Meet AMD’s Piledriver-Based FX Line-Up
Ed.: Originally, this story contained a page exploring resonant clock mesh technology, from Cyclos Semiconductor, which was expected to surface in AMD's Piledriver-based SoCs. Upon discussing this in greater depth with the company, however, "the timing of the products and the implementation of resonant clock mesh caused [the technology] to not be productized with "Piledriver" based processors." As such, we've removed that page to avoid any confusion.
As someone who reviews computer hardware, the challenges facing a business matter a lot less to me than the products it sells. We can all agree that the last year was pretty awful for AMD’s processor team, beginning with the power-hungry Bulldozer-based FX CPUs that slowly slid down in price over 12 months in response to a more compelling family of third-gen Core processors from Intel. But every delivery to my SoCal lab represents an opportunity. Chatter about mismanagement, layoffs, and a troubled past matter little in the evaluation of a new CPU. So, let's get down to business.
Sometimes it’s possible to predict the outcome of a story. Had AMD shipped an FX-8170 running 200 MHz faster than its former flagship, I would have guessed that it’d exhibit the same issues with lightly-threaded workloads, it would probably outperform a Core i5-2500K in more intensive tasks, but its power consumption would probably look pretty nasty compared to modern 77 W Ivy Bridge-based chips.
Instead, we have an FX-8350, which centers on the same Piledriver architecture as the Trinity-based APUs introduced less than one month ago. Experience tells us that, per core and per cycle, Piledriver can be as much as 15% faster than a Bulldozer-based design. Add to that the fact that FX-8350 operates at least 400 MHz faster than FX-8150. Oh, yeah. And Ivy Bridge only gave Intel’s line-up single-digit gains. There’s every chance that today’s performance comparison is going to be a lot more interesting than the overwhelmingly negative judgment passed on FX-8150 one year ago.
Meet The Piledriver-Based FX Family
In a faithful return to its Bulldozer approach, AMD sent out the fastest model in its new line-up for review, but is actually introducing eight-, six-, and four-core configurations. Of course, we know they all center on the Piledriver architecture, but the SoC itself is referred to as Vishera, and it’s still branded as FX.
A complete Vishera processor measures 315 square millimeters and is composed of 1.2 billion transistors. Those are the exact same figures given for Zambezi, the previous-generation SoC based on AMD’s Bulldozer architecture. Whatever alterations the architects made—from ISA extensions to a larger L1 DTLB—surface area and transistor count don’t change enough to move the dial on those contextually-irrelevant but interesting-to-know-anyway specifications.
| AMD's 2012 FX Family | |||||||
|---|---|---|---|---|---|---|---|
| Row 0 - Cell 0 | Core Count | Base Clock | Max. Turbo | NB Clock | TDP | Price | OPN |
| FX-8350 | 8C / 8T | 4.0 GHz | 4.2 GHz | 2200 MHz | 125 W | $195 | FD8350FRW8KHK |
| FX-8320 | 8C / 8T | 3.5 GHz | 4.0 GHz | 2200 MHz | 125 W | $169 | FD8320FRW8KHK |
| FX-6300 | 6C / 6T | 3.5 GHz | 4.1 GHz | 2000 MHz | 95 W | $132 | FD6300WMW6KHK |
| FX-4300 | 4C / 4T | 3.8 GHz | 4.0 GHz | 2000 MHz | 95 W | $122 | FD4300WMW4MHK |
Two of the four SKUs boast eight integer cores, or four Piledriver modules, however you choose to label AMD’s compute units. The flagship, FX-8350, features a base clock rate of 4 GHz. Turbo Core technology is able to push that to 4.2 GHz in lightly-threaded workloads, though most of the chip’s speed-up undoubtedly comes from its default state. How much does Turbo Core really do for FX-8350? Not much. In iTunes, our single-threaded benchmark finishes three seconds faster with the feature on.
An FX-8320 drops the base clock rate to 3.5 GHz, though Turbo Core pushes that to 4 GHz under defined thermal limits (a 500 MHz speed-up is likely more meaningful to FX-8320). Both eight-core models include 8 MB of L2 cache (split into one shared 2 MB slice per module) and 8 MB of L3 cache (shared between all four of the SoC’s modules). AMD is suggesting a $195 price tag on FX-8350 and a $169 price on FX-8320.
FX-6300 comes equipped with three active modules (six cores) and drops pricing all the way to $132. A 3.5 GHz base clock rate helps take advantage of the architecture’s strengths in threaded apps, while a 4.1 GHz peak Turbo Core setting tries to compensate for lackluster single-threaded speed. Like the four-module parts, FX-6300 exposes 2 MB of shared L2 per module (totaling 6 MB in this case) and a shared 8 MB L3 cache. Fewer active resources (along with a slightly slower 2 GHz northbridge clock) allow FX-6300 to fit within a 95 W thermal ceiling, down from the 125 W limit imposed by both FX-83x0 processors.
A lone dual-module CPU, FX-4300, is also rated for 95 W. Its base 3.8 GHz clock rate is sped up to 4 GHz in lightly-threaded apps, and a 2 GHz northbridge frequency matches the FX-6300. A drop to 4 MB of shared L3, however, and a price tag just $10 under the triple-module chip will likely encourage most folks to spend the extra $10 bucks.
Although AMD’s architecture doesn’t seem particularly bandwidth-starved, Vishera’s dual-channel DDR3 memory controller officially supports 1866 MT/s data rates. Frankly, we’d rather use lower-latency 1600 MT/s modules to maximize value, particularly since our results show that you don't gain any performance (outside of Sandra 2013 Beta) after spending more on faster memory.
The entire FX line-up also features an unlocked ratio multiplier, which serves to simplify overclocking. Is Vishera scalable enough to make tuning worthwhile? What do you think about 5.125 GHz using a closed-loop liquid cooler?
