Technology for Mortals

AMD had much to celebration last week as they managed to beat Intel’s Nehalem-EP to the mainstream two-socket server market with Shanghai.  AMD took a lead in SPECjbb, SPECweb, SPECfp, and Virtualization Nested Paging for the server market and it looked like they might have had 2 months of breathing room to before Nehalem-EP arrives in the two-socket server market.  But there was an unexpected party crasher today when a single Intel’s Nehalem i7-965 3.2 GHz single-socket processor for the desktop market decided to take on two brand new AMD Shanghai processors in the server benchmarks and win.

In the server space, the most commonly cited benchmark is general purpose integer performance which is measured by SPECint.  The table below shows the latest results from SPEC.

AMD and Intel have been neck and neck in the server market in the last 4 years but never has a single top-end CPU from one competitor between two top-end processors from the other competitor.  Even on SPECfp high performance computing where AMD has dominated for the alst 4 years, the single i7-965 Nehalem comes relatively close to the performance of two Shanghai processors which almost guarantees dominance for Nehalem-EP two-socket servers when they arrive in a few months.

The Intel Nehalem i7-965 is showing a hint of what’s to come when Nehalem-EP arrives in two-socket configuration.  In the past, Intel had difficulty scaling sockets because they remained on a single North Bridge memory controller and the Front Side Bus (FSB) but those days are gone with Nehalems integrated memory controller and new QuickPath interconnect architecture.  As a result, the performance of Nehalem-EP is expected to scale extremely well because the number of memory controllers (built in to the Nehalem die) and the number of DDR3 memory channels will double.  This means we may see a two socket Nehalem-EP server crack 200 points on SPECint_rate_base2006 which is a massive leap for the mainstream server market.

Update 11/23/2008 – TechRadar has a first look at Nehalem-EP dual-socket and the performance is off the charts.

One issue that I’m frequently asked about is AMD’s alternative energy efficiency rating called Average CPU Power (ACP).  AMD created this new standard on its own last year and despite controversy, they’ve managed to get the media to accept this new definition of energy efficiency.  AMD has told the press that AMD’s ACP rating is equivalent to Intel’s TDP rating and I know this because this is what AMD spokesperson John Taylor told me when I was Editor at Large at ZDNet.  Here’s an excerpt of what he emailed me on September 10th 2007:

“We believe that for the datacenter customer, AMD ACP is a more useful metric when configuring/budgeting. As Intel TDP is the only available metric for Intel, it is the most comparable to AMD ACP. The trick is: how does intel formulate its TDP? My sense is it is defined very closely to AMD ACP, which reinforces a “yes” answer to your question. But i’ d’ prefer Intel confirm that.”

Well I’ve not only spoke to Intel which emphatically denies this, I know for a fact that this comparison is not correct and I’ve also gotten David Kanter (one of the leading microprocessor analysts in the world) to corroborate this.  I asked David Kanter to review AMD’s claim that Intel’s TDP rating was “most comparable” to AMD ACP and he explained:

“It’s pretty hard to justify the comparison between the two from a technical perspective.  AMD’s ACP is defined in a very different way from Intel’s TDP, according to my understanding.”

We can easily verify that AMD’s ACP rating is not comparable to Intel’s TDP rating by looking at the actual performance of the newest AMD Shanghai based servers versus Intel’s current servers.  When we look at the official published SPECpower measurements between an AMD “Shanghai” 2384 2.7 GHz system with an ACP rating of 75 watts and an Intel L5430 with a TDP rating of 50 watts with comparable components in the rest of the server, we would expect a power difference of roughly 50 watts (25W per processor) if AMD’s claim that AMD’s ACP was most comparable to Intel’s TDP rating.  But according the official SPECpower benchmarks which is optimized for low power consumption, the Intel L5430 server peaks at 161 watts while the AMD 2384 based server peaks at 264 watts.

That’s more than a 100 watt delta and when we account for the fact that the Intel server has an additional North Bridge memory controller to deal with, the actual difference between the CPUs is even greater than 100 watts.  We can negate the fact that the AMD server has two more memory DIMMs which consume an additional 8.4 watts of power because AMD uses hard drives that use 6 watts less power than the Intel system.  This strongly suggests that an AMD TDP rating of 95 watts is far more likely to explain the 100 watt more power consumption than the Intel system with 50 watt TDP processors, so calling the “Shanghai” 2384 processor a 75 watt part simply doesn’t reflect the actual efficiency of the chip.

