboard manufacturers. But they’re all telling me that performance is nowhere near what they were expecting, and it’ll take another stepping to fix them.

Those 2011 sockets correspond to Zambezi, Llano, and the Brazos processors. Those 2011 sockets correspond to Zambezi, Llano, and the Brazos processors.

Technically, you could buy a 990FX-based motherboard today and drop in an existing Phenom II. But if you’re really lusting after a six-core Zambezi-based chip, it’d be better to simply wait a couple of months. Unless there was another reason to upgrade…

990FX: Same As 890FX, But Guaranteed Compatibility

The 990FX chipset employs the same silicon as 890FX. Didn't know today's launch was happening? Didn't know 990FX would be so similar to 890FX? If you were following me on Twitter, you would have! ;)

According to AMD, it’s incrementing the platform name to clarify compatibility with Bulldozer-based processors. When you see a board that centers on 990FX, the company wants you to know that its upcoming AM3+ CPUs are drop-in-compatible (again, 990FX-based boards will also take existing AM3 chips).

Why yes, I did Photoshop an 890FX block diagramWhy yes, I did Photoshop an 890FX block diagram

You need the 942-pin Socket AM3+ (AM3b) interface, though, in order to support Zambezi’s power and frequency management features.

Conversely, AM3+ processors also drop into Socket AM3 motherboards, given a BIOS update. Depending on the company that manufactured your AM3-enabled board, there may or may not be a firmware upgrade available immediately. So, understandably, AMD doesn’t want to leave the question of compatibility up in the air.

Update (4/29/2012): Much time has passed since AMD made the claim that AM3+-based processors would drop into Socket AM3-equipped motherboards. A few models with AM3 interfaces do support CPUs centering on AMD's Zambezi design, but most do not. If you own a platform with an AM3 interface, check before buying an FX processor. More than likely, you'll need a new motherboard with Socket AM3+.

Even with a new firmware, though, you won’t get those aforementioned features on an AM3 platform. Also, 890FX and 990FX both support HyperTransport 3.0 with transfer rates of up to 5.2 GT/s. According to MSI, 990FX adds HyperTransport 3.1 support with signaling up to 6.4 GT/s (apparently something we’ll see from the eight-core Zambezis).

I’m not a fan of rebadging, but in this case, it’s a necessary evil. Sure beats murdering a processor interface every time you introduce a new architecture (*cough* Intel). Most enthusiasts will probably want to upgrade anyway to match Zambezi and AM3+. But it’s nice to know that AMD has its eye on the backward and forward compatibility of its processors and platforms.

SLI: A Pleasant Surprise

More pertinent than any AM3+ discussion, at least today, is the addition of SLI support on 990FX boards. Frankly, there’s nothing stopping the motherboard guys from licensing SLI on 890FX as well, but nobody I’ve talked to has plans to do that. Instead, it looks like SLI will be used as a differentiator to get gamers stoked about upgrading their processor and motherboard when the FX-series (Zambezi) chips launch.

GeForce GTX 570 SLI on 990FXGeForce GTX 570 SLI on 990FXPhenom II X4 980 on 990FXPhenom II X4 980 on 990FX

As with Z68 Express, two-way SLI and CrossFire configurations are easily supported. AMD’s 990FX hits with 42 PCI Express lanes, giving each slot on a dual-card config its own 16-lane link (compared to Intel’s two x8 links). Don't get too worked up about this "advantage." Eight lanes is still enough for Intel's parts to compete aggressively. Don't believe me? Check out Thomas Soderstrom's three-part series on multi-card scaling.

Because 990FX boasts so much second-gen PCI Express connectivity, it doesn’t require NF200 to support three-way setups, though. Both of the 990FX boards that landed in our lab accommodate two- and three-way configurations (x16/x8/x8), along with quad-GPU arrangements using cards like GeForce GTX 590 and Radeon HD 6990.

GeForce GTX 570 SLI on Z68GeForce GTX 570 SLI on Z68Core i5-2400 on Z68Core i5-2400 on Z68

Without AM3+ processors to test, today’s 990FX launch only has one really interesting angle: SLI-based performance using a Phenom II X4 980 versus Intel’s Core i5-2400, both configurations armed with a pair of GeForce GTX 570 graphics cards. The comparison couldn’t get any more even. Our P8Z68-V Pro sells for the same $210 Asus plans to ask for the Sabertooth 990FX, and the Core i5-2400 sells for $5 more than AMD’s Phenom II X4 980. With all other components equal, this is a true head-to-head.

