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Is Intel’s X79 Really Worth it?

by Mark W. Hibben

The Chipset Formerly Known as Sandy Bridge E Gets a Luke Warm Reception

With little fanfare, Intel finally rolled out the successor to the X58 chipset and LGA 1366 family, dubbed the X79, mated with a new series of LGA 2011 processors.  Intended to be Intel’s highest performance desktop platform, X79 clearly targets high performance PC enthusiasts and gamers.  Initial reviews and test results demonstrated that, yes, the new Core i7-3960X Extreme Edition processor is faster than the latest Sandy Bridge (SB) “2nd Generation” Core i7 processors.  With 6 cores, 4 independent memory channels, and 40 PCI Express lanes, it had better be.  But the steep price and the lack of internal video processing had some reviewers wondering whether the upgrade from Sandy Bridge was really worth it.  Even more distressing for gamers, many test results showed little 2-way SLI or Crossfire performance improvement compared to Sandy Bridge, even though Sandy Bridge processors are limited to 16 PCIe lanes vs. 40 for Sandy Bridge E (SBE) processors.

Tough Act to Follow

Part of the problem with X79 may simply be that it arrives in the wake of Sandy Bridge, which in many ways has become a landmark for desktop and mobile computing.  As I described in my Sandy Bridge preview late last year, Sandy Bridge initiated an evolutionary process inspired by low-power Systems-on-Chip (SOCs) in which many external functions were consolidated onto the main processor.  As I show in the diagram on the next panel, Sandy Bridge (shown in the latest Z68 chipset incarnation) moved the high bandwidth PCI Express interface from the IO Hub of X58 onto the processor itself.  This allowed the IO Hub to be eliminated so that the external “chipset” was reduced to a single Platform Controller Hub (PCH). 

With relatively low bandwidth data moving to the PCH, the high performance Quick Path Interconnect (QPI) could be eliminated in favor of an updated Direct Media Interface (DMI) running at 2 GB/s raw data rate in each direction, sufficient for peripherals such as SATA 3.0 drives, USB 2.0 ports, and Ethernet controllers.  With Sandy Bridge, all the really high bandwidth interfaces, memory and video card, went directly to the processor, thereby eliminating the IO Hub as a data bottleneck. 

There was a price to be paid for the higher on-chip integration in the form of fewer memory controller channels (2 vs. the 3 of X58) and fewer PCIe lanes.  The additional PCIe lanes provided by the PCH weren’t always available on a given motherboard, since the extra lanes were often used to interface to Ethernet controllers or additional SATA 3.0 controllers.  But there was so much goodness baked into Sandy Bridge that most users probably didn’t notice the design compromises. 

The processor/chipset combination had been designed from the ground up for lower power consumption, with very low power draw for CPU idle states.  Most importantly, the internal graphics processor (Intel HD 3000) provided a much lower power display driver than most external graphics cards, even ones intended for mobile applications.  Since most Sandy Bridge systems provided a way to dynamically switch between internal and external graphics, even performance users could happily switch in their high performance (and very power hungry) graphics cards when needed.  Sandy Bridge, with its combination of power management and multi-core performance, provided a highly capable platform with a much reduced carbon footprint compared to previous generations of Intel chipsets.

The Next Level of Performance

As good as Sandy Bridge was, there was clearly a need to take performance computing to the next level.  I love my Sandy Bridge MacBook Pro, and I use it for about 60% of what I do every day.  Web page construction, image editing, article writing, code development, these it can handle no problem, but it starts wheezing (in the form of noise from its dual cooling fans) on the compute intensive tasks like video editing.  And when I want to use a second monitor (easily plugged in through the Thunderbolt port), the external graphics are automatically switched in, and much of the power efficiency of the system is lost.  Just the need to use multiple monitors renders the internal graphics capability superfluous.  Thus I’ve had to face the fact that for that remaining 40% of my work load, Sandy Bridge (in its mobile version) isn’t a good fit, but Sandy Bridge E, as implemented in the X79 chipset is.  X79 makes a great personal workstation, able to address massive memory and disk storage, utilize 6 physical cores (12 virtual cores), and support multiple graphics cards if you need them for CUDA processing or more than two monitors.  Also, the extra PCIe expansion provides more flexibility for adding even higher performance RAID controllers such as Serial Attached SCSI (SAS), and even solid state PCIe drives.  As powerful as the new LGA 2011 processors are, they retain much of the energy savings features of Sandy Bridge, except for the internal graphics.  Thus, when you’re not pushing the processor to the limit, it sips very sparingly from the electrical outlet.  If only the same could be said for graphics cards, which will be the big power hogs in any X79 system, but I suspect that performance computer users, CAD designers, 3D modelers, PC gamers, etc. won’t really care how much power their systems are using. 

