AMD isn’t looking to release a new completely new CPU until they have their Zen architecture ready, which should be by the end of the summer at the very latest. In the meantime they’ve been on schedule making small architectural changes to the Bulldozer in order to have their APUs and lower-end CPUs still be competitive. These aren’t large sweeping changes by any means, but what they’ve done with Excavator, the core architecture of the Athlon X4 845 being tested here, are still significant enough to warrant taking a look at the lower-end offerings again.
In fact, though the slight optimizations in the way it’s manufactured has had a profound impact on power savings, leading to a processor that, while it isn’t leaps and bounds above its Steamroller predecessor, at least has a positive increase in performance while lower the power-requirements for the same workload.
Just what changed with the Athlon X4 845 with Excavator underneath?
One of the more significant changes is the switch to a different manufacturing process. It’s still 28nm, but they’ve switched to using a high density library that’s enabled more transistors to be packed into a smaller area. That tech is usually something reserved especially for GPUs, but packing things tighter also allowed for higher voltage tolerances and reduced voltage leaking. That alone makes it a bit more power efficient, up to a quoted 30% even. But the actual performance improvements aren’t many, just a result of the power efficiency targeting that they’ve done with the new libraries and better metal stacking.
Deeper in the architecture they’ve added support for new instructions like AVX2, MOVBE, SMEP and BMI 1 and 2. The L1 cache has been reworked, with an increase in size and some inner prefetch improvements that should lower overall latency. The branch-prediction of Excavator is much better than Steamroller, with a massive 50% increase in size of the Branch Target Buffer and an FPU accelerated cache flush mechanism. All of those small changes amount to around a 15% increase in performance overall compared to a similarly specced Steamroller equipped CPU. That’s not a tremendous amount, but then this is only meant to be a stop-gap until their next-generation CPUs are finally ready.
So, they have a 28nm, 65-watt CPU operating at frequencies that a previous generation 100-watt CPU did. This isn’t meant to be a high-performance CPU and it hasn’t been included in any of the FX processors. This is purely a value-oriented processor, and at around $70, it hits a very sweet spot for the performance it does give. Keep in mind this is competing against lower-tiered Pentiums and Celerons. Thus we look at this processor in that light, as a value-oriented proposition. But how does it actually perform?
Review System Specs
For the purposes of this review I had planned on comparing against the equivalent Intel offering at this price-point, the Pentium G4400, but Intel wasn’t able to loan me one for the purposes of this review, thus it’s only compared against its older sibling, the Athlon X4 860K which operates at a similar frequency. I’ve been able to source the results of the G4400 for a few CPU tests for comparison, however. We also chose to use just one GPU to give an idea of where it performs, not to test outright performance.
- AMD Athlon X4 845/860K
- ASRock FM2A88X-ITX+
- 16GB Kingston HyperX DDR3 2400
- 240GB SanDisk Extreme Pro
- Corsair CS550M
- Gigabyte R7 370
- Windows 10 64-bit
- AMD Drivers 16.5.3