Intel's Haswell Architecture Analyzed: Building a New PC and a New Intel
by Anand Lal Shimpi on October 5, 2012 2:45 AM ESTWhen I first started writing about x86 CPUs Intel was on the verge of entering the enterprise space with its processors. At the time, Xeon was a new brand, unproven in the market. But it highlighted a key change in Intel's strategy for dominance: leverage consumer microprocessor sales to help support your fabs while making huge margins on lower volume, enterprise parts. In other words, get your volume from the mainstream but make your money in the enterprise. Intel managed to double dip and make money on both ends, it just made substantially more in servers.
Today Intel's magic formula is being threatened. Within 8 years many expect all mainstream computing to move to smartphones, or whatever other ultra portable form factor computing device we're carrying around at that point. To put it in perspective, you'll be able to get something faster than an Ivy Bridge Ultrabook or MacBook Air, in something the size of your smartphone, in fewer than 8 years. The problem from Intel's perspective is that it has no foothold in the smartphone market. Although Medfield is finally shipping, the vast majority of smartphones sold feature ARM based SoCs. If all mainstream client computing moves to smartphones, and Intel doesn't take a dominant portion of the smartphone market, it will be left in the difficult position of having to support fabs that no longer run at the same capacity levels they once did. Without the volume it would become difficult to continue to support the fab business. And without the mainstream volume driving the fabs it would be difficult to continue to support the enterprise business. Intel wouldn't go away, but Wall Street wouldn't be happy. There's a good reason investors have been reaching out to any and everyone to try and get a handle on what is going to happen in the Intel v ARM race.
To make matters worse, there's trouble in paradise. When Apple dropped PowerPC for Intel's architectures back in 2005 I thought the move made tremendous sense. Intel needed a partner that was willing to push the envelope rather than remain content with the status quo. The results of that partnership have been tremendous for both parties. Apple moved aggressively into ultraportables with the MacBook Air, aided by Intel accelerating its small form factor chip packaging roadmap and delivering specially binned low leakage parts. On the flip side, Intel had a very important customer that pushed it to do much better in the graphics department. If you think the current crop of Intel processor graphics aren't enough, you should've seen what Intel originally planned to bring to market prior to receiving feedback from Apple and others. What once was the perfect relationship, is now on rocky ground.
The A6 SoC in Apple's iPhone 5 features the company's first internally designed CPU core. When one of your best customers is dabbling in building CPUs of its own, there's reason to worry. In fact, Apple already makes the bulk of its revenues from ARM based devices. In many ways Apple has been a leading indicator for where the rest of the PC industry is going (shipping SSDs by default, moving to ultra portables as mainstream computers, etc...). There's even more reason to worry if the post-Steve Apple/Intel relationship has fallen on tough times. While I don't share Charlie's view of Apple dropping Intel as being a done deal, I know there's truth behind his words. Intel's Ultrabook push, the close partnership with Acer and working closely with other, non-Apple OEMs is all very deliberate. Intel is always afraid of customers getting too powerful and with Apple, the words too powerful don't even begin to describe it.
What does all of this have to do with Haswell? As I mentioned earlier, Intel has an ARM problem and Apple plays a major role in that ARM problem. Atom was originally developed not to deal with ARM but to usher in a new type of ultra mobile device. That obviously didn't happen. UMPCs failed, netbooks were a temporary distraction (albeit profitable for Intel) and a new generation of smartphones and tablets became the new face of mobile computing. While Atom will continue to play in the ultra mobile space, Haswell marks the beginning of something new. Rather than send its second string player into battle, Intel is starting to prep its star for ultra mobile work.
Haswell is so much more than just another new microprocessor architecture from Intel. For years Intel has enjoyed a wonderful position in the market. With its long term viability threatened, Haswell is the first step of a long term solution to the ARM problem. While Atom was the first "fast-enough" x86 micro-architecture from Intel, Haswell takes a different approach to the problem. Rather than working from the bottom up, Haswell is Intel's attempt to take its best micro-architecture and drive power as low as possible.
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Kevin G - Saturday, October 6, 2012 - link
Losing just the MacBook AIr isn't going to hurt Intel much as a whole but it is doubtful that Apple would just move that product line to ARM. The rest of the line up would likely follow. The results by the numbers would hurt Intel but nothing to doom the company. Intel does have the rest of the PC industry to fall back upon... except the PC market is shrinking.Apple is one of Intel's best gateway into the ultra mobile market. Apple has made indications that they want to merge iOS and OS X over the long term which would likely result in dropping either ARM or x86 hardware to simplify the line up.
WinRT is also a threat to Intel and
Kevin G - Saturday, October 6, 2012 - link
(Hrm... got cut off there)WinRT is also a threat to Intel but WinRT has next to zero market share. The threat here is any success it obtains. Apple on the other hand controls ~75% of the tablet market last I checked.
Andriod is a bit neutral to Intel as manufacturers can transition between ARM and x86 versions with relative ease. Intel will just have to offer competitive hardware at competitive prices here. The sub 10W Haswell parts are going to be competitive but price is a great unknown. The ARM SoC's are far cheaper than what Intel has traditionally been comfortable with. So even if Intel were to acquire all of the Android tablet market, it would be a minority at this time and over the short term (even in the best case scenario, it'd take time for Android based tablets to surpass the iPad in terms of market share).
So ultimately it would be best for Intel to snag Apple's support due to their dominant market share in the tablet space and influential position in the smart phone space.
andrewaggb - Friday, October 5, 2012 - link
Agree with others. Best Anandtech article I've read in a long time.Most articles lack the detail and insights that this one has.
mrdude - Friday, October 5, 2012 - link
Great article. Great depth, great info and very thorough. Hats off :)But I couldn't shake the feeling that I was missing perhaps the most important bit of information: price.
