Phenom Goes Triple-Core: AMD's Phenom X3 Processors April 22, 2008 Chris Crazipper Angelini

Introduction

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Well, at least they used to be. Now performance enthusiasts have to weigh clock speed and cores against budgets. Fortunately, single core chips join Paris Hilton and Lindsay Lohan as B-list accessories, leaving you with a choice between dual- and quad-core CPUs. But which to choose? We’ve been promised over and over that there’s software just over the horizon able to show off what four cores can do. At least as far as games are concerned, however, faster frequencies show better than multiplied resources. Then there’s the multi-tasked usage model. Advocates of parallelism argue that quad-core CPUs give you that much more horsepower to run several screens full of apps. Sounds good in theory, but the claim is much more difficult to quantify.

Whatever is the torn gamer with expenses to do? AMD thinks its triple-core Phenom X3 is the answer. Or, at least an answer. The X3s are cut from the same silicon wafer as the Phenom X4. Rather than shipping with all four cores active, however, AMD shuts one of them off at the factory. The result is a slightly awkward three-core configuration priced right between AMD’s dual- and quad-core offerings—perfect, the company says, for folks looking to take a mainstream platform and perhaps mix in an inexpensive gaming card. It also makes a nice alternative to Intel’s comparably-priced dual-core chips, which might not be as nimble when you start piling on the processes.

Of course, the X3s also take the processor market one step closer to looking like the incredibly diverse graphics landscape. We’re naturally glad to have plenty of choices, but at what point does copious selection turn into an overwhelming, overlapping shotgun-blast of speeds, cores, caches, and price tags?

The short of it is that we’re close. In fact, it’s a darn good thing you can’t do half-cores, though we certainly hope the marketing minds at AMD don’t start thinking about cutting their caches in half to create another 10 models.

But it appears that the struggling CPU vendor has indeed found a stretch of the pricing spectrum currently underserved by its multi-core offerings. You see, the quad-core Phenom X4 chips range from $209 to $235 (we’re ignoring the $251 X4 9600 because, quite frankly, you shouldn’t buy it in the face of faster 50-series chips available for less money). The dual-core X2s range from $68 to $178—seemingly right up to where the Phenoms pick up. Remember, though, that the X2s aren’t based on the K10 platform so they don’t benefit from faster HyperTransport settings, a shared L3 cache, or the dual power planes.

Thus, the Phenom X3 family gives you a handful of options centering on the most current architecture. It effectively trades clock speed for parallelism when compared to the X2s, and parallelism for price versus the X4s. Should you be factoring all of those trade-offs into your next processor purchase, though? We’re wondering the same thing.

A Fleet of X3s

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The Lineup, Explained

AMD is rolling out three triple-core Phenom X3 processors, nestled in tightly against the price tags of its fastest dual-core models. The Phenom X3 8750 runs at 2.4 GHz, the X3 8650 runs at 2.3 GHz, and the X3 8450 runs at 2.1 GHz.

Notice that the trio belongs to AMD’s 50-series. That is, the last two numbers of each chip’s model designation ends in 50, invoking the B3 silicon revision, which fixes a cache problem plaguing older Phenom processors. We’ve heard AMD representatives make mention of some other tweaks to B3 unsubstantiated by details. Even still, if you buy a Phenom, make sure it’s one of the new 50s.

Power to the Phenoms

Manufactured on AMD’s 65nm SOI node, the Phenom X3 die consists of roughly 450 million transistors occupying 285 square millimeters of silicon real estate. AMD says that one processing core is turned off completely, though. So you’re not actually powering all 450 million transistors—and it wouldn’t be fair to simply subtract one-quarter of them, since the full 2MB L3 repository is still intact.

Nevertheless, the result is a processor that, according to AMD, runs cooler—at comparable clocks—than the Phenom X4. The company’s own specifications show the difference. A Phenom X4 9750 running at 2.4 GHz features a 125W TDP. The Phenom X3 8750 running at the same frequency is rated at 95W. That’s a 30W savings at the cost of one core. It’s worth noting that those savings come from AMD’s ability to run the 2.4 GHz Phenom X3 at a lower nominal voltage than the Phenom X4.

