AMD's Phenom quad-core processor had a rough launch. It was late, had lower clock speeds than expected, and was slower than Intel's quad-core chips. And just as the chips hit the market, an erratum (error) was discovered in the chip that could cause lock-ups in rare multitasking situations, requiring a BIOS patch that slowed down the chip 10 percent or more.
Now AMD is back with its second-generation, errata-free Phenom X4 chips, which can run at their full potential. At the top of the line is the Phenom X4 9850 Black Edition. The Black Edition moniker signifies that the chip has an unlocked multiplier, offering more flexibility for overclocking. At stock speeds, this quad-core chip runs at 2.5GHz, with 2GHz Hypertransport and memory clocks (compared to 1.8GHz for lower-end Phenom X4s). Along with the 9850, AMD has also introduced the $215 2.4GHz Phenom X4 9750 and the $195 2.2GHz Phenom X4 9550.
These 50-series processors aren't radically different from the first-generation Phenom chips. Clock-for-clock, their performance matches the earlier chips they replace, but without the erratum patch slowdown. The Phenom X4 2.5GHz 9850 gets a slight speed boost over the formerly high-end 2.4GHz 9700, and adds the unlocked multiplier.
The Phenom now runs apps up to 25 percent faster than an Athlon X2 at the same clock rate. Speedup is even greater with multicore-aware programs such as video editors and some games. The Phenom X4 is a true quad-core chip, with four independent cores on a single die; AMD also plans a triple-core Phenom X3 series. Unlike the Athlon X2, the memory controller can run at an independent clock rate. Newer Socket AM2+ motherboards let you install fast 1,066MHz memory or overclock your RAM in a Phenom system without changing the CPU's operating speed.
Though AMD has added new SSE4a multimedia instructions, these aren't entirely compatible with the SSE4.1 instructions used on Intel's newer Core 2 processors, so programs will need to add specific support for them. DivX 6.8, for instance, takes advantage of SSE4.1 on the newest Core 2 CPUs, but defaults to the older SSE2 instructions when running on a Phenom.
Despite the unlocked multiplier, don't necessarily expect to pop into your BIOS and boost the chip's speed dramatically. The 50-series Phenom X4 chips are still built on a 65-nanometer (nm) process (compared to the smaller 45nm method used by the newest Intel chips), and due to heat and power issues, aren't likely to have a lot of overclocking headroom. We were able to overclock our 9850 easily to 2.7GHz with no voltage changes, but the system locked up at 3GHz even with a slight voltage boost. Higher clock rates might be achievable with additional trial and error, but don't expect the Phenom X4 to be a great overclocker. AMD does provide the helpful Overdrive utility, which lets you experiment by setting a wide variety of CPU settings directly from Windows.
Performance from the Phenom X4 9850 was much improved over that of the Phenom 9600 we tested last year. It still lagged behind Intel's similarly priced Core 2 Quad Q6600 chip, but the numbers were much closer than before. The Phenom X4 9850 finished our quad-core Sony Vegas 8 Professional rendering test in 4 minutes and 22 seconds. That's slower than the 3 minutes and 57 seconds achieved by the Q6600, but dramatically faster than the Phenom 9600's 7 minutes and 2 seconds. The iTunes recompression test finished in 7 minutes and 35 seconds, lagging behind the Q6600's 6 minutes and 2 seconds, but nearly a minute faster than the Phenom 9600's 8 minutes and 34 seconds.
The Phenom X4 chips still can't catch Intel in a pure speed race. If you need the fastest-possible computer for gaming, video editing, or other processor-intensive tasks, the Phenom X4 isn't going to be your top choice. If you're looking to build a budget system that still offers good performance for everyday computing chores, however, the Phenom X4 is an excellent multitasker. And if you're currently using an Athlon X2 processor on a Phenom-compatible motherboard, upgrading to a Phenom X4 is a no-brainer—it'll give you a noticeable performance boost in most apps, and a dramatic speedup in programs that can use take advantage of all four cores.
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