We have to admit that the first encounter with Bulldozer was a bit disappointing, whether we’re talking about our own or the general impression. Simply enough, AMD’s octa-core CPU was expected to deliver a lot, yet it was nowhere near the best that the opposing team had to offer. Due to its architecture, which groups one integer and two FPU units, this CPU favours well-optimised multi-threaded applications.
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Unfortunately, performance in single-threaded applications was sub-par compared to what the competition had to offer. Interestingly enough, even AMD’s CEO came out with a statement saying that the company has forfeited the race for the #1 spot in terms of performance. After we got accustomed to the fact that AMD will no longer attempt to chase Intel in the high-end segment, things fell into place. The prices of Bulldozer CPUs are such that all positioning is done according to performance of competing models from Intel’s Core series. Still, the company desperately needed a boost to try and keep up with the competition, even if only in this way. The solution was a new, refreshed series of FX CPUs, with new cores, codenamed Piledriver. We deliberately say “refreshed” because AMD hasn’t changed the technology a great deal, in spite of many users hoping for the opposite. As much as anyone may hope for that, thorough changes to the architecture never happen overnight, and not even the biggest of companies (which AMD certainly is) can rectify their errors in a short period of time. That said, AMD still sticks to the Bulldozer base, which is quite logical.

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The CPU that we got for testing carries the name FX-8350 and is intended to replace the current FX-8150 model. The fact that no obvious changes are to be seen in the specs contributes to the aforementioned story. Both chips have a surface of 316 mm² and consist of 1.2 billion transistors. The same goes for many other features. Both octa-core models are made in 32 nm lithography, with 1 MB of L2 cache per FPU and a shared L3 cache of 8 MB. The layout scheme is also nearly identical. Still, there are subtle changes to be found, such as the improved branch prediction and scheduler. Hardware prefetch has become more efficient, and the same goes for L2 cache. All these changes impact the performance of a CPU, and with the physical limitations in mind, it can be said that the changes and optimisations are impressive. It should also be noted that AMD has introduced support for FMA3 and F16C (CVT16) with the latest generation. These are instruction sets for x86 architecture which bring support for 128- and 256-bit instructions for fused multiply-add functions (FMA). But how exactly do all these tiny improvements add up in practice? The seemingly long list of changes is dwarfed by the fact that the schemes and specs of these two CPUs are essentially the same. With that question in mind, we set out to see just how faster FX-8350 is compared to the old FX-8150.

  AMD FX-8150 AMD FX-8350
Core code name Zambezi Vishera
Frequency speed (Turbo core) 3.,6 (4.,2) GHz 4.,0 (4.,2) GHz
Memory controller 2x 64-bit 1866 MHz DDR3
L1 instruction cache 64 KB L1-I per module (shared with 2 cores)
L1 Data cache 2x 16 KB L1-D per module (16 KB L1-D per core)
L2 cache 2048 KB per module
L3 cache 8192 KB L3
Total cache memory 4x 2 MB L2 + 8 MB L3
Production process 32 nm HighK Metal Gate SOI
Declared TDP 125 W
No. cores / threads / modules 8 / 8 / 4
Socket Socket AM3+
Price $190 $220

Fair and square

It’s clear that FX-8350 has a single blatant advantage over FX-8150 – the clock, which has been upped by an increased multiplier. While FX-8150 “ticks” at a default of 3600 MHz, the newer model rounds it up at 4 GHz. Therefore, it isn’t difficult to presume that FX-8350 will be faster even without any changes to the CPU itself. Furthermore, native support to 1866 MHz RAM when all four modules are used will make the new model even better in certain scenarios. However, in order to provide realistic conditions and see just how much the architecture has advanced, we had to establish certain rules. Firstly, we decided to even out the clocks and overclocked the older model to 4 GHz. This was done directly by changing the multiplier, so as to leave all the other settings untouched. Furthermore, the memory clock was set to 1600 MHz for both models, as this is the most common setting in the PCs of today and ensures that neither of the two models can take away the victory by taking a shortcut. Finally, to measure just how better FX-8350 is than FX-8150 as a concrete product, we ran all tests on the latter’s default settings as well. This gave us two clear lines of deduction – how much difference there is between the two architectures, and the same comparison between the two models as such. Interesting? Definitely.