So, is the return of SLI support to AMD’s chipset family worth an upgrade? Let’s find out!

2. 990FX Boards From Asus And MSI

We received two platforms ahead of today’s roundup. One arrived early from Asus, and the other showed up a little later from MSI. Because we had the Asus board set up and running tests already, that’s the one we used for benchmarking.

Asus Sabertooth 990FX

Asus is estimating that its Sabertooth 990FX will cost $209—the same price, incidentally, as the P8Z68-V Pro motherboard we’re using for comparison.

The board supports up to four GPUs using two cards, or up to three-way CrossFire or three-way SLI. As with the 890FX before it, 990FX feature 42 lanes of second-gen PCI Express, 32 of which can be used on a pair of graphics cards. Technically, the chipset also supports four cards with eight lanes apiece, but Asus doesn’t support that configuration, instead running up to three discrete cards at x16/x8/x8.

Complementing 990FX is AMD’s SB950 southbridge. Contrary to early rumors, this part doesn’t support USB 3.0 (that’ll have to wait until AMD’s first Fusion Controller Hubs debut next month). No, SB950 is, again, identical to its predecessor, which means Asus has to add USB 3.0 through a pair of ASMedia controllers. Fortunately, the AMD southbridge carries over SB850’s six SATA 6Gb/s ports, and all of those are exposed along the board’s bottom-right edge, along with two 3 Gb/s connectors enabled by a JMicron JMB362. A second JMicron controller facilitates two eSATA ports.

Of course, Asus adds its own unique mix of features to the board as well. This platform is shuffled into the TUF series, which emphasizes stability and durability. We’re happy to report that the Sabertooth 990FX did, in fact, operate flawlessly through testing. Should it become part of your next build (rather than a subject on our open-air bench), you’ll be happy to know it features a total of six fan headers, 10 thermal sensors, and a feature Asus calls TUF Thermal Radar, used to identify hot spots and adjust fan performance in response.

MSI 990FXA-GD80

We didn’t have time to run MSI’s 990FXA-GD80 through the same gauntlet as the Asus board, but we still wanted to show off the difference between both platforms. Whereas the Sabertooth’s focus is clearly on reliability and subdued, earthy colors, MSI spices things up with its dark blue/grey/black motif.

From a functionality standpoint, MSI includes most of the same capabilities as Asus—notably three-way SLI and CrossFire support, that black AM3b socket interface, plenty of USB 3.0 connectivity, and six 6 Gb/s SATA ports emanating from the SB950 southbridge.

MSI is short one internal SATA 3Gb/s controller versus Asus’ implementation. However, the 990FXA-GD80 does include onboard power/reset buttons—a feature awkwardly missing from the Sabertooth.

3. Hardware And Benchmark Setup
Test Hardware
Processors
AMD Phenom II X4 980 Black Edition (Deneb) 3.7 GHz (18.5 * 200 MHz), Socket AM3, 4 GT/s HyperTransport, 6 MB Shared L3, Power-savings enabled, 125 W

Intel Core i5-2400 (Sandy Bridge) 3.1 GHz (31 * 100 MHz), LGA 1155, 6 MB Shared L3, Power-savings enabled, 95 W
Motherboards
Asus Sabertooth 990FX (Socket AM3+) 990FX/SB950, BIOS 0138