Based on what the experts say and what the evidence suggests, AMD claiming that their ACP rating is comparable to Intel’s TDP rating is simply incorrect and the ACP rating is effectively overstating the energy efficiency AMD processors.  This is the equivalent of a car company that came up with its own Miles Per Gallon (MPG) fuel efficiency rating to inflate its actual MPG rating.

Now to be clear, TDP was never meant to be an energy efficiency rating but it is in effect exactly that when it’s used in the context of advertising and press releases.  TDP is actually an engineering metric for server manufactures to figure out what kind of cooling they have to design in to their system to accommodate a CPU.  A far more appropriate measure that people should be looking at for servers is the SPECpower rating.  But if the media insists on quoting CPU wattage ratings, they should use a consistent measurement and the only one that is comparable and accepted by the entire industry is TDP.

AMD launched its 45nm Shanghai processors today for the server market ahead of Intel’s Nehalem processor launch.  AMD lists a series of benchmarks here but they omit many of the better results from Intel.  To get the full official results, here are the benchmarks based on the best scores available from AMD and Intel as of November 13th 2008.

It appears that AMD has made some important gains and it has taken the lead in SPECjbb, SPECweb, expanded its lead in SPECfp, and Virtualization (due to Nested Paging).  AMD still trails in SPECint, SPECpower, and SAP but this is an important victory for AMD which has been plagued with delays in 2007 and 2008 with its previous Barcelona processor.  Shanghai is a major milestone for AMD because it required a shift to a whole new 45nm immersion lithography process and it shows that AMD can launch a product on time and put Barcelona behind them.

However, Intel is expected to launch its Nehalem-EP processors for the mainstream two-socket server market within a few months and Nehalem is expected to be a huge jump in performance on the server platform.  While the new triple-channel DDR3 unbuffered memory subsystem doesn’t do too much for the Intel i7 Nehalem desktop processors, it is expected to unleash a huge increase in performance for Intel Nehalem.

Intel’s Penryn class of processors launched last year will be the last generation of Intel processors to use the Front Side Bus (FSB) and a single North Bridge memory controller located on the motherboard.  The FSB and single North Bridge memory controller wasn’t a problem for most of Intel’s product line but it significantly hampered Penryn’s performance in the two-socket market at higher clock speeds.  But this wasn’t a problem since AMD had trouble launching its Barcelona products early enough and at high enough clock speeds to threaten Penryn on the high end, and only now are the newest AMD Shanghai processors competing head to head with Intel Penryn.  Some people wondered why Intel stuck with the FSB architecture for so long, but the timing seems to have been appropriate given the outcome in the last two years.

Intel’s Nehalem will be too fast to run on FSB architecture which is why Intel designed it with QuickPath.  Nehalem will have no such memory bandwidth limitations as it transitions to QuickPath architecture with a memory controller on each microprocessor.  Nehalem also catches up with AMD on nested paging support for improved virtualization, but the late timing doesn’t seem to have hurt Intel given the fact that virtualization hypervisors are only now beginning to support nested paging.  So the race is on to see how quickly AMD can ramp up Shanghai processors and how long it takes Intel to launch Nehalem.

I just came across some certified SAP server benchmarks for the soon to be launched AMD 45nm Shanghai processor in comparison to some Intel Tigerton 65nm processor and Intel Dunnington 45nm processor.

While I’m not 100% certain that the Opteron 8384 is a Shanghai processor, the fact that it has 128 KB L1 cache and 512 KB L2 cache per core, and 6 MB L3 cache per processor is a pretty good indicator that it is Shanghai.

The Intel Dunnington server probably holds the edge because of its single die monolithic 6-core CPU whereas the Shanghai only has 4-cores.

Also, more Shanghai results here.

Performance benchmarks are the equivalent of the Indianapolis 500 for the computer industry, if not more important.  Rarely are the top performance numbers attainable in the real world, but winning is a critical symbolic victory in the war of perception.  The winner of the benchmarks will be perceived to have a technological lead across their entire line of products while the loser is perceived to be inferior across their entire line of products.

