The Return of Hyper Threading

While Nehalem is designed to scale to up to 8 cores per chip, each one of those cores has the hardware necessary to execute two threads simultaneously - yep, it's the return of Hyper Threading. Thus our quad-core Nehalem sample appeared as 8 logical cores under Windows Vista:


Four cores, eight threads, all in a desktop CPU

Note that as in previous implementations of Hyper Threading (or other SMT processors) this isn't a doubling of execution resources, it's simply allowing two instruction threads to make their way down the pipeline at the same time to make better use of idle execution units. Having 8 physical cores will obviously be faster, but 8 logical (4 physical) is a highly power efficient way of increasing performance.

We took Valve's source-engine map compilation benchmark and measured the compile time to execute one instance (4 threads) vs. two instances of the benchmark. The graph below shows the increase in compilation time when we double the workload:

Valve Map Compilation Benchmark - 4 to 8 Thread Scaling

While the 2.66GHz Core 2 Quad Q9450 (Penryn) takes another 127 seconds to execute twice the workload, the 2.66GHz Nehalem only needs another 49 seconds. And if you're curious, this quad-core Nehalem running at 2.66GHz is within 20% of the performance of an eight-core 3.2GHz Skulltrail system. Equalize clock speed and we'd bet that a quad-core Nehalem would be the same speed as an 8-core Skulltrail here. The raw performance numbers are below:

Valve Map Compilation Benchmark 

We couldn't disable Hyper Threading so we reached the limits of what we were able to investigate here.

The Socket A Quick Path to Memory
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  • Jedi2155 - Saturday, June 07, 2008 - link

    Indeed, once the OEM's start demanding DDR3 for their system's due to Nehalem, we start seeing prices drop due economies of scale playing a greater part. Reply
  • RedFoxOne - Thursday, June 05, 2008 - link

    I am still waiting for Intel and Google to merge so with their combined powers they can take over the world!

    JT
    http://www.Ultimate-Anonymity.com">http://www.Ultimate-Anonymity.com
    Reply
  • 0g1 - Thursday, June 05, 2008 - link

    Dude, wtf ... "Intel managed to change the cache structure and introduce an integrated memory controller while making both significantly faster than what AMD managed despite a four-year headstart."

    Thats bs. True, they are significantly faster, but you're comparing something that comes out in 6 months to something thats been out for like 1 year. And when it does come out (in 6 months) Shangai should be close by. Die shrink, cache increase, Hyper Transport clockspeed increase, lower latencies, and DDR3. Your comparison was simply unfair and untrue (considering AMD's upcoming cache and memory structure looks to be faster).
    Reply
  • SiliconDoc - Monday, July 28, 2008 - link

    Well, in this, one always likes the top dog better - they supply the goodies so much more often (even by unendorsed leaked channels which is GREAT if you ask me), and in turn the monetary stream from the resultant forces, whatever they may be.
    Add in the hype, and someone always has a favorite, so there ya go.
    However, I find at least myself disappointed, since I don't have a grand every month to blow on new parts.
    I am over and over again just not impressed, single core HT still has a really good hold on everything ( the D805 is crisys friendly for sure), and the latest videocard wars have hammered through so many tiny jumps - over such a long period and massive price restructuring... I'm sure glad I've waited.. I keep setting up the purchase then some new chip hits... the timing is very difficult the last 8 months.
    This one appears to be another so what...again.
    If you keep adding 5% to 15% to wowzie 25%, three or four or five times in a row, you finally get to something that isn't disappointing.
    IMO they keep dribbling it out to us - maybe that's all they can do(OK I just LIED trying to be nice tothem), but they certainly spend an inordinate amount of time making 10 or 20 different "flavors" of all the chips, then they lock multipliers and disable catches...
    I agree with the guy who said maybe he'll get an E8400 when they're 50 bucks. I'm not running a University server / research cruncher / consulting firm system.
    Anyway good luck to AMD. Their Dx4/100 sample was exciting, as was their K6, good on their Thunderbird and Barton, no problem.
    They do it too now though, "unlock" their chips for $$$$.
    So, the whole system holds back FAST, and lays down SLOW to "saturate price point markets" and get everyone blowing their $$$ for some peice of hacked down crud. That's the way it IS.

