The Bulldozer Review: AMD FX-8150 Tested
by Anand Lal Shimpi on October 12, 2011 1:27 AM ESTThe Pursuit of Clock Speed
Thus far I have pointed out that a number of resources in Bulldozer have gone down in number compared to their abundance in AMD's Phenom II architecture. Many of these tradeoffs were made in order to keep die size in check while adding new features (e.g. wider front end, larger queues/data structures, new instruction support). Everywhere from the Bulldozer front-end through the execution clusters, AMD's opportunity to increase performance depends on both efficiency and clock speed. Bulldozer has to make better use of its resources than Phenom II as well as run at higher frequencies to outperform its predecessor. As a result, a major target for Bulldozer was to be able to scale to higher clock speeds.
AMD's architects called this pursuit a low gate count per pipeline stage design. By reducing the number of gates per pipeline stage, you reduce the time spent in each stage and can increase the overall frequency of the processor. If this sounds familiar, it's because Intel used similar logic in the creation of the Pentium 4.
Where Bulldozer is different is AMD insists the design didn't aggressively pursue frequency like the P4, but rather aggressively pursued gate count reduction per stage. According to AMD, the former results in power problems while the latter is more manageable.
AMD's target for Bulldozer was a 30% higher frequency than the previous generation architecture. Unfortunately that's a fairly vague statement and I couldn't get AMD to commit to anything more pronounced, but if we look at the top-end Phenom II X6 at 3.3GHz a 30% increase in frequency would put Bulldozer at 4.3GHz.
Unfortunately 4.3GHz isn't what the top-end AMD FX CPU ships at. The best we'll get at launch is 3.6GHz, a meager 9% increase over the outgoing architecture. Turbo Core does get AMD close to those initial frequency targets, however the turbo frequencies are only typically seen for very short periods of time.
As you may remember from the Pentium 4 days, a significantly deeper pipeline can bring with it significant penalties. We have two prior examples of architectures that increased pipeline length over their predecessors: Willamette and Prescott.
Willamette doubled the pipeline length of the P6 and it was due to make up for it by the corresponding increase in clock frequency. If you do less per clock cycle, you need to throw more clock cycles at the problem to have a neutral impact on performance. Although Willamette ran at higher clock speeds than the outgoing P6 architecture, the increase in frequency was gated by process technology. It wasn't until Northwood arrived that Intel could hit the clock speeds required to truly put distance between its newest and older architectures.
Prescott lengthened the pipeline once more, this time quite significantly. Much to our surprise however, thanks to a lot of clever work on the architecture side Intel was able to keep average instructions executed per clock constant while increasing the length of the pipe. This enabled Prescott to hit higher frequencies and deliver more performance at the same time, without starting at an inherent disadvantage. Where Prescott did fall short however was in the power consumption department. Running at extremely high frequencies required very high voltages and as a result, power consumption skyrocketed.
AMD's goal with Bulldozer was to have IPC remain constant compared to its predecessor, while increasing frequency, similar to Prescott. If IPC can remain constant, any frequency increases will translate into performance advantages. AMD attempted to do this through a wider front end, larger data structures within the chip and a wider execution path through each core. In many senses it succeeded, however single threaded performance still took a hit compared to Phenom II:
At the same clock speed, Phenom II is almost 7% faster per core than Bulldozer according to our Cinebench results. This takes into account all of the aforementioned IPC improvements. Despite AMD's efforts, IPC went down.
A slight reduction in IPC however is easily made up for by an increase in operating frequency. Unfortunately, it doesn't appear that AMD was able to hit the clock targets it needed for Bulldozer this time around.
We've recently reported on Global Foundries' issues with 32nm yields. I can't help but wonder if the same type of issues that are impacting Llano today are also holding Bulldozer back.
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Iketh - Thursday, October 13, 2011 - link
I play FSX and Starcraft 2... both require copious processing power.And I just built an i7-2600K system with a radeon 6870 and blu ray writer for.... $960
paultaylor - Thursday, October 13, 2011 - link
While the benchmarks are very revealing of the "ahead of its time" nature of Bulldozer, I think AMD should've kicked off by focusing on server applications instead of desktop ones.Considering what I've seen so far I think some additional benchmarks on threading/scaling would come in handy – it would actually show the true nature of BD as, right now, it’s behaving like a quad-core processor (due to the shared nature of its architecture, I presume) in most cases, rather than an octacore. Charting that out might be very revealing. The situation now looks like Intel's 2nd (3rd?) generation hyperthreading quad-cores provide more efficient multithreading than 8 physical cores on an AMD FX.
Don’t get me wrong, we’ve heard from the beginning that BD will be optimised for server roles, but then we’re outside the feedback loop. Shouldn’t someone inside AMD be minding the store and making sure the lower shelves are also stocked with something we want?