Asus P8Z68-V Pro (LGA 1155) Z68 Express PCH, BIOS 0401
Memory
Crucial 8 GB (2 x 4 GB) DDR3-1333, MT16JTF51264AZ-1G4D1 @ 9-9-9-24 and 1.65 V
Hard Drive
Intel SSDSC2MH250A2 250 GB SATA 6Gb/s
Graphics
Nvidia GeForce GTX 570 in SLI
Custom GeForce 270.77 Driver
Power Supply
Cooler Master UCP-1000 W
Games
Lost Planet 2
Highest Quality Settings, No AA / No AF, 4x MSAA or 32x CSAA / 16x AF, vsync off, 1680x1050 / 1920x1080 / 2560x1600, DirectX 11, Steam version, Test A
Just Cause 2
Highest Quality Settings, No AA / 2x AF, 8x AA / 16x AF, vsync off, 1680x1050 / 1920x1080 / 2560x1600, Bokeh filter and GPU water disabled (for Nvidia cards), Concrete Jungle Benchmark
Metro 2033
High Quality Settings, AAA / 4x AF, 4x MSAA / 16x AF, 1680x1050 / 1920x1080 / 2560x1600, Built-in Benchmark, Depth of Field filter enabled, Steam version
F1 2010
Ultra High Settings, No AA / No AF, 8x AA / No AF, 1680x1050 / 1920x1080 / 2560x1600, Steam version, Custom benchmark script, DX11 Rendering
Aliens Vs. Predator Benchmark
High Quality Settings, SSAO, No AA / 16xAF, Ultra Quality Settings, 4x MSAA / No AF, vsync off, 1680x1050 / 1920x1080 / 2560x1600
Battlefield: Bad Company 2
Custom (Highest) Quality Settings, No AA / No AF, 8x MSAA / 16xAF, 1680x1050 / 1920x1080 / 2560x1600, opening cinematic, 145 second sequence, FRAPS
3DMark 11
Performance Default
World of Warcraft: Cataclysm
Ultra Quality Settings, No AA / 16x AF, 8x AA / 16x AF, From Crushblow to The Krazzworks, 1680x1050 / 1920x1080 / 2560x1600, FRAPS, DirectX 9 Rendering
4. Benchmark Results: 3DMark 11

The overall chart for 3DMark 11 indicates that, at the Performance setting, Intel’s Z68-based platform has an advantage. This advantage quickly evaporates when graphics details are pushed to Extreme.

Even when you’re talking about two drastically-different processor architectures and the massive performance of a pair of GeForce GTX 570s in SLI, graphics horsepower is still the bottleneck at the end of the day.

This is proven in both Graphics scores, where the GPU subsystems keep even pace with each other.

Conversely, the Physics benchmark favors Intel’s setup. And when you take demanding 3D workloads out of the picture, the numbers don’t change much in shifting from Performance to Extreme.

Finally, in the Combined suite, we see a potent processor help Intel in the less-demanding test, while an elevated graphics workload evens things out in the Extreme metric.

5. Benchmark Results: Metro 2033 (DX11)

Metro is an absolute beast when it comes to taxing graphics performance. Applying the depth of field effect, especially, has a profound impact on frame rates, as each card is hit with a DirectCompute task that literally cuts results in half.

It’s really not a surprise, then, that it doesn’t matter if you’re running a Core i5 at 3.1 GHz or a Phenom II at 3.7 GHz—both solutions yield comparable performance when they’re backed by a pair of GeForce GTX 570s in SLI.

6. Benchmark Results: Lost Planet 2 (DX11)

In contrast to Metro, Lost Planet 2 (also a DirectX 11-enabled title) is much more sensitive to platform performance.

We’d expect any performance difference to be most pronounced at 1680x1050, and it is. With AA on or off, there’s a pretty noticeable delta that favors Intel’s Z68-based configuration.  

At 1920x1080, there’s still a pretty wide margin between Intel’s Core i5 and AMD’s fastest Phenom II. That gap narrows a bit once anti-aliasing is applied, though, and more of the emphasis is placed on graphics performance.

By the time we hit 2560x1600, both builds perform comparably. From there, it’d take a more powerful graphics setup to help alleviate the clear bottleneck: our GTX 570s in SLI.

7. Benchmark Results: Aliens Vs. Predator (DX11)

Like Metro 2033, Aliens vs. Predator is constrained by graphics performance at all three resolutions, with and without anti-aliasing applied.

Thus far, we have “it doesn’t matter” as an answer to the question, “which platform should I buy for my next SLI-based build?” in two real-world games. One game and one synthetic metric claim otherwise.

8. Benchmark Results: Battlefield: Bad Company 2 (DX11)

Chalk up another title able to show Intel’s platform outperforming AMD’s. Ultimately, though, anti-aliasing is the equalizer at each tested resolution.

Clear and measurable performance gaps separate our Core i5-2400/Z68 and Phenom II X4 980/990FX machines at 1680x1050, 1920x1080, and 2560x1600 without AA turned on. Factor in anti-aliasing and anisotropic filtering, though, and there’s really little difference at any of those three resolutions.

9. Benchmark Results: F1 2010 (DX11)

We knew this was coming, because we’ve seen it several times before. For some reason, AMD-based platforms have a problem with F1 2010 in that they cannot break past 63ish frames per second. No, it’s not a v-sync issue. Swap the exact same setup over to an Intel platform, and suddenly we get much better numbers.

