The Bulldozer Review: AMD FX-8150 Tested
by Anand Lal Shimpi on October 12, 2011 1:27 AM ESTPower Management and Real Turbo Core
Like Llano, Bulldozer incorporates significant clock and power gating throughout its design. Power gating allows individual idle cores to be almost completely powered down, opening up headroom for active cores to be throttled up above and beyond their base operating frequency. Intel's calls this dynamic clock speed adjustment Turbo Boost, while AMD refers to it as Turbo Core.
The Phenom II X6 featured a rudimentary version of Turbo Core without any power gating. As a result, Turbo Core was hardly active in those processors and when it was on, it didn't stay active for very long at all.
Bulldozer's Turbo Core is far more robust. While it still uses Llano's digital estimation method of determining power consumption (e.g. the CPU knows ALU operation x consumes y-watts of power), the results should be far more tangible than what we've seen from any high-end AMD processor in the past.
Turbo Core's granularity hasn't changed with the move to Bulldozer however. If half (or fewer) of the processor cores are active, max turbo is allowed. If any more cores are active, a lower turbo frequency can be selected. Those are the only two frequencies available above the base frequency.
AMD doesn't currently have a Turbo Core monitoring utility so we turned to Core Temp to record CPU frequency while running various workloads to measure the impact of Turbo Core on Bulldozer compared to Phenom II X6 and Sandy Bridge.
First let's pick a heavily threaded workload: our x264 HD benchmark. Each run of our x264 test is composed of two passes: a lightly threaded first pass that analyzes the video, and a heavily threaded second pass that performs the actual encode. Our test runs four times before outputting a result. I measured the frequency of Core 0 over the duration of the test.
Let's start with the Phenom II X6 1100T. By default the 1100T should run at 3.3GHz, but with half or fewer cores enabled it can turbo up to 3.7GHz. If Turbo Core is able to work, I'd expect to see some jumps up to 3.7GHz during the lightly threaded passes of our x264 test:
Unfortunately we see nothing of the sort. Turbo Core is pretty much non-functional on the Phenom II X6, at least running this workload. Average clock speed is a meager 3.31GHz, just barely above stock and likely only due to ASUS being aggressive with its clocking.
Now let's look at the FX-8150 with Turbo Core. The base clock here is 3.6GHz, max turbo is 4.2GHz and the intermediate turbo is 3.9GHz:
Ah that's more like it. While the average is only 3.69GHz (+2.5% over stock), we're actually seeing some movement here. This workload in particular is hard on any processor as you'll see from Intel's 2500K below:
The 2500K runs at 3.3GHz by default, but thanks to turbo it averages 3.41GHz for the duration of this test. We even see a couple of jumps to 3.5 and 3.6GHz. Intel's turbo is a bit more consistent than AMD's, but average clock increase is quite similar at 3%.
Now let's look at the best case scenario for turbo: a heavy single threaded application. A single demanding application, even for a brief period of time, is really where these turbo modes can truly shine. Turbo helps launch applications quicker, make windows appear faster and make an easy time of churning through bursty workloads.
We turn to our usual favorite Cinebench 11.5, as it has an excellent single-threaded benchmark built in. Once again we start with the Phenom II X6 1100T:
Turbo Core actually works on the Phenom II X6, albeit for a very short duration. We see a couple of blips up to 3.7GHz but the rest of the time the chip remains at 3.3GHz. Average clock speed is once again, 3.31GHz.
Bulldozer does far better:
Here we see blips up to 4.2GHz and pretty consistent performance at 3.9GHz, exactly what you'd expect. Average clock speed is 3.93GHz, a full 9% above the 3.6GHz base clock of the FX-8150.
Intel's turbo fluctuates much more frequently here, moving between 3.4GHz and 3.6GHz as it runs into TDP limits. The average clock speed remains at 3.5GHz, or a 6% increase over the base. For the first time ever, AMD actually does a better job at scaling frequency via turbo than Intel. While I would like to see more granular turbo options, it's clear that Turbo Core is a real feature in Bulldozer and not the half-hearted attempt we got with Phenom II X6. I measured the performance gains due to Turbo Core across a number of our benchmarks:
Average performance increased by just under 5% across our tests. It's nothing earth shattering, but it's a start. Don't forget how unassuming the first implementations of Turbo Boost were on Intel architectures. I do hope with future generations we may see even more significant gains from Turbo Core on Bulldozer derivatives.
Independent Clock Frequencies
When AMD introduced the original Phenom processor it promised more energy efficient execution by being able to clock each core independently. You could have a heavy workload running on Core 0 at 2.6GHz, while Core 3 ran a lighter thread at 1.6GHz. In practice, we felt Phenom's asynchronous clocking was a burden as the CPU/OS scheduler combination would sometimes take too long to ramp up a core to a higher frequency when needed. The result, at least back then, was that you'd get significantly lower performance in these workloads that shuffled threads from one core to the next. The problem was so bad that AMD abandoned asynchronous clocking altogether in Phenom II.
The feature is back in Bulldozer, and this time AMD believes it will be problem free. The first major change is with Windows 7, core parking should keep some threads from haphazardly dancing around all available cores. The second change is that Bulldozer can ramp frequencies up and down much quicker than the original Phenom ever could. Chalk that up to a side benefit of Turbo Core being a major part of the architecture this time around.
Asynchronous clocking in Bulldozer hasn't proven to be a burden in any of our tests thus far, however I'm reluctant to embrace it as an advantage just yet. At least not until we've had some more experience with the feature under our belts.