Just to triple-check, we fired up our test bed with both processors and compared numbers. What we found was a closer to 50W difference. Under load, the Phenom X3 machine was eating 300W of power. Meanwhile, the X4-equipped platform was pushing 355W.

While the 95W Phenom X3 family might not be a play on power savings, AMD is indeed shutting off power to that fourth core. Hmm. Perhaps that’ll help our overclocking efforts.

Overclocking, Pricing, and System Setup

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Overclocking the 9850 Black Edtion

Months into its young life-cycle, the Phenom processor family is already known for a few things. Overclocking headroom is not one of them. The revision B2 chips were generally good for a couple hundred megahertz. Revision B3 processors might be slightly better on average, though our Phenom X4 9850 sample did a meager 300 MHz (that’s meager in comparison to Intel’s 45nm Core 2 Duo E8500, which cranked out an extra 1 GHz).

We consequently weren’t expecting much from the Phenom X3 8750 AMD sent over. Could it possibly be, though, that the elimination of a single core could help improve our overclocking results? That’s a significant chunk of circuitry turned off, after all—several million transistors that wouldn’t be holding us back.

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Pricing

So the Phenom X3 overclocks fairly well—at least our sample did; your mileage will vary of course. We’re also about to see that it performs fairly well in relation to the rest of AMD’s processor lineup. The company seems most enthusiastic about pricing, though.

The X3 8750 costs $195. The 2.3 GHz 8650 clocks in at $165. And AMD’s entry-level Phenom X3 8450 runs $145.

The Phenom X3s
More Mainstream Offerings From AMD
	Clock Speed	L1 Cache	L2 Cache	L3 Cache	HT Speed	Max TDP	Price
Phenom X3 8750	2.4 GHz	128KB/core	512KB/core	2MB Shared	1.8 GHz	95W	$195
Phenom X3 8650	2.3 GHz	128KB/core	512KB/core	2MB Shared	1.8 GHz	95W	$165
Phenom X3 8450	2.1 GHz	128KB/core	512KB/core	2MB Shared	1.8 GHz	95W	$145
All models based on Rev. B3 silicon

At those prices, you’ll notice a bit of overlap with AMD’s seldom-discussed dual-core lineup. The thinking is that it’d be better to sport three processing cores than the extra frequency afforded by a less complex dual-core chip—at least for the folks who find themselves multi-tasking. The fastest triple-core X3 is also about $15 less than the slowest quad-core X4.

And then there’s the comparison to Intel’s lineup. Intel doesn’t have any three-core CPUs, so we look up to the Core 2 Quad Q6600 as the cheapest quad-core contender (though still more expensive at $224 in quantities of 1,000) and down to the Core 2 Duo E8400 as the most comparable in price (though hardly down, since Intel’s 45nm Wolfdale architecture absolutely screams).

System Setup

AMD Phenom X4 9550 (2.2 GHz)
AMD Phenom X3 8750 (2.4 GHz)
AMD Phenom X3 8650 (2.3 GHz)
AMD Phenom X3 8450 (2.1 GHz)
AMD Athlon X2 4850e (2.5 GHz)
Intel Core 2 Quad Q6600 (2.4 GHz)
Intel Core 2 Duo E8400 (3 GHz)

Gigabyte MA790FX-DQ6 790FX Motherboard
ASUS Striker II Forumula 780i Motherboard

2GB OCZ Technology DDR2-1066 CAS5 Memory (2x1GB)
2GB Corsair DDR2-800 CAS5 Memory (2x1GB)

EVGA e-GeForce 8800 GT Akimbo SC Graphics Card

Seagate Barracuda 7200.11 1TB SATA 3 Gbps Hard Drive

Windows Vista x32, current as of April 17th, 2008 with Windows Update

DirectX 10

Desktop resolution 1600x1200, 32-bit color, 85Hz refresh

We disable Vista’s UAC and generate an image using Norton Ghost 11 to create the same basic benchmark platform for each test bed. The image is frozen with the latest Windows Updates and deployed to each system. The appropriate drivers are then loaded to the machines.