This won’t be the first time we see 990FX hamstrung in this story; it’s one of the more worrying indicators that SLI on an AMD platform might not be as rosy of a proposition as we might have hoped.

As a result of that 60-ish FPS cap, Intel’s lead at 1680x1050 is tremendous. It’s just as significant at 1920x1080. Stepping up to 2560x1600 normalizes performance a bit, but Core i5 still leads with and without anti-aliasing enabled.

10. Benchmark Results: Just Cause 2 (DX11)

The same thing (almost) happens in Just Cause 2. AMD’s Phenom II gets stuck right around 45 frames per second, regardless of resolution. And although we apply anti-aliasing and anisotropic filtering, neither feature has much of an effect on performance, indicating that our two GeForce GTX 570s still have more to give here. Something else is artificially limiting these results.

Intel’s platform hits a ceiling at a higher frame rate—typically around 60 frames per second. It’s only really at 2560x1600 with AA and AF cranked that performance takes a more significant ding.

11. Benchmark Results: World Of Warcraft: Cataclysm (DX11)

Our relationship with Blizzard’s World of Warcraft goes back a ways. Back in December of last year, I took a first look at the Cataclysm expansion pack with experimental support for DirectX 11 in World Of Warcraft: Cataclysm—Tom’s Performance Guide. Recently, that support was integrated into patch 4.1, under the game options menu. It's now official, and if you have a DX11-enabled card, I recommend you use it. If you need to ask why, check out the performance guide. Frame rate boosts can be quite surprising.

In our initial testing, we discovered that AMD’s processors were definitely limiting performance in this game. The average frame rate of the Phenom II X6 at 3.7 GHz was 60 frames per second.

Today we see that, with proper support for SLI in place, AMD’s platforms hit 75 frames per second or so. But it doesn’t matter if you run at 1680x1050 or 2560x1600, or if you use 1x multisampling or 8x. Simply, the frame rate doesn’t change. AMD’s processors are still the “problem,” for as much as 75 FPS can be considered problematic.

We’re really only concerned because Intel’s CPUs do so much better, exceeding 100 FPS at 1680x1050 and 1920x1080, only dipping under at 2560x1600 with 8x MSAA turned on.

12. Conclusion

I think that anyone who was hoping to see Bulldozer-based Zambezi processors hit store shelves in conjunction with this year's Computex show in Taipei is going to be disappointed by AMD’s 990FX platform. It’s 890FX, with a new name to show forthcoming AM3+-based processors will work right out of the box.

There’s nothing wrong with that, though. In fact, I’m glad AMD came up with a way to show its customers how to get the most out of an upcoming processor without complicating the upgrade process. Enthusiasts who actually can be troubled to do their homework know that 890FX/990FX and AM3/AM3+ share mechanical compatibility, though it’ll take 990FX and AM3+ to exploit Zambezi’s power/frequency management features. No doubt 800-series boards will start becoming scarcer as the industry gears up to support AM3+.

As we all wait to see what the company’s torch-bearing architecture can do, motherboard manufacturers are throwing us a little bone by licensing Nvidia’s SLI technology for use on 990FX-based platforms. Is the capability worth ditching your old 890FX board and buying an upgrade?

That depends on how loyal you are to Nvidia. Now that AMD’s CrossFire performance is much-improved, there’s no real reason to shy away from multi-card configs from either vendor unless your trepidation comes from multi-card configs themselves.

What concerns us, though, is that in a direct comparison to a similarly-priced platform based on Core i5-2400 and Z68 Express, the Phenom II X4 980 Black Edition hit performance ceilings in a number of benchmarks where the GeForce GTX 570s in SLI still had performance left to offer. Intel’s higher frame rates proved that the graphics cards weren’t to blame.

To that end, I really don’t see a reason to buy 990FX right now. If your priority is top performance in multi-card configurations, you’re buying an Intel-based platform. And if you’re in the market for a fast AMD machine, you’d be doing yourself an injustice by not waiting however long it takes for the Bulldozer-based Zambezi to materialize.

We’re definitely hopeful that the licensing of SLI means AMD’s Scorpius platform will perform well. Now’s not really a good time to build a new gaming machine on Phenom II, though. So, today’s 990FX launch ends up being a bit of a tease. We know what’s coming; we just want it to get here already.