Cache and Memory Performance

I mentioned earlier that cache latencies are higher in order to accommodate the larger caches (8MB L2 + 8MB L3) as well as the high frequency design. We turned to our old friend cachemem to measure these latencies in clocks:

Cache/Memory Latency Comparison
  L1 L2 L3 Main Memory
AMD FX-8150 (3.6GHz) 4 21 65 195
AMD Phenom II X4 975 BE (3.6GHz) 3 15 59 182
AMD Phenom II X6 1100T (3.3GHz) 3 14 55 157
Intel Core i5 2500K (3.3GHz) 4 11 25 148

Cache latencies are up significantly across the board, which is to be expected given the increase in pipeline depth as well as cache size. But is Bulldozer able to overcome the increase through higher clocks? To find out we have to convert latency in clocks to latency in nanoseconds:

Memory Latency

We disable turbo in order to get predictable clock speeds, which lets us accurately calculate memory latency in ns. The FX-8150 at 3.6GHz has a longer trip down memory lane than its predecessor, also at 3.6GHz. The higher latency caches play a role in this as they are necessary to help drive AMD's frequency up. What happens if we turn turbo on and peg the FX-8150 at 3.9GHz? Memory latency goes down. Bulldozer still isn't able to get to main memory as quickly as Sandy Bridge, but thanks to Turbo Core it's able to do so better than the outgoing Phenom II.

L3 Cache Latency

L3 access latency is effectively a wash compared to the Phenom II thanks to the higher clock speeds enabled by Turbo Core. Latencies haven't really improved though, and Bulldozer has a long way to go before it reaches Sandy Bridge access latencies.

The Impact of Bulldozer's Pipeline Windows 7 Application Performance
Comments Locked

430 Comments

View All Comments

  • Pipperox - Saturday, October 15, 2011 - link

    With a 40-50% gain Bulldozer would be even ahead of Ivy Bridge.. and what comes next.

    Or are we still talking about SuperPI?
    Or games run at 640x480 lowest quality settings?

    The fact is, almost all single threaded applications are old and they run already super fast on ANY cpu and the difference can be seen only in benchmarks.

    All recent performance demanding applications are properly multithreaded, and Bulldozer there is competitive with i5 2500 and occasionally with i7 2600 (and with a 10% boost Bulldozer would be competitive with i7 2600).

    And this will become more and more the standard one year from now.

    Sure Bulldozer has not met the enthusiasts' expectations, it doesn't perform as people would expect an "octacore" (but it's not, it's just a quad with a different form of hyperthreading and "clever" marketing) and it doesn't deserve the FX moniker.

    But still it's the most competitive CPU AMD has launched in years, perhaps with the exception of Zacate.
  • nirmv - Saturday, October 15, 2011 - link

    Not all applications are heaviliy multi-threaded, there is still need to improve single thread performance.
    And even for those few loads that are competitive in performance, they do it with twice the power draw.

    See here from xbitlabs review :
    http://www.xbitlabs.com/images/cpu/amd-fx-8150/pow...
  • Pipperox - Sunday, October 16, 2011 - link

    But increasing single threaded performance has a cost, on die space and circuit complexity.
    Bulldozer has a huge die just because it has enormous caches (8MB L2 vs 1Mb on SandyBridge) which probably will turn useful on server workloads (but that's just a guess).
    By looking at the die shot, you'd get a 40% die area reduction with "normal" caches.
    So AMD engineers decided to drop single threaded performance improvements in favor of higher multithreaded scalability and higher clock speed scalability.

    We'll see if in the long run this will pay off.

    I agree power consumption doesn't look good in comparison with Intel, but it does look good in comparison to Thuban.

    This is the first released silicon of Bulldozer.. i expect power consumption to improve with newer steppings and silicon process tuning.

    That being said, Intel has the best silicon process in the whole industry.
    AMD can't compete with that.
    But i'd guess that at lower clock speeds (like in server), AMD's power consumption will improve a lot.
    Looks like with the FX AMD tried to push their current silicon to the maximum which they could (within the 125W TDP which is sort of an industry standard).
  • LiveandEnjoyLife - Friday, October 14, 2011 - link

    Some people are missing the point. At this stage in the game, processor speed is a moot point beyond benchmarks. AMD and Intel make very fast CPUs in relation to what gamers and every day users use them for. Intel CPUs are blazing fast and AMD CPUs are fast. The average Joe does need more than a dual-core CPU. If you were going to actually do something that would require heavy multi-threading, then it comes down to the efficiency the app to make use of the cores and the ability to use hyperthreading. If you wanted the most performance for a mult-threaded application, you would pick more physical cores over virtual cores. So for most of use it comes down to bang for buck.