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ThaHeretic - Saturday, October 15, 2011 - link
Here's something for a compile test: build the Linux kernel. Something people actually care about.Loki726 - Monday, October 31, 2011 - link
The linux kernel is more or less straight C with a little assembly; it is much easier on a compiler frontend and more likely to stress the backend optimizers and code generators.Chromium is much more representative of a modern C++ codebase. At least, it is more relevant to me.
nyran125 - Saturday, October 15, 2011 - link
Whats the point in having 8 cores, if its not even as fast as an intel 4 core and you get better performance overall with intel.. Heres the BIG reality, the high end 8 core is not that much cheaper than a 2600K. Liek $20-60 MAX> Youd be crazy to buy an 8 core for the same price as an intel 2600K...LIKE MAD!!!
Fiontar - Saturday, October 15, 2011 - link
Well, these numbers are pretty dismal all around. Maybe as the architecture and the process mature, this design will start to shine, but for the first generation, the results are very disappointing.As someone who is running a Phenom II X6 at a non-turbo core 4.0 Ghz, air cooled, I just don't see why I would want to upgrade. If I got lucky and got a BD overclock to 4.6 Ghz, I might get a single digit % increase in performance over my Phenom II X6, which is not worth the cost or effort.
I guess on the plus side, my Phenom II was a good upgrade investment. Unless I'm tempted to upgrade to an Intel set up in the near future, I think I can expect to get another year or two from my Phenom II before I start to see upgrade options that make sense. (I usually wait to upgrade my CPU until I can expect about a 40% increase in performance over my current system at a reasonable price).
I hope AMD is able to remain competitive with NVidia in the GPU space, because they just aren't making it in the CPU space.
BTW, if the BD can reliably be overclocked to to 4.5Ghz+, why are they only selling them at 3.3 Ghz? I'm guessing because the added power requirements then make them look bad on power consumption and performance per watt, which seems to be trumping pure performance as a goal for their CPU releases.
Fiontar - Saturday, October 15, 2011 - link
A big thumbs down to Anand for not posting any of the over-clock benchmarks. He ran them, why not include them in the review?With the BD running at an air cooled 4.5 Ghz, or a water cooled 5.0 Ghz, both a significant boost over the default clock speed, the OC benchmarks are more important to a lot of enthusiasts than the base numbers. In the article you say you ran the benchmarks on the OC part, why didn't you include them in your charts? Or at least some details in the section of the article on the Over-clock? You tell us how high you managed to over-clock the BD and under what conditions, but you gave us zero input on the payoff!
Oscarcharliezulu - Saturday, October 15, 2011 - link
...was going to upgrade my old amd3 system to a BD, just a dev box, but I think a phenom x6 or 955 will be just fine. Bit sad too.nhenk--1 - Sunday, October 16, 2011 - link
I think Anand hit the nail on the head mentioning that clock frequency is the major limitation of this chip. AMD even stated that they were targeting a 30% frequency boost. A 30% frequency increase over a 3.2 GHz Phenom II (AM3 launch frequency i think) would be 4.2 GHz, 17% faster than the 3.6 GHz 8150.If AMD really did make this chip to scale linearly to frequency increases, and you add 17% performance to any of the benchmarks, BD would roughly match the i7. This was probably the initial intention at AMD. Instead the gigantic die, and limitations of 32nm geometries shot heat and power through the roof, and that extra 17% is simply out of reach.
I am an AMD fan, but at this point we have to accept that we (consumers) are not a priority. AMD has been bleeding share in the server space where margins are high, and where this chip will probably do quite well. We bashed Barcelona at release too (I was still dumb enough to buy one), but it was a relative success in the server market.
AMD needs to secure its spot in the server space if it wants to survive long term. 5 years from now we will all be connecting to iCloud with our ARM powered Macbook Vapor thin client laptops, and a server will do all of the processing for us. I will probably shed a tear when that happens, I like building PCs. Maybe I'll start building my own dedicated servers.
The review looked fair to me, seems like Anand is trying very hard to be objective.
neotiger - Monday, October 17, 2011 - link
"server space where margins are high, and where this chip will probably do quite well."I don't see how Bulldozer could possibly do well in the server space. Did you see the numbers on power consumption? Yikes.
For servers power consumption is far more important than it is in the consumer space. And BD draws about TWICE as much power as Sandy Bridge does while performs worse.
BD is going to fail worse in the server space than it will in the consumer space.
silverblue - Monday, October 17, 2011 - link
I'm not sure that I agree.For a start, you're far more likely to see heavily threaded workloads on servers than in the consumer space. Bulldozer does far better here than with lightly threaded workloads and even the 8150 often exceeds the i7-2600K under such conditions, so the potential is there for it to be a monster in the server space. Secondly, if Interlagos noticably improves performance over Magny Cours then coupled with the fact that you only need the Interlagos CPU to pop into your G34 system means this should be an upgrade. Finally, power consumption is only really an issue with Bulldozer when you're overclocking. Sure, Zambezi is a hungrier chip, but remember that it's got a hell of a lot more cache and execution hardware under the bonnet. Under the right circumstances, it should crush Thuban, though admittedly we expected more than just "under the right circumstances".
I know very little about servers (obviously), however I am looking forward to Johan's review; it'd be good to see this thing perform to its strengths.
neotiger - Monday, October 17, 2011 - link
First, in the server space BD isn't competing with i7-2600K. You have to remember that all the current Sandy Bridge i7 waste a big chunk of silicon real estate on GPU, which is useless in servers. In 3 weeks Intel is releasing the 6 core version of SB, essentially take the transistors that have been used for GPU and turn them into 2 extra cores.Even in highly threaded workloads 8150 performs more or less the same level as i7-2600K. In 3 weeks SB will increase threaded performance by 50% (going from 4 cores to 6). Once again the performance gap between SB and BD will be huge, in both single-threaded and multi-threaded workloads.
Second, BD draws much higher power than SB even in stock frequency. This is born out by the benchmark data in the article.