A longer pipeline and the old “we’ll make it up in MHz” line reeks of Netburst, unfortunately, and we all know how that ended. Looking at the tranny count, it’s got almost twice as many as the Gulftown, with 27% bigger die size for the entire CPU… which will mean poorer yields and higher costs for AMD, not to mention that either the fabbing process is really being tweaked or the speed bumps will not come at all, as the TDP is already high-ish. Ironically it reminds me of Fermi. Speaking of which… BD may become the punchline of many jokes like “What do you get when you cross a Pentium 4 and a Fermi?”
On the other hand it seems AMD has managed one small miracle, their roadmaps will become more predictable (a good thing from a business perspective) and that will exert a positive influence with system integrators. Planning products ahead of the game, in particular in this 12-month cycle, might do some good for AMD, if they survive the overal skepticism that BD is currently "enjoying".
Other than that, another fine unbiased article.
rickcain2320 - Thursday, October 13, 2011 - link
Bulldozer/Zambezi seems to look more like a server CPU repackaged as a consumer grade one. Excellent in heavily threaded apps, not so hot in single threads.One CPU that is promised but isn't here is the FX-4170. I would have liked to see some benchmarks on it.
gvaley - Thursday, October 13, 2011 - link
We all get that. The problem is, with this power consumption, it can't make it into the server space either.kevith - Thursday, October 13, 2011 - link
Having waited so long for this, it´s a bit disappointing, when I compare price/performance.I went from C2D E 7300 acouple of years ago, and changed setup to Athlon II x2 250, and the performance difference made me regret right away.
And now, I have to change my MB and memory to DDR3 no matter what I choose, Intel or AMD. So I´ve looked forward to this release.
And it makes my choice very easy: I´l go back to Intel, no more AMD for me on the CPU side. And Ivy Bridge is coming, and will definetely smoke AMD.
Which is sad, it would have been nice with some competition.
eccl1213 - Thursday, October 13, 2011 - link
Earlier this week most sites reported that the FX and BD based Opteron 4200 and 6200 where both being released on Oct 12th.But I haven't found a single review site with interlagos benchmarks.
Have those parts been further delayed? We know revenue shipment happened a while back but I'm not seeing any mention of them in the wild yet.
xtreme762 - Thursday, October 13, 2011 - link
I haven't bought an Intel chip since 1997. But with this BS bulldozer launch, that is now going to change! amd should be ashamed of themselves. I for one will now sell all of my amd stock and purchase Intel. I will probably only end up with a few shares, but at this point, I cannot see supporting liars and fakes. And I will NEVER buy an amd product again, not a video card, cpu, mobo, not nothing! What a disappointment amd is.....All the amd crap I have will be tossed in the trash. I'm not even going to bother trying to sell it. WooHoo amd made a world record OC with a cpu not worth it's weight in dog poo!
connor4312 - Thursday, October 13, 2011 - link
Very interesting review. I'd be interested to see Bulldozer's benchmarks when it's overclocked, which, if I am correct, is higher than any Intel CPU can go. AMD seems to have made a turnaround in this aspect - Intel CPUs were historically more overclock-able.Suntan - Thursday, October 13, 2011 - link
As always, a very detailed review. But what about the capability of the "value" chips? Namely, is it worth it to spend around $100 to replace an Anthlon X4 with an FX4100?There are a number of us that picked up the X4 a couple years back for its low cost ability to encode and do general NLE editing of video. Is it worthwhile to replace that chip with the FX4100 in our AM3+ mobos? And what kind of improvements will there be?
As you rightly stated, a lot of us are attracted to AMD for their bang-for-buck. Just because the industry as a whole wants to bump up prices endlessly, there are still a lot of us that like to see good comparisons of the performance of CPUs available for around 1 Benjamin.
-Suntan
Pipperox - Thursday, October 13, 2011 - link
Frankly, it seems to me the disappointment of AMD fans to be quite excessive.Worst CPU ever?
What was then Barcelona, which couldn't compete with Core 2?
Bulldozer, set aside old single threaded applications, is slotting between a Core i5 2500 and Core i7 2600K.
Which other AMD CPU outperforms in any single benchmark a Core i7 2600k?
A higher clocked Thuban with 2 extra cores would have been hotter and more expensive to produce.
Setting aside AMD's stupid marketing, the AMD FX-8150 is a very efficient QUAD core.
The performance per core is almost as good as Sandy Bridge, in properly threaded applications.
Then they came with the marketing stunt of calling it a 8 core.. it's not, in fact it doesn't have 8 COMPLETE cores; in terms of processing units, an 8 core Bulldozer is very close to a Sandy Bridge QUAD core.
The only reason why Bulldozer's die is so large is the enormous amount of cache, which i'm sure makes sense only in the server environment, while the low latency / high bandwidth cache of Sandy Bridge is much more efficient for common applications.
I think with Bulldozer AMD has put a good foundation for the future: today, on the desktop, there is no reason not to buy a Sandy Bridge (however i'm expecting Bulldozer's street price to drop pretty quickly).
However IF AMD is able to execute the next releases at the planned pace (+10-15% IPC in 2012 and going forward every year) THEN they'll be back in the game.