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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GatorLord - Thursday, October 13, 2011 - link
OMG! That is some seriously funny sh1t! I thought I'd blow a kidney or something...I'm trying to type this though the tears I was laughing so hard!I800C0LLECT - Thursday, October 13, 2011 - link
I think majority of these comments show just how fickle consumerism is in America. Anyways, tomorrow's vision vs. current real world performance is the rats nest.They obviously pushed this towards server markets. Maybe that's why there wasn't much fanfare with the marketing gurus?
The performance obviously doesn't reach out to the niche market of computer gamers. Let's see how lucrative this becomes if AMD is able to crack the not so trendy server market. Those guys don't like to break old habits. Stability is kind of a big deal.
I can also see how this design creates a plug and play product for many different markets. The downside to that is it's one design for all which has already proven inefficient for Gamers. But what about consumer electronics? They generally want cheap and simple. Performance be damned.
Interesting hand AMD.
CharlieBBarkin - Thursday, October 13, 2011 - link
I'd hate to break it to you, but even though Bulldozer was targeted towards the server market, it is a complete non-starter in that segment. Look at the power consumption of the Bulldozer. It's off the charts, and it has less raw performance than Intel chips. I can't imagine any system administrator dumb enough to install Bulldozer chips into any sort of compute or server farm. Why would a farm waste money powering and cooling Bulldozer chips when it would be so much cheaper and higher performance to just use Intel CPUs?silverblue - Friday, October 14, 2011 - link
Could just be the ASUS board causing the issues. At any rate, once you overclock past a certain point, power usage just accelerates madly, and you're not going to see these sorts of high frequencies on the server anyway so the point is rather moot. Additionally, with servers, they're a little more focused on power efficiency than with client machines. Magny Cours was a 12-core CPU and the 6176 had a TDP of 105W if I'm correct, so despite its 2.3GHz clock speed, that's not too bad considering.luckylinux - Thursday, October 13, 2011 - link
I also have waited for a long time to finally see if I could replace my phenom ii x4 and x6 with the new super bulldozer. Nevertheless I'm pretty disappointed by the raw performance of this new chip.I began using amd products about one year and a half ago, so I'm not really an amd fanboy ... however began to like them for their choice of not doing the intel shitty hobby of switching 3 sockets every 2 years.
Took an athlon x2, x4, phenom ii x6 and two E-350 from them and very happy for what you get (a bang for your money).
However ... looking at the athlons (and even more the phenoms) power consumption is rather disappointing compared to sandy bridge cpus which I recently bought (yeah, I did not want to leave a 24/7 machine on drawing 60 Watts at idle when SB idles at much less with their power gates tech).
Bulldozer power gates are rather disappointing. Hoped for much higher frequency or lower power consumption at load due to the transistor shrink. And 2B transistors ????? Seeing as some compenents are shared across cores I think this is WAY too much !
BUT one thing deserves to be said. In my case (but that's just me, eh) I wanted a multicore processor which supported both AES-NI and ECC memory. For ECC you can either take an ASUS AM3(+) motherboard (about 120$ the cheapests of am3+), either a 1366 or a 1155 C202/4/6, which costs about 260$ at least ! For AES-NI the only alternative seemed up til now to go with Xeon which cost quite a bit more. Furthermore Xeon cpus are not so easily to get your hands on.
I think that no one gave credit for their efforts to implement AES-NI. If you want a home server that's a very appreciated bonus.
Although I can understand why many of the users here are angry at the new chip because it doesn't perform very well in gaming, the choice of amd to disregard single threaded apps in itself is quite good. In a market where in a few years we'll see 40+ cores on a single desktop CPU (well, in server that'll be next year with Komodo !) what the heck can you obtain with a single core ? Idling 39 cores to speed up one core to 8GHz (assuming that's electrically possible). Silicon dictates the limits on the frequency you can use in your chip. AMD understood this long ago, when intel and their S775 tried to surpass the 3GHz wall with the Pentium IV. Since we're going in a multithread world, 40 x 4GHz (something like that at 22 or 10nm I think) will perform WAY better that 1 x 8GHz (provided that apps are well developed). Why INTEL does not understand this (S2011 provides only 6 cores !) ? However with 2B transistors a few more cores could've been added :D AMD has to work better at power consumption. Instead of clock per clock performance they focus on # of cores which is what the future is ! You will say that intel's performance per core is almost the double, but amd cores are twice so ... How long will intel continue to release quads when amd'll get to sixteen ? If you're an intel fanboy just say that amd BD is shit, but I think this kind of strategy is going to pay in the long term. In fact amd manages to put more cores in a single die, whereas intel is always 2 cores behind. That alone shows that AMD engineers aren't idiots !
luckylinux - Thursday, October 13, 2011 - link
EDIT: Komodo will have 20cores (only :D)I800C0LLECT - Thursday, October 13, 2011 - link
More cores?I guess I was trying to infer that as fabrication processes we shrink to 22nm, etc. How much over head is reduced by plugging in a few more cores vs. new design and architecture?
I'm wondering if AMD just set the foundation for something big?
Seems like they bet on software making some leaps and bounds.
wolfman3k5 - Thursday, October 13, 2011 - link
It's finally here! I have been waiting for one of these. It's another Hitler Video, this time it's about Bulldozer. Funny as hell...The video can be found here: http://www.youtube.com/watch?v=SArxcnpXStE
just4U - Thursday, October 13, 2011 - link
Ok, in several reviews now I've heard about the lacklustre single threaded performance.. Just how bad is it? If you had to compare it to another cpu out there which intel and which amd cput would it compare to?Desperad@ - Thursday, October 13, 2011 - link
Promises of AMDhttp://blogs.amd.com/work/2010/08/23/%E2%80%9Dbull...
http://blogs.amd.com/work/2010/08/30/bulldozer-20-...
http://blogs.amd.com/work/2010/09/13/bulldozer-20-...
http://sites.amd.com/us/promo/processors/Pages/ope...