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AMD's Phenom X4 9750 and 9850 processors

Let's try this again
— 12:11 AM on March 27, 2008

Most of you are aware by now of the problems with AMD's quad-core Phenom processors. As we have chronicled closely, the chips were late to market and debuted with unexpectedly low clock frequencies. As a result, their performance was underwhelming compared to Intel's Core 2 offerings. Worse yet, shortly before its release, AMD discovered a bug in the Phenom that could cause a system hang in certain, very specific circumstances. This so called "TLB erratum" caused AMD to cease shipments of the Phenom's server-oriented counterpart, the Opteron 2300 series, but the firm went ahead with its plans to sell Phenoms in consumer PCs. For those systems, AMD offered a workaround in the form of a BIOS update, but the cure was arguably worse than the affliction, causing substantial performance hit in many applications.

During our coverage of the unfolding TLB erratum story, AMD told us it planned to deliver a new revision of its quad-core silicon in "mid-to-late Q1" of this year. This revision, dubbed B3, would include a proper chip-level fix for the TLB erratum. Since then, we've been waiting impatiently for these new chips to arrive while agitating for AMD to provide consumers with more information about whether and how they might disable the TLB workaround on existing Phenoms.

Fortunately, today, the wait appears to be over. Like a tired cliché rising from the keyboard of a website author, the Phenom has been resurrected in the form of silicon revision B3. Accordingly, AMD is announcing a whole new lineup of Phenom processors that should be available for purchase almost immediately. Even better, AMD seems to have found some additional clock frequency headroom in the B3 chips, so that lineup extends to new territory in the form of the Phenom X4 9750 and 9850 Black Edition processors.

New Phenoms: It's all about the Xs
As expected, AMD's new Phenom lineup includes a number of "xx50" model numbers intended to denote the presence of B3 silicon and a proper hardware fix for the TLB erratum. For instance, the Phenom 9550 replaces the Phenom 9500. Aside from the silicon rev and the TLB fix, the two products are essentially the same: both have four cores, a 2.2GHz core clock, 2MB of L3 cache, and all the rest. Of course, the Phenom 9550 should be faster in a default configuration because it doesn't suffer the performance penalty caused by the TLB workaround.

The new Phenom line includes a number of surprises, though. Here's a look at the whole list, with vitals for each model.

Model Clock speed North bridge
Cores TDP Price OEM only Rev. B3
Phenom X3 8400 2.1GHz 1.8GHz 3 95W ~$150 x
Phenom X3 8600 2.3GHz 1.8GHz 3 95W ~$175 x
Phenom X4 9100e 1.8GHz 1.6GHz 4 65W ~$200 x
Phenom X4 9550 2.2GHz 1.8GHz 4 95W $195 x
Phenom X4 9650 2.3GHz 1.8GHz 4 95W - x x
Phenom X4 9750 2.4GHz 1.8GHz 4 95W - x x
Phenom X4 9750 2.4GHz 1.8GHz 4 125W $215 x
Phenom X4 9850 Black Edition 2.5GHz 2.0GHz 4 125W $235 x

Perhaps the biggest surprise for the pedantic little man inside of 98.2% of geeks is the addition of "X3" and "X4" indicators in the new Phenom model names, whose numbers correspond to the number of active processing cores on each chip. This naming scheme harkens back to the Athlon 64 X2, of course. We saw the "Phenom X4" name bandied about prior to the Phenom's initial release, but then AMD canned it and went with straight model numbers. Apparently, that didn't take. AMD says its customers liked the Xs, and so they're back—this time, presumably, for good.

Once you're over the shock of that nomenclature recalibration, you'll probably notice the "X3" Phenoms in the list. Yep, these are the vaunted triple-core variants of the Phenom we've expected for some time; they're official now, but only for large PC makers known as original equipment manufacturers (OEMs). Over half the new Phenom lineup is intended only for OEMs, in fact, and that's why we have only approximate prices listed for those processors, if we have them at all. The big dawgs get all sorts of interesting stuff, including the tri-core chips, a low-power variant of the Phenom with a 65W thermal/power envelope (or TDP), and a Phenom X4 9750 with a 95W TDP. We can expect to see consumer versions of these products eventually; those should all be B3 silicon when they arrive.

AMD saved some of the fun for the rest of us, though. It claims the Phenom X4 9550 is the lowest-priced quad-core CPU on the market at under $200, and the 9750 at 2.4GHz doesn't look like a bad deal, either. The most intriguing product of the lot, however, is the Phenom X4 9850 Black Edition. This puppy comes with a 2.5GHz core clock and a 2GHz north bridge clock—important because the north bridge clock governs the speed of the L3 cache. That should make the 9850 a little bit quicker than it might otherwise be. Like AMD's other "Black Edition" processors, the 9850 has an unlocked upper clock multiplier that makes overclocking ridiculously, guilt-inducingly easy. And although it's AMD's flagship model, the 9850 lists for only $235, well below the list prices for ostensible competitors like the Core 2 Quad Q6600. This combination of attributes should make the 9850 the one to have, in my view.

Keeping tabs on the competition
The new Phenoms have the fortune of making it to market just as Intel is struggling to meet demand for its new 45nm chips, which means the Phenoms face a slightly less lethal mix of competitors.

For instance, this review is our first look at Intel's new 45nm Core 2 Duo E8400 and E8500 processors. Although they have only two cores to the Phenom's four, those two cores run at 3GHz and 3.16GHz frequencies, with (roughly) up to 20% higher clock-for-clock performance than the 65nm version of the Core 2 Duo. As a result, they're able to give the lower frequency Phenoms a run for their money, even in widely multithreaded applications. But, as we've noted, the availability of these processors at online vendors is rather spotty, and prices have risen where they are available. The E8500's ostensible $266 list price is already higher than the Phenom X4 9850's, too.

The Phenom will face even deadlier competition in the form of Intel's new 45nm Core 2 Quad processors, but those are even harder to find right now. We pinged Intel about those CPUs in preparation for this review, and the company says all of the new 45nm Core 2 Duo and Quad processors are indeed shipping now—including the Core 2 Quad Q9450, Q9550, and the Core 2 Extreme QX9770, interestingly enough. We weren't able to get any specific ETA for when the availability picture should improve, but Intel says it expects supplies to rise to meet demand as 45nm production ramps up.

One of the more notable developments in Intel's 45nm lineup, incidentally, is the recent and very quiet introduction of the Core 2 Quad Q9300. The Q9300 runs at 2.5GHz and, like the other 45nm Core 2 Quads, has a 1333MHz front-side bus. However, the Q9300 has only half the L2 cache—6MB total—of its siblings and looks tailor-made to take on the new Phenoms. We'll try to get our hands on a Q9300 to test soon, along with other speed grades of the 45nm Core 2 Quads.