Benchmarks

3DMark06
Unreal Tournament III
Crysis
Lost Planet: Extreme Condition
Half-Life 2: Episode 2
Company of Heroes
Call of Duty 4
PCMark Vantage
Windows Media Encoder

3DMark06

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3DMark06

Notes

It’s Intel all the way in our 3DMark06 Overall result, with the dual-core Core 2 Duo E8400 taking a first place finish. The Core 2 Quad places second. AMD’s offerings fall into place in a somewhat predictable manner, with the quad-core Phenom X4 9550 leading all three Phenom X3s.

The threaded CPU test is another story entirely. Futuremark effectively takes graphics processing out of the picture here, so you aren’t seeing the same interference we’d encounter in a real-world game test at 1600x1200, for example. The quad-core offerings from AMD and Intel shine most brightly, followed by Intel’s Core 2 Duo E8400. Again, the three Phenom X3s trail slightly and are followed by AMD’s 45W Athlon X2 4850e.

Unreal Tournament III

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Unreal Tournament III

Notes

We used the botmatch technique for benchmarking Unreal Tournament, populating our map with 24 characters, 12 to a side.

At 800x600 it’s Intel by a significant margin. To be fair, that Q6600 is quite a bit more expensive than any of the other processors in this evaluation; however, the E8400 is priced much more competitively. All three X3 chips perform comparably. The X4 even manages to file in amongst them.

Benchmarking Unreal Tournament III is about as consistent as tapioca pudding, and we keep running into situation where the scores at 1280x1024 are regularly (and reproducibly) higher than the numbers at 800x600. Thus, the results are even more pronounced at 1280x1024, where Intel CPUs again rule the roost.

Stepping up to 1600x1200 shows up a situation similar to where we were at 800x600. Only now, the quad-core Phenom X4 is stretching its legs a bit to outpace the X3s. We recently had the chance to ask Epic’s Tim Sweeny some questions about how Unreal Tournament uses threading and his answers will be part of an upcoming scaling piece. For now, know that the app is able to fully utilize a quad-core chip’s onboard resources.

Crysis

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Crysis

Notes:

We ditched the baked benchmarks for this test, recorded our own timedemo, and used it instead. Unfortunately, Crysis turns off the AI when you’re playing back demos, so you can expect actual game play to better tax these chips.

Our numbers at 800x600 suggest that we’ll be seeing the same dominance by Intel at higher resolutions. However, the move to 1280x1024 proves otherwise. Intel still takes the top two spots, but AMD’s Phenoms don’t trail very far behind. Things remain close at 1600x1200 with a little anti-aliasing turned on. AMD’s Phenom X3 8750 benefits from a faster clock and the fact that there’s little work for a multi-core processor to do here, taking the lead. The Core 2 Duo chip falls off a bit versus several of the AMD offerings pitted against it, too.

Lost Planet

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Lost Planet: Extreme Condition

Notes:

Both Intel chips take top spots across the board, although by the time you get to settings more gamers would actually use, the competition is really quite narrow. Interestingly enough, the triple-core Phenom X3 inches out AMD’s X4 9550 at all three resolutions.

Half-Life 2

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Half-Life 2: Episode 2

Notes:

Yet again, we see a very tight race up at 1600x1200 with anti-aliasing and anisotropic filtering turned on. And since our setup is able to peg 90+ frames per second, regardless of CPU, it’s a fair bet you’ll be playing at 1600x1200 or greater with a card like NVIDIA’s GeForce 8800 GT.

Stepping back, there’s a lot more variance at 1280x1024 and 800x600, where the Intel processors pull away more noticeably. And once more, the Phenom X3 8750 outpaces AMD’s own Phenom X4 9550 at almost every step of the way.

Company of Heroes

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Company of Heroes

Notes:

The performance picture in Company of Heroes isn’t very exciting until you grab a second graphics card. With just one board in our test beds, both Intel chips enjoy a small lead at 800x600. The advantage shrinks at 1280x1024 and even more at 1600x1200.

Call of Duty 4

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Call of Duty 4: Modern Warfare

Notes

Nothing much new here. It looks like we’re being limited by our graphics card, unfortunately.

PCMark Vantage

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PCMark Vantage

Notes

PCMark Vantage is all about threaded usage models, as it tests some of the most popular applications in a variety of different genres. And yet, the dual-core Core 2 Duo E8400 manages to pull off first-place finishes in half of the suite’s tests. In the other half, it’s the quad-core Core 2 Quad Q6600 claiming the lead.