Obviously, Intel isn't going to give that away 9 months away from the presumed launch date -- though in typical fashion we'll see it leaked early. It still is the biggest question regarding Haswell's, and in turn Intel's, success against ARM.
I think most consumers are already at that good enough stage, where your Tegra 3 or Snapdragon S4 can fulfill all of their computing needs on a tablet or a phone. The biggest drawback for productivity purposes isn't necessarily the "lack of CPU performance" but rather the lack of a proper keyboard/mouse, gaming, along with a rare application or two that's still locked to x86 (Office rings a bell, though not for long). Or I should say, these were drawbacks. Not any longer.
So is Intel going to cut their margins and go for volume? Or are they just going to keep their massive margins and price themselves out of contention? Apple carries with itself a brand name that people want. It's become more than a gadget but a fashion accessory. People don't mind paying for Apple tax. I don't think I ever will, but at least I can notice the trend. The Intel brand doesn't carry with it the same cult following and neither does x86. Unless Intel is willing to compete with ARM on price, lowering the cost of their products below Apple's, I don't think think the substantial increases in efficiency and performance will matter all that much.
name99 - Friday, October 5, 2012 - link
"Sandy Bridge made ports 2 & 3 equal class citizens, with both capable of being used for load or store address calculation. In the past you could only do loads on port 2 and store addresses on port 3. Sandy Bridge's flexibility did a lot for load heavy code, which is quite common. Haswell's dedicated store address port should help in mixed workloads with lots of loads and stores."The rule of thumb numbers are, on "ordinary" integer type code:
1/6 instructions are branches
1/6 are writes
2/6 are reads
2/6 are ALU
This makes it more obvious why Intel moved as it did.
You want to sustain as close to 4ops/cycle as you can.
This means that your order of adding abilities should be exactly as Intel has done
- first two ALUs
- next two read/writes per cycle (ideal would be a mix of load/store) but Intel gave us that you can do a load+store per cycle
- next two loads per cycle
- next make sure the branches aren't throttled (because back-to-back branches are common, and you want branches resolved ASAP)
- next make the load-store system wide enough to sustain a MAC per cycle (two loads+store)
It's hard to see what is left to complain about at this level.
And of course we have better lock performance. So what's left?
What I think still have substantial room for improvement (correct me if I'm wrong) is
(a) TLB coverage
(b) TLB efficiency.
TLB coverage could be improved with a 2nd level TLB but (as far as I know) Intel doesn't go in for that, unlike POWER.
By TLB efficiency, I mean not needing to lose performance due to different address spaces. Unfortunately Intel seems screwed here. The POWER segment scheme (especially the 64-bit scheme) is REALLY powerful here in allowing multiple address spaces to coexist, so that multiple shared libraries, the main app code, IO, and memory mapped files, can all have persistent simultaneous TLB entries. (Note that this has nothing to do with the Intel segment scheme --- different technology, to solve a different problem.)
As far as I know, right now all Intel has is a single ASID representing a process. Better than no ASID, and having to flush the TLB on every context switch; but not especially good at sharing entries --- so (again as far as I know) shared libraries or shared mem-mapped files being used by multiple processes, even when they are mapped to the same address, have to have separate TLB entries, each one with a different ASID corresponding to the process calling them.
name99 - Friday, October 5, 2012 - link
Stupid me. I should have read the entire article. So we do have a (nicely sized 2nd level TLB).I guess my only remaining complaint now is that ASIDs are too coarse a tool.
In principle you could get dove some of the problems I mention using dedicated large pages for some particular purposes (eg to over the OS code and data, the equivalent of the frame buffer for modern windowing systems, and some pool of common shared libraries).
Does anyone know the extent to which both Windows and OSX actually make use of dedicated large pages in this way?
Peanutsrevenge - Friday, October 5, 2012 - link
Great article Anand, but when will Anand cloning be incorporated in CPU designs so we can all have one of you at home to pull out and extract information from @ will ? ?Although, with that said, I was already made aware of much of this recently from listening in to some random guys babbling about tech stuff on a podcast ;)
Rectified - Friday, October 5, 2012 - link
Anand, you write the best tech articles on the web. As a graduate student in computer engineering, I appreciate the practical yet technical analyses you write on the industry. Keep it up!Crazy1 - Friday, October 5, 2012 - link
I like the concept of Panel Self Refresh, yet I feel that Intel could implement this themselves. I'm not an expert, but couldn't a buffer be placed on the CPU package between the GPU and panel? This may not be as efficient as if the panel makers did it themselves and it would probably only work when using the IGP (when it would most likely have the greatest impact), but at least it is a step in the right direction.Additionally, Great Article! Anandtech provides some of the most thorough technology articles. Keep it up.
random2 - Saturday, October 6, 2012 - link
" If all mainstream client computing moves to smartphones,..........."Seriously? The idea of all mainstream computing done on nothing but smartphones seems to stretch the imagination just a bit much. There isn't even the most basic of businesses that do not have a computer (made with mainstream components as are most small and medium sized businesses) and business software. Don't forget the PC gamers and people who like larger viewing and typing surfaces. Or the fact that in eight years, home and business PC's will be blindingly fast with larger displays with much greater pixel density, possibly clear screen touch surfaces, likely alternative interfaces than just a keyboard and mouse and incredible computing and rendering power.
The likelihood of the general populace turning all their computing needs over to a palm size PC I see as kind of weird fantasy where people learn to love minute typing interfaces and squinting at hi density displays fit into 3.5by 4.5 inches for long periods of the day without interruption. No, to push the idea of micro computing one must discount all of the other advances in the computer/electronics industries in order to make their pet theory viable.