Benchmarks are like races and the winner is always determined by the best performance.  The only fair way to conduct benchmarks is to have each player put forth their best player to achieve the highest scores possible within a common set of rules and parameters.  By this measure, AMD’s recent submission of SPECpower energy efficiency benchmarks on behalf of Intel servers which portray Intel in a sub-optimal light while ignoring superior scores for Intel is highly inappropriate.

AMD says that their system gets a score of 731 while the Intel system that AMD submitted gets a score of 561.  AMD claims this is a legitimate comparison because the systems share many commonalities and they defend their behavior by saying:

“if we were trying to show worst case scenario we would have turned off Power Management on the Intel server”

But the fact that AMD could have turned in even worse performance numbers for the Intel system is totally irrelevant.  If anything, submitting plausible performance numbers on the Intel system is far more insidious because it is a more effective deceit.

The obvious problem with AMD’s explanation is that the Intel system submitted by AMD shows a poorly optimized hardware configuration for Intel in terms of energy efficiency.  The system uses Fully Buffered memory DIMMs which are notoriously inefficient for the Intel system when the most efficient Intel systems use unbuffered DIMMs.  Intel launched the San Clemente 5100 series chipset exactly one year ago which uses the same unbuffered memory as AMD.  While it’s true that Intel initially went with Fully Buffered memory two years ago, it was obviously a mistake given the power consumption and Intel quickly fixed that mistake last year.  With Nehalem-EP two-socket servers coming at the end of this year, Intel will only use ECC unregistered or registered DIMMs and they will completely shun FBDIMMs.  The bottom line is that anyone looking to build an efficient Intel-based server today should use unbuffered memory and AMD conveniently forgot to do that.

The other possible problem in AMD’s explanation is that they used the “same JVM command line options” for the Server Side Java (SSJ) benchmark.  While this sounds like a fair comparison, it’s common for different CPUs from different vendors to require different command line options to achieve optimum results.  This may explain why the AMD-submitted Intel server was 5% slower than comparable Intel systems submitted by other vendors.  Combined with the suboptimal Intel hardware and possibly suboptimal software configuration, we can see the likely reason why the AMD-submitted Intel system did so poorly.

To get an accurate picture of what’s really going on, we need to look at the best possible SPECpower scores for AMD and Intel to determine who the actual winner is.  The table below compares the official SPECpower_ssj2008 energy efficiency benchmarks of the top dual-processor servers from Intel and AMD.

Because the SPECpower rules don’t really specify the minimal number of memory DIMMs that a server should have, AMD should have submitted servers with 2 DIMMs like everyone else to get the best scores.  Instead, AMD submitted servers with 4 memory DIMMs instead of 2 which gives them a 3.58 idle watts to 8.42 peaks watt handicap.  However, AMD neutralized that handicap using the newest Western Digital GreenPower 3.5″ hard drive which saves 4 idle watts to 6 active watts compared to the hard drives used by the other systems.

But for the sake of comparison, I estimated the scores of the 3 Intel systems that used only 2 DIMMs and added 3.58 watts in idle and gradually increased up to 8.42 watts at peak Server Side Java (SSJ) loads to simulate power consumption for a 4-DIMM server.  But when these servers get upgraded to 4 DIMMs, they have higher memory performance which translates to higher overall performance.  Based on the peak SSJ scores in the table above, I estimated a 2.5% boost in peak SSJ performance which slightly counteracts the negative effects of the higher power consumption in terms of performance per unit energy.  Based on this estimate (which should NOT be taken as official SPECpower_ssj2008 scores), I calculated that the top three systems in the table above would have achieved a score of 1006, 889, and 836 which is still higher than the AMD servers.  But if those top three Intel servers had used the same energy efficient hard drives used in the AMD servers, the score reverts back to something similar to the unadjusted numbers.

UPDATE 11/13/2008 – The AMD results were actually not Barcelona, but AMD Shanghai results.  I had thought they were Barcelona but I didn’t realize that I was looking at yet-to-be-launched Shanghai performance numbers.