    Reply
  • HexiumVII - Thursday, June 05, 2008 - link

    While AMD might not have a competitor anytime soon, lucky for us, Nvidia decided to go all ape bananas on Intel. General processors are really at a plateau for consumers. We really don't need 8 cores. What we do need is focused cores for Video and 3D. We are still pretty far from some really nice multimedia acceleration to finally kill our clunky mouse interface. Reply
  • 0g1 - Friday, June 06, 2008 - link

    We need all the cores we can get in CPU's. In the future, games are going to be multithreaded to the point of hundreds of threads.

    Focused cores for 3D should be a separate entity from the CPU die for maximum speed because:
    1. Main memory speed is too slow compared to graphics memory.
    2. 3D can be separated with little to no penalty, thus allowing you to get theoretically twice the speed via two processors (one for 3d and one for general computation).
    Reply
  • mkruer - Thursday, June 05, 2008 - link

    Compare the blue and yellow graph to Anand's two graphs. According to these benchmarks, "old" Penryn beats "new" Penryn by about 38% in single-threaded Cinebench and 17% in multi-threaded Cinebench.

    http://images.anandtech.com/graphs/nehalempreview_...">http://images.anandtech.com/graphs/nehalempreview_...
    http://images.anandtech.com/graphs/nehalempreview_...">http://images.anandtech.com/graphs/nehalempreview_...
    http://images.anandtech.com/graphs/amd%20phenom%20...">http://images.anandtech.com/graphs/amd%20phenom%20...
    http://www.anandtech.com/printarticle.aspx?i=3153">http://www.anandtech.com/printarticle.aspx?i=3153

    A mature Penryn system should score closer to the 3000 mark then what Anand listed.

    You can look at other review sites as well
    http://www.hardwarezone.com.my/articles/view.php?i...">http://www.hardwarezone.com.my/articles/view.php?i...
    http://www.overclockersclub.com/reviews/intel_q945...">http://www.overclockersclub.com/reviews/intel_q945...

    This should be raising some red flags people
    Reply
  • Anand Lal Shimpi - Thursday, June 05, 2008 - link

    That's a very good question, the Penryn system we ran the new numbers on is obviously different from the older systems but I'm trying to figure out now if there is a software explanation for why Cinebench is a lot slower now.

    The POV-Ray scores line up with what they were in our previous reviews, the only thing I can think of off the top of my head is that we've since switched to Vista SP1 and that has caused some problems where performance has gone down (see the 3dsmax scores).

    I'm digging on the Cinebench question right now and will post back as soon as I have some more data.

    -A
    Reply
  • Anand Lal Shimpi - Thursday, June 05, 2008 - link

    Just a quick check of the multithreaded numbers shows that the old and new Penryn numbers are where they should be, within 2%, so that's not an issue.

    Re-running the single threaded stuff now to see where we're at. Neither of the sites you pointed at used Vista SP1 either (including our older Phenom results), I may to run a quick install of Vista without SP1 to figure this one out.

    I'll keep you posted.

    -A
    Reply
  • Anand Lal Shimpi - Thursday, June 05, 2008 - link

    Fixed.

    That was entirely an error on my part, it wasn't a SP1 or a configuration issue. It was an Excel spreadsheet malfunction :) I used data from the wrong column (first run data vs. average run data) for Cinebench. Everything else looks to be exactly where it should be but I'll make another run through the spreadsheet to make sure.

    I just reran the numbers to confirm and now things make much more sense. Not only are our XCPU scores virtually identical to what they were for the Phenom article, but the single threaded tests make a lot more sense. Furthermore, the scaling from 1 to n-threads makes a lot more sense now too. Penryn gets a 3.56x speedup from multithreading while Nehalem gets a 4.18x speedup - the difference in scaling partially being due to HT.

    Thanks for bringing this to my attention and sorry for the mixup.

    Take care,
    Anand
    Reply

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