    8 cores is better than 2, 4, or 6 for true multi-threaded capable applications.
    For speed tests Intel wins hands down.

    If you were sitting next to someone playing a game and all things were the same except CPU, you would not be able to tell which machine is running what CPU. However you would notice if one costs significantly more than the other.

    That is my 4 cents.
  • 7Enigma - Friday, October 14, 2011 - link

    Hi Anand,

    Great review but there is a text error when referring to pass one vs. pass two of the benchmark mentioned in the Subject line. You said:

    "The standings don't change too much in the second pass, the frame rates are simply higher across the board. The FX-8150 is an x86 transcoding beast though, roughly equalling Intel's Core i7 2600K. Although not depicted here, the performance using the AMD XOP codepath was virtually identical to the AVX results."

    But the graph clearly shows a complete flip-flop from first pass to second pass. When I look closely it appears you ordered the text and graphs differently and were referring to if you had the non-AVX and AVX-enabled graphs next to each other instead of in separate sections. Basically the text and graphs don't match up.

    HTH
  • Iketh - Friday, October 14, 2011 - link

    You're an utter retard. The reason they're sold out is newegg advertised these nicely all over their site, including the front page, with "World's first 8-core desktop processor."

    There are plenty of reasons to purchase these processors aside from their performance and that's ok. But the majority bought them thinking they're gonna "rock", and those are the ones "showing intelligence." Same goes to you for thinking the majority is well-informed/intelligent.

    What's even worse, the 8-core version for sale is the 3.1ghz, not the 3.6 tested in this review. I'm seriously LOL'ing...

    How many did Newegg have in stock anyhow? Wouldn't that figure matter regarding your ignorant comment?
  • rcrossw - Friday, October 14, 2011 - link

    I have used AMD products for years. I use Intel at work. So to me there is no real difference between the two for what Business and the Average Computer user want or expect.
    Does it run, does it do the work I require of it, and do my programs and Network Access
    work well and are reliable?

    Intel indeed has incredible Processors, fast and reliable, and in the high end - expensive.

    AMD is Low and Mid range - with processors that the average person can afford. Who is the most innovative - both. Today Intel has been , now I think the user needs to give this New X86-64 Architecture a chance.

    I have a Asus M5A99x EVO with an FX6100 installed. The only problem I have had is having to upgrade the BIOS to accept the new Processor. So far I have had the Processor to 4.2 Ghz. Though AIDA 64 caused a BOD on one test. At 3.8 Ghz runs like a champ. Stil
    working back to as close as I can get to 4.2 on Air.

    After three years I have retired my old Phenon II Tri Core 720 for this, and it works for me.
    I am not an extreme gamer, etc. But test it your self, before being too overly critical.

    Does it work for me.

    As an aside, next a SSD for faster response.

    For those interested:

    Asus M5A99x MB BIOS 0810 ( Newest)
    AMD FX 6100 at 3.8 ghz
    Corsair Vengeance 1600 - 16 gigs
    HIS Radeon HD 6850
    Windows 7 Ulimate 64
    HPLP2475W Monitor at 1920x1200 DP
    WD 500 SATA
    WD 1001 SATA
    LG H20L BD-R
    Plextor DVDR
    Enermax 620 Liberty PS - I know old but works.

    Thanks
  • davbran - Saturday, October 15, 2011 - link

    I have been having a hard time writing a comment on this topic without drawing fire from trolls.

    This review is hogwash without more information.

    If the hardware is the same on all test machines, apart from the CPUs, then there is no wonder the performance was so bad. 6 Cores are going to utilize, and I am just pulling a number out of my ... hat, 4gb of RAM more efficiently than an 8 core using simple kitchen math. No need to break out the slide rules. It's a known fact, to most, that the big bottleneck in the multicore/multiprocessor world is memory. Mind you that's if we are factoring in that all the code that was used for testing purposes was written with multi-threading in mind.

    You just can't compare apples to bananas in this manner.
  • silverblue - Saturday, October 15, 2011 - link

    Each to their own. I thought it was a pretty good review, and Anand certainly held back from slating AMD to hell.
  • Iketh - Sunday, October 16, 2011 - link

    LOLLLLL

Log in

Don't have an account? Sign up now