In conclusion, AMD has made huge strides to nearly close the SPECpower gap, but they’re behaving inappropriately by comparing their products to suboptimal benchmarks that they themselves submitted.  That’s unfortunate because this new controversy has overshadowed the huge progress made by AMD.  Had AMD launched these mid 2 GHz Barcelona processors on time a year earlier, they would have been extremely competitive all through 2008 but it was not to be and they suffered for it.

AMD made some huge clock-for-clock core-for-core performance gains with their quad-core Barcelona chips in Server Side Java (SSJ) performance compared to their older dual-core Opteron chips.  Even when I factor out the clock speed difference, a Barcelona quad-core 2.7 is still 3.14 times faster than an Opteron dual-core 2.4 GHz system in Server Side Java performance.  These gains have allowed AMD to become very competitive against Intel’s aging Penryn chips although AMD cannot claim the title.  It’s also interesting to note that AMD Barcelona also made huge improvements in web server performance and it is beating Intel Penryn servers on dual-socket SPECweb_2005.  However, Intel Penryn class CPUs still win by a large margin in the single-processor server market.

The reason for this disparity between single- and dual-socket servers is that Intel’s memory architecture is constraining their dual-socket performance, but that limitation will soon disappear with Intel’s Nehalem Microarchitecture server CPUs which should launch by the end of this year.  Intel’s Nehalem CPUs have completely closed the memory performance gap with QuickPath architecture and they’ve even managed to leapfrog AMD’s memory architecture with 50% more memory channels and higher performance DDR3 memory.  Coupled with the improvements in the Nehalem execution engine, there is little doubt that Intel will be regaining a comfortable lead in the Server and Desktop markets.

AMD will narrow that gap with their Shanghai processors if they can launch on time but few analysts predict Shanghai will come close to beating Nehalem.  Whether or not AMD can launch Shanghai on time or get close enough to Intel Nehalem to be reasonably competitive remains to be seen.

I (finally) wrapped up a 6 or 7 month long struggle with my video card. See, some time ago, some update or another did something… odd… with my video card (an NVidia 7600 GS, for the record, the best passively cooled, dual DVI output card I could find when I put this PC together). It started doing this “thing” where major portions of the screen would be transparent to the layer beneath. Oddly enough, it only occured when a game was running full screen. Let me tell you, it was quite odd going through Half Life 2 (I know, I am WAY behind the times) being able to see through walls if I get right next to them. In many situations, there would be some odd “snow” in areas too. To make it even more strange, the games would work fine the first time they were run after a reboot, or if I started the game in a window and then told it to run full screen. Needless to say, it really sucked.

For the last umpteen months, I would occassionally fool with it for a few hours… messing with settings, updating drivers, searching the Internet. A friend of mind reported that he had an identical problem. I was loathe to revert to a much older driver, because I had severe performance problems with some of them. I kept meaning to purchase another video card, but frankly, I find purchasing desktop-grade hardware that is paid for from my bank account to be quite stressful. I’ll price out $10k worth of server kit in a few hours, including vendors and SKUs, but for some reason, personal PC equipment turns me into a neurotic diva. Of course, for the money I could have earned in that time I spent wrangling with the existing card and picking out a new card, I could have bought a whole new PC…

I finally picked out a suitable replacement, a low end Sapphire Radeon card (no way was I going back to NVidia). Ironically, I purchased the NVidia card because ATI cards have had so many driver problems over the last few years. For my needs, which are quite low end (a few older games, driving a pair of monitors for typical business usage), I don’t need anything fancy. I need it to not cause me headaches.

I finally solved my problem this weekend, by dicovering that NVidia driver installers leave themselves on my drive, and I found a driver from before the problem. After installing it, it worked like a charm.

But I find the whole situation rediculous. ATI and NVidia have both had very long (as in, “a few years”) periods where they had a bad driver reputation. Imagine if, say, drive controllers were as unreliable as video drivers. You know, doing things like resetting the driver and “going blank” for five minutes at a time (my previous ATI card did this, to solve the problem I’d use the keyboard to get the PC to sleep, then wake it back up) with no warning. I am sure that people would love their hard drives doing that. Or if waving the mouse around too fast caused the system to blue screen, blaming a failure in the mouse driver. Yeah, that’s going to move a lot of units. I can see the computing public loving to have to search out drivers for their sound card because their current card does not play Outlook’s new mail notification sound properly, due to a driver incompatbility with Outlook (but not Word or Excel).

