Intel's Haswell Architecture Analyzed: Building a New PC and a New Intel
by Anand Lal Shimpi on October 5, 2012 2:45 AM ESTPrioritizing ILP
Intel has held the single threaded performance crown for years now, but the why is really quite easy to understand: it has prioritized extracting instruction level parallelism with every generation. Couple that with the fact that every two years we see a "new" microprocessor architecture from Intel and there's a recipe for some good old evolutionary gains. The table below shows the increase in size of some major data structures inside Intel's architectures for every tock since Conroe:
| Intel Core Architecture Buffer Sizes | ||||||
| Conroe | Nehalem | Sandy Bridge | Haswell | |||
| Out-of-order Window | 96 | 128 | 168 | 192 | ||
| In-flight Loads | 32 | 48 | 64 | 72 | ||
| In-flight Stores | 20 | 32 | 36 | 42 | ||
| Scheduler Entries | 32 | 36 | 54 | 60 | ||
| Integer Register File | N/A | N/A | 160 | 168 | ||
| FP Register File | N/A | N/A | 144 | 168 | ||
| Allocation Queue | ? | 28/thread | 28/thread | 56 | ||
Increasing the OoO window allows the execution units to extract more parallelism and thus improve single threaded performance. Each generation Intel is simply dedicating additional transistors to increasing these structures and thus better feeding the beast.
This isn't rocket science, but it is enabled by Intel's clockwork fab execution. Designers can count on another 30% die area to work with every 2 years, so every 2 years they increase the size of these structures without worrying about ballooning the die. The beauty of evolutionary improvements like this is that when viewed over the long term they look downright revolutionary. Comparing Haswell to Conroe, the OoO scheduling window has grown by a factor of 2x, despite generation to generation gains of only 14 - 33%.
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CaptainDoug - Friday, October 5, 2012 - link
Quite the read. Very informational. Anandtech has some of the best tech writers. True online journalism. Sometimes i miss that while reading tech blogs... You guys are a cut above.. at least one.colonelclaw - Friday, October 5, 2012 - link
Couldn't agree more, this article really brightened up what was otherwise a pretty miserable afternoon here in London.When am I going to be able to walk into a shop and buy something with Haswell inside it? Next March maybe?
Kepe - Friday, October 5, 2012 - link
As stated in the article, Haswell is coming in the summer of 2013.linuxlowdown - Saturday, October 6, 2012 - link
Tag team Intel fanboy puke.Azethoth - Sunday, October 7, 2012 - link
How do I downvote stupid crap like this "Tag team Intel fanboy puke." comment so that collectively we can see high quality comments without having to wade through the interturds as well? It really takes away from the best article I have read in a long time. Not because it is about Intel, but because it is about the state of the art.medi01 - Tuesday, October 9, 2012 - link
Well, I'd also ask how do I downvote stupid butt kissing like OP, while we are at rating....Kisper - Saturday, October 20, 2012 - link
Many people enjoy well written and informative articles. Are you telling me that if you wrote, you would not enjoy positive feedback from your readers?CaptainDoug - Tuesday, October 23, 2012 - link
Exactly.actionjksn - Sunday, October 7, 2012 - link
Why are you even on this article dumb fuck? I'm sure there is something that is of interest to you on the internet somewhere.medi01 - Tuesday, October 9, 2012 - link
Not sure about him, but I've looked into this article to figure power targets for haswell (especially interesting to compare to ARM crowd), NOT to read orgasmic comments about eternal wizdom of Intel's engineering...