Overall, AMD’s triple-core Phenom X3 8750 bests the quad-core Phenom X4 9550, though the pair trade blows throughout synthetic testing. The other X3s fall in accordingly, besting the dual-core X2 4850e by a significant margin.

Windows Media Encoder 9

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Windows Media Encoder 9

Notes:

While we’re all about gaming, it’s no secret that the latest titles stifle most attempts to compare processors, especially at the resolutions at which enthusiasts actually play. At 1600x1200, most folks are usually best off spending more money on the fastest video card they can buy.

Power users do more than game, though. Audio and video encoding are much better measures of processor performance. The encoder .dll used in Windows Media Encoder 9 is optimized for up to four threads, making it a great test of the dual- and quad-core chips on the bench. Here’s the interesting part. AMD reported to us that the VC1 encoder included in WME uses one, two, or four cores, so don’t be surprised if the app doesn’t scale as you test. Because our array of chips is so littered with CPUs running at different frequencies and employing different micro-architectures, those words of caution don’t translate. Instead, we see the triple core X3 8750 besting the X4 9550. Even if it is being run as a dual-core chip here, the X3 does quite well.

Perhaps more significant than the actual benchmark result in Windows Media Encoder is the information straight from AMD admitting that not all threaded applications are optimized for an odd number of processing cores. If Windows Media Encoder 9 is defaulting to two threads when it sees three cores, which other programs are doing the same thing? Would this be a case of buying three cores for the price of two or paying for three and getting dual-core performance?

Conclusion

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FiringSquad says:

The story that AMD would like most to tell would be of its platform. And that’s a great story indeed. In this piece, we’ve given the Phenom X3 family as much support as possible in order to get to the processor’s true potential, from an enthusiast motherboard to a $300 graphics card. But that isn’t the configuration most mainstream folks would buy. Instead, they’d be more likely to match a Phenom X3 to a cheaper platform—something like AMD’s 780G.

Now, to its credit, the 780G is quite the piece of work. Less expensive than Intel’s G35 integrated chipset and a heck of a lot more capable in apps that actually use 3D acceleration; the 780G saves AMD’s day here. Plus, you get the option to add a discrete Radeon HD 3450 for $50 bucks and get Hybrid Graphics.

The concept is not without fault. AMD claims that, at a $300 price point, you get the benefits of 780G and a triple-core processor at the price of a dual-core chip. The 780G business is all well and good—I’m all about the platform and am of the opinion that you cannot beat a 780G motherboard for the price. But stepping up to triple-core isn’t exactly free. It costs you clock speed. Add to that a hotfix for Vista enabling support for odd numbers of cores, the need to update SiSoft Sandra for proper operation with triple-core chips, and WME9’s VC-1 encoder that purportedly defaults back to dual-core operation when run on a Phenom X3. It’d seem we need a little more exploration into when that third core is actually being put to use instead.

So it’s not all good news for AMD’s latest attempt at further segmenting the processor market with a three-core design. Nor is it all bad news. Work under the assumption that none of our tests took advantage of a third core (though the synthetics indicate many do)—the Phenom X3 still performed exceptionally and, in many cases, bested the Phenom X4 9550 priced $15 higher. And if a round of hotfixes is needed to add proper triple-core support, consider that the performance picture will only get better.

Think about the overclocking as well. By taking millions of transistors out of the equation, AMD may have opened up a bit of headroom for milking extra frequency out of the Phenom X3. The architecture might not be known for its scalability, but an extra 400 MHz from a mainstream chip isn’t bad at all.

At the end of the day, there’s no getting around the power of Intel’s 45nm Penryn family. The 3 GHz Core 2 Duo E8400, dual-core or not, simply screams. If your inclination is toward the power user side of things, you really must spend the extra few dollars on a Wolfdale-based machine. If, on the other hand, you’re leaning toward an integrated setup with a little Hybrid Graphics action and high-def video playback, Intel simply can’t touch the value of a 780G motherboard paired to a sub-$200 Phenom X3 or Athlon X2.