Now, I know that there is a certain reality here. Video drivers are very complex. They involve a lot of fancy algorithms, optimizations, and so on. They need to be compatable with a ton of applications and APIs which are doing some tricky things. The hardware operates under some very tight constraints. But you know what? So does an F-15. If F-15’s had drivers written by ATI or NVidia, the US Air Force could be pwn3d by the local RC airplane club. Seriously.

NVidia, ATI… get with the program. This situation is only possible because you two have a duopoly. Someone’s going to eat your lunch someday, and bad drivers are the worst form of customer service possible. I’d jump for the chance to give a 3rd party my video card dollar (as little as I spend on them) provided that the drivers weren’t junk.

J.Ja

AMD just released a “new” low-power 1.8 GHz quad-core model X4 9100e and dubbed it “the world’s first 65W desktop processor”.  But this claim seem to be dubious when you consider what AMD had to do to get to that power level and what they’re up against.

• AMD uses very low clock speeds to achieve these power numbers.  The 9100e is clocked exceptionally low for a modern day processor which gives it horrible single- or dual-thread performance compared to a less expensive dual-core 2.5 GHz or 2.66 GHz Intel processor.  For the desktop market, it’s hard to see where a low-clocked quad-core makes sense.
• The other problem is that this is a very qualified and questionable victory in actual power performance.  Anytime you drop the clock speed in a given processor, the power consumption will drop.  Intel for example offers their 50W 2.5 GHz 45nm Penryn-class chip called “Harpertown” in the lucrative server space but chooses not to offer this chip in the desktop space.
• Even Intel’s 2.66 GHz 45nm quad-core “Yorkfield” model Q9450 would come very close to the AMD 1.8 GHz 9100e quad-core in power consumption.  This is fairly certain since TechReport, LostCircuits, and HotHardware all showed how close the QX9650 3.0 GHz 45nm came to 65W TDP dual-core CPU performance which is nothing short of amazing.  The only anomaly is this recent set of power benchmarks released by TomsHardware which strangely claims that a 45nm Q9450 2.66 consumes more power than an Intel Q6600 2.4 GHz 65nm processor which goes against every 45nm power benchmark I’ve ever seen.  As soon as the AMD 9100e quad-core becomes available, I’ll try test it against an Intel 45nm quad-core to verify.
• But the biggest problem with this 9100e is that it is based on the buggy B2 stepping which has that infamous TLB (Translation Lookaside Buffer) bug that cripples performance when it’s patched.  It would seem as if AMD is taking their leftover stockpiles of B2 stepping chips and repackaging them as energy efficient CPUs.  So we’re talking about a low-clocked low-performance chip to begin with that has to take an additional TLB patch performance hit.

So why did AMD go with a buggy chip?  It would seem that getting rid of excess buggy B2 stepping CPUs isn’t the only motivation.  I got this set of stunning data below from someone I know who we’ll call “Jack” for the time being.   Jack has a PhD in Physics and he is also a huge CPU technology enthusiast.  Jack sent me the following power reading chart comparing two AMD X4 quad-core CPUs at identical voltage and clock speeds.  The AMD 9850BE is a B3 stepping CPU and the AMD 9600BE is a B2 stepping CPU.

The reason the 9850BE voltage and clock was dropped down to the level of the 9600BE was to provide an apples-to-apples comparison between the B2 and B3 process.  As you can see, there is still a 16 to 20 watt delta between idle and peak power consumption between these two chips.  What this seems to suggest is that the B3 stepping consumes more power than the B2 process as a tradeoff for higher clock speeds.  In fact, this may explain why AMD silently increased their TDP ratings in their quad-core Opteron CPUs which use the same die as the X4 desktop quad-core processors.

This explains why AMD would use the B2 stepping despite its TLB bug to produce their first 65W TDP desktop quad-core desktop processor where the market isn’t as discriminating as the server market against processor bugs.  But why does AMD’s B3 stepping consume more power than the B2 stepping?  Jack’s theory is that the gates are thicker in B2 which avoids leakage.  His theory is based on the following observation:

Jack: In Nov. Semi International reverse engineered a Barcelona and quoted a gate thickness it was 15% HIGHER than what AMD disclosed at the IEDM in 2005.”