Processor Data for Typical X58, Z68 and X79 Systems

Chipset X58 Z68 X79
Processor Core i7 - 980 (Gulftown) Core i7 - 2700 K (Sandy Bridge) Core i7  - 3930K (Sandy Bridge - E)
Launch Date Q2 2011 Q2 2011 Q4 2011
Passmark CPU Score 10310 10420 14861
Number of Cores 6 4 6
Number of threads 12 8 12
Max Proc. Clock Speed 3.33 GHz 3.5 GHz 3.2
Max Turbo Clock 3.6 GHz 3.9 GHz 3.8
Support Chip Interface Quick Path Interconnect DMI DMI
Quick Path Interconnect Speed in GB/s each direction 9.6 NA NA
Direct Media Interface (DMI) Speed in GB/s each direction NA 2 2
Smart Cache Size 12 MB 8 MB 12 MB
Memory Channels 3 2 4
Memory Type DDR3 1066 DDR3 1333 DDR3 1600
Processor PCI Express 2.0 Lanes NA 16 40
Fabrication Process Type 32 32 32
Processor Max Thermal Design Point (W) 130 95 130
Processor Graphics NA Intel HD 3000 NA
Advanced Vector Extensions (AVX) no yes yes

I show the Passmark CPU benchmark score from their Performance Test 7 test suite for Windows in the table and on the next panel in a bar chart of many processor results.  The scores are a statistical average of all the Performance Test 7 results for a given processor that have been uploaded by users, and thus average out individual differences in results due to different motherboards and component selections. Passmark receives hundreds to thousands of such results for any given processor, and average results can be viewed at any time on the Passmark web site.  I wasn’t surprised to see the six core i7 3930K (Sandy Bridge E) score significantly better than the four core i7 2700K (Sandy Bridge) at 14861 vs. 10420, but I was surprised to see the 3930K trounce the six core i7 980 (Gulftown) which only scored 10310.  Sandy Bridge also introduced additional performance improvements in cache memory architecture and instruction set decoding which together with greater memory bandwidth may have given the newer 3930K the edge over the 980.

Chipset Data for Typical X58, Z68 and X79 Systems

Chipset X58 Z68 X79
IOH or PCH Product Number Intel AC82X58 IOH Intel BD82Z68 PCH Intel BD82X79 PCH
Fabrication Process Type (nm) 65 65 65
I/O Hub, Platform Controller Hub Max TDP (W) 24.1 6.1 7.8
Support Chipset PCIe 2.0 Lanes 36 on IOH + 6 on ICH 10 8 on PCH 8 on PCH
Direct Media Interface (DMI) From IO Hub to ICH 10, 1 GB/s each direction From processor to PCH, 2 GB/s each direction From processor to PCH, 2 GB/s each direction
QPI Link to IO Hub raw data rate in GB/s each way 9.6 (12.8 capable) NA NA
USB 2.0 Ports 12 on ICH 10 14 14
SATA 2.0 Ports 6 on ICH 10 4 4
SATA 3.0 Ports NA 2 2

As a high performance personal workstation, X79 seems to have much to recommend it, especially compared to older, less energy efficient multi-processor Xeon systems.  I’ve often wished Apple offered something between their ponderous Xeon based Mac Pro towers and their svelte but less powerful iMacs.  A new line of Mac Pros based on X79 would find an audience of power users and developers in the Mac community.