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The results

Firstly, let’s deal with tests that compare the two CPUs in the same conditions, i.e. when working at exactly the same clocks. The first thing one can notice is that differences are definitely there, despite identical specifications, with the exception of memory performance, which was supposed to remain identical anyway. AIDA benchmark isn’t entirely precise in terms of measuring performance, and can vary by as much as 5% between measurements. Since the difference between the two models has varied between -10% and 10%, it’s clear that the controller has obviously been left untouched. This is the only test that has failed to yield significant differences, though. All other tests clearly show that FX-8350 brings improvements on the architectural level. Well-optimised software favours the new model most. The best examples thereof are x264 benchmark and Blender, both of which gave way to Piledriver cores by as much as 10% at identical clocks. Furthermore, 3DMark also gave a visible advantage to AMD’s new CPU, awarding it with a boost of 10%. However, no clear differences can be seen in ill-optimised applications that execute on a single core. Cinebench was the first one to show that in its single-core test. If you add the fact that FX-8350’s nominal clock is higher by 200 MHz, the performance hike is definitely noticeable, which is especially important if you’re not an overclocker by nature and don’t feel like meddling with the speed of your CPU. In that case, you’ll be glad to know that FX-8350 is up to 20% faster than its predecessor.

Test results    
  AMD FX-8350 @ 4GHz AMD FX-8150 @ 3.6GHz AMD FX-8150 @ 4GHz FX-8350 vs FX-8150 @3.6 / 4GHz
3DMark 11 Performance Physics 7286 6315 6588 +15.3% / +10.6%
PC Mark 7 Final Score 4521 4204 4174 +7.5% / +8.3%
Aida64 Extreme 2.50  
Memory read/write/copy [MB/s] 13307 / 11031 / 15659 12256 / 10205 / 17148 12149 / 10207 / 16575 from -10 to +10%
Memory latency [ns] ** 56.1 55.8 57.4 <1%
7-Zip 7.20 x64 comp./decomp. [kB/s] 19002 / 264507 16904 / 230669 17872 / 247632 +14.5% / +6.7 %
x264 HD Benchmark 5.0 encoding [fps] 54.5 / 14.9 50.5 / 12.9 51.4 / 14.1 +15.5% / 5.7%
Blender x64 [sec] ** 197.2 234.1 217.2 +18.7 / +10.1%
Cinebench R11.5  
CPU  1.08 1.03 1.04 +4.8% / +3.8%
CPU Single Core 6.91 5.97 6.55 +15.7% / +5.5%
OpenGL 68.78 59.19 65.42 +16.2% / +5.1%
True Crypt 7.1  
AES [GB/s] 3.6 3.3 3.5 +9.1% / +2.8%
Twofish [MB/s] 756 646 706 +17.1% / +7.1%
Serpent [GB/s] 432 382 413 +13% / +4.6%
** less is better
Test config: ASUS Sabertooth 990FX R2.0, Kingston 2x 2 GB HyperX DDR3 2133 MHz, AMD Radeon HD7850 1 GB, Windows 7 64-bit Ultimate 

Fair enough

AMD has stated that Vishera CPUs will be up to 20% faster than Zambezi models. After our thorough testing, it’s clear that this wasn’t just marketing hype, but the factual state of affairs. Is Vishera the turning point which will bring AMD back to the throne? Not at all, but the performance increase is sufficient to claim advancement and keep moving on. AMD definitely needed a move such as this to remain in the game, while their engineers tentatively keep working on an entirely new architecture. The good news for Bulldozer owners is that they don’t have to think about upgrading their CPUs, and we strongly recommend them to wait for the next generation. However, those who were planning to base their new PC on one of the FX CPUs should definitely wait a bit and get their hands on one of the new models, as the old ones are slated to be replaced with identically-priced new ones. An extra performance boost of 5-20% will reflect on all possible tasks, whether you care about video encoding, gaming or something else. That said, all of you who were striving for a Bulldozer should definitely focus on Vishera and the new FX or Trinity models based on Piledriver cores.