It’s been a rocky year for AMD. In retrospect, Bulldozer’s disappointing performance was the tip of the proverbial iceberg. Since it launched, Sunnyvale has laid off thousands, is preparing to lay off thousands more, cancelled its first set of 28nm chips based on the Bobcat architecture, and has lost ground overall in the PC market. Multiple executives have fled the company, margins have tumbled, and long-term prospects are dim, at best.

In the midst of all this chaos, AMD’s engineers have plugged away at refining Bulldozer. The first APU based on Piledriver, codenamed Trinity, debuted last spring; the desktop variant hit shelves at the beginning of this month. Today, AMD is rolling out the Piledriver core to Socket AM3+ motherboards as well. These new chips, codenamed Vishera, are supposed to deliver a bevy of improvements that address some of Bulldozer’s weakest areas.

Rather than running Vishera through a broad range of consumer tests, we’ve focused on a few benchmarks designed to highlight the low-level differences between Vishera, Bulldozer, and Thuban as well as Intel’s Ivy and Sandy Bridge. Does Piledriver fix ‘Dozer, or at least significantly improve its value proposition? Let’s find out.

Note: AMD’s Turbo Core and Intel’s Turbo Mode were disabled on all chips, in order to prevent them from adjusting the CPU’s clock speed and throwing off results. As a consequence, the results here will be lower than in a standard review, particularly for single-thread performance.

What Piledriver needs to do

We’ve discussed Piledriver’s features and improvements over Bulldozer at some length and recommend consulting those stories if you want in-depth information on how Piledriver improves on BD. There are three key areas where Piledriver must improve on Bulldozer in order for AMD to win back the ground it’s lost to Intel.

Single-threadperformance: Bulldozer’s single-thread performance was significantly lower than AMD’s previous generation CPU, codenamed Thuban. This fact, combined with the core’s inability to hit its target clock speeds, fundamentally crippled the processor. The FX-8350 attacks one of these problems off the bat, the chip’s base clock is 11% faster than the 8150’s, and its Turbo Mode pushes four cores up to 4.2GHz (the 8150 topped out at 3.9GHz when four or more cores were active).

Power consumption: Bulldozer, like the original Phenom, was a power hog. This had direct consequences for the chip’s ability to scale. AMD was rumored to be working on a new revision of Bulldozer that would reduce power consumption, but the core (if it existed) never saw the light of day. Bringing the chip’s TDP into line is essential to gaining design wins in smaller form factors.

Multi-core scaling: When AMD created Bulldozer, it promised that it could offer strong scaling while sharing core resources. In practice, Bulldozer’s scaling was ~80% that of a traditional dual-core design. This wasn’t an outrageous penalty, given how much die space AMD had saved, but it further hurt the chip in comparisons against Thuban. Eight BD cores at 80% of Thuban scaling often looked a heck of a lot like six Thuban cores.

The chip

On a high level, Vishera looks just like Bulldozer. Its caches are all the same size, the same set associativity, and the same functions are shared at the core/module level. AMD hasn’t disclosed the die size, but the transistor count is the same, at 1.2B. Given this, we’re assuming that the two chips are similarly sized, at 315 mm sq. All these similarities make it easy to compare TDPs and clock speeds between the new parts and the old:

One thing we can conclude off the bat — Vishera delivers some of the clock speed Bulldozer promised. Exact figures vary — the FX-8320 is 12-17% faster than the FX-8120, while the FX-6300 and FX-6120 hit exactly the same clock speeds and TDP. Still, there’s solid gains on the clock speed front virtually across the board.

Another thing that’s changed in 12 months is the CPU’s launch price. When AMD launched Bulldozer, it priced the chip at ~$270. Given its lackluster performance versus the $180 X6 1100T and the drubbing it took from Intel CPUs in the same price bracket, the FX-8150 was a poor, poor value. This time around, AMD has priced the top-end FX-8350 at $195. Whacking nearly 30% off the launch price changes the points of comparison. This time, AMD is claiming that the FX-8350 is a strong match for Intel’s Core i5-3550 CPU — and that’s the Ivy Bridge we chose for our own tests. The Core i5-3550 is a quad-core CPU at 3.3GHz with a 3.7GHz Turbo Mode. Hyper-Threading is not enabled on this processor.

Both AMD CPUs were tested on an Asus Crosshair V using the latest BIOS, 8GB of DDR3-1600, and a Radeon 7950 GPU. Windows 7 SP1 (64-bit) was installed, along with all additional MS updates and the two scheduler patches Microsoft released for Bulldozer last year.

Next page: Benchmarks