As a high performance gaming platform, the situation seems a little muddied.  Many of the early reviews I’ve read such as Anandtech, Legitreviews, and Guru3D found little performance difference between Sandy Bridge and its E successor.  As usual in game testing, the sole metric used is frames per second output capability of the game, which is often much higher than the typical display rate of 60 frames/sec.  This lack of performance difference was usually attributed to the fact that the graphics card limited performance (especially for DX 11), or that the game couldn’t make effective use of the extra processor cores of the SBE.  Even in SLI or Crossfire mode, SBE didn’t appear to do significantly better than SB in most tests.  Anand Lal Shimpi specifically pointed out that SLI performance doesn’t suffer from splitting the 16 PCIe lanes to make two X8 slots for Sandy Bridge based SLI.  Of course, X79 processors are capable of 3 way SLI, but the power requirements of such a system could be upwards of 1500 Watts, depending on the cards and system configuration.  Such a power supply can’t even use a standard NEMA three prong outlet, since the current draw exceeds the recommended limit of 15 amps for the outlet.  Not many people will want to rewire their house just so they can plug in their 3 way SLI system.   I suspect that most casual gamers will be perfectly happy with a Z68 based system, which is ironic since Intel’s PR hyped X79 as the ultimate gaming platform.  I was a little surprised at the lack of gaming performance differentiation between Sandy Bridge and Sandy Bridge E, and in our forthcoming X79 system review, I’ll revisit the issue of real world performance, including gaming performance both in SLI and non-SLI mode. 

To Upgrade or Not to Upgrade

The lack of significant gaming performance improvement over Sandy Bridge (Z68) left many reviewers damning X79 with faint praise.  Yes, X79 is faster and has more cores, yes it does SLI (or Crossfire), and yes it has higher memory bandwidth.  But there was no USB 3 or SAS on the PCH, and no internal graphics.  Shimpi even bemoaned the loss of Quick Sync, a feature of Sandy Bridge’s internal graphics which provides hardware acceleration for certain video processing tasks.  Some even wondered if the extra cores could be put to effective use, implying that apps that could make use of the full complement of virtual processors were few and far between.  Furthermore, most of the early reviews used the Core i7-3960X Extreme Edition processor and, not surprisingly, found its price rather steep at over US$ 1000 vs. under US$ 600 for the Core i7-3930K, which performs almost as well as the extreme version. One came away from the reviews feeling that if one already owned a Sandy Bridge machine, either desktop or mobile, there was little to be gained from X79. 

As always, the question of whether to upgrade depends on where you’re upgrading from.  Upgrading to the next generation chipset/processor almost never provides enough performance gain to justify the cost, in my view.  I like to see roughly a factor of 2x broad performance improvement in the platform before I’ll upgrade, and this usually requires skipping a generation or two.  Thus, if you own either an X58 or Z68 platform, I would recommend a processor upgrade if available rather than an upgrade to X79.  If you own one of the previous generation chipset platforms such as X48, this is probably the right time to upgrade.  You still have a choice between Z68 (or one of the other Sandy Bridge chipsets) and X79, and either could be right depending on your needs.  If you tend to use your computer with only a single monitor, then Z68 is probably the right choice.  The platform as a whole is less expensive and saves electrical energy.  If you tend to use more than one monitor, then X79 is the better choice from a performance standpoint, since the internal graphics processing of Sandy Bridge won’t do you any good (with the exception of Quick Sync), but the extra pair of processing cores will. 

The reservations that some reviewers have expressed about apps or games not being able to use the full complement of 12 virtual cores seems a little misdirected.  There is an application that all users have that fully employs all available cores, namely the operating system itself, whether Windows, Linux, or Mac OS X.  With 8 or 12 virtual cores available, running more apps in parallel becomes possible and useful, especially for computing intensive tasks that would have tied up earlier generations of quad core processors for extended periods.  Of course, how well this works in practice depends on the ability of the OS to manage all its threads effectively and prevent bottlenecks, a subject we’ll take up again in our forthcoming X79 system review. 

 Next Up: Ivy Bridge

When contemplating a platform upgrade, it’s useful to consider what’s in Intel’s pipeline.  Lately there’s been a lot of leaked data about Ivy Bridge, the successor to Sandy Bridge.  In effect, Ivy Bridge is Sandy Bridge on a new 22 nm process, so power consumption is even lower.  Ivy Bridge i7 processors will get a next generation HD 4000 internal graphics processor, and like Sandy Bridge, be limited to 4 physical cores (8 virtual).  Accompanying the new processor line will be a new PCH, with support for USB 3.0 and, some claim, Thunderbolt as well.  If your upgrade choice is leaning towards Sandy Bridge, Ivy Bridge might be worth the wait.  It’s due out in the Spring of 2012. 

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    Chipsets Evolve
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    CPU Surprise
  • 6.
    Passmark Scores
  • 7.
    Chipset Data
  • 8.
    Gaming Platform?
  • 9.
    Upgrade or Not?
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