Core Duo vs. Core 2 Duo

We've spent a lot of time comparing Intel's Core architecture to NetBurst and AMD's K8; however, we've stayed away from quite possibly one of the most confusing comparisons: Core 2 Duo vs. Core Duo. 

Unlike its desktop predecessor, Core 2 Duo comes from the same genealogy as the Core Duo.  Despite the similarities in name and in architecture, there are some fairly major differences between the two CPUs, some of which won't become apparent until next year.  The table below should help summarize the differences:

  Core Duo (Yonah) Core 2 Duo (Merom)

Manufacturing Process

65nm

65nm

Die Size

90.3 mm^2

144.9 mm^2

Transistors

151M

291M

Clock Speeds

1.20GHz - 2.33GHz

1.06GHz - 2.4GHz+

FSB Frequency

533MHz - 667MHz

533MHz - 800MHz

L1 Cache Size

32KB + 32KB

32KB + 32KB

L2 Cache Size

2MB Shared

2MB - 4MB Shared

Pipeline Stages

12

14

Decoders

1 complex + 2 simple

1 complex + 3 simple

Maximum Decode Rate

3

4+1

Reorder Buffer

80

96

Issue Ports

5

6

Scheduling

Unified Reservation Station

Unified Reservation Station

Scheduler (# of Entries)

24

32

FP Units

FMUL/FADD:  1

FMUL:  1
FADD:  1
FSTORE:  1
FLOAD:  1

SSE Units

1

3

Integer Units

ALU:  2

AGU:  2

ALU:  3

AGU:  2

Load/Store Units

Load:  1

Store:  1

Load:  1

Store:  1

Socket Interface

Socket-M (PGA/BGA)

Socket-M (PGA/BGA) & Socket-P (PGA/BGA)

 

Compared to the desktop Core 2 Duo (Conroe), the mobile version is architecturally no different.  Obviously clock speeds (both CPU and FSB) are lower because these things will be going in notebooks where power consumption is more of a concern, but other than that the architectures are identical. 

Compared to Yonah, Merom has some very clear advantages; on the surface the larger L2 cache is responsible for the 140M increase in transistor count, but architecturally the improvements extend far beyond that.  You can get the details from the table above or from our previous articles on Intel's Core 2 processors, but simply put Merom is wider and slightly deeper than Yonah.  The slightly deeper pipeline helps increase clock speeds on Merom (which will bump performance a bit), but the added decode and execution width will increase overall performance.

Not listed in the table above are the improvements to the cache subsystem and memory accesses on Core 2 Duo.  Merom features more aggressive prefetchers than Yonah, as well as Intel's Memory Disambiguation technology that allows for out of order loads.  In other words, not only is Merom able to operate on more data at once, at a faster speed, but it can also get access to that data quicker. 

New CPU today, new platform in 2007

The first versions of Core 2 Duo are completely backwards compatible with the Napa platform that Core Duo currently uses, and thus they share the same Socket-M interface.  Unfortunately for Merom, Napa only supports a maximum of a 667MHz FSB and thus has almost 40% less bandwidth to the CPU than the desktop version, and is identical to what the fastest Yonah CPUs use.  The problem with FSB limiting Merom like this is that Merom is a hungrier core (as we've seen by the table above) than Yonah, so it needs a faster FSB in order to truly stretch its legs.  The tradeoff is that a faster FSB consumes more power, thus reducing battery life, not to mention that you'll need a "new" chipset to support the faster FSB. 

That new chipset is part of Intel's Santa Rosa platform, to be introduced in early 2007.  Santa Rosa is composed of Intel's upcoming Mobile 965 chipset, ICH8M and a new wireless solution with 802.11n support.  The new chipset will add official 800MHz FSB support, and thus Core 2 Duo processors released next year will be able to use the faster FSB.  The Santa Rosa platform also introduces a new pin-out, Socket-P, for Core 2 Duo processors.  Unfortunately that means you won't be able to use current Core 2 Duo and Core Duo processors in Santa Rosa based motherboards and notebooks. 

2007 Mobile Roadmap The Test Platform
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  • juanpoh - Friday, August 4, 2006 - link

    Looking at http://www.intel.com/products/processor/pentiumm/i...">Intel Pentium M link, only 915 and 855 chipset is supported. However 945 chipset is listed as supported in http://www.intel.com/products/processor/celeron_m/...">Intel Celeron M link. Reply
  • jaybuffet - Friday, August 4, 2006 - link

    I have the nx9420 notebook with the 945pm chipset... i was on hp support yesterday, and they said they would not support upgrading the CPU.. does that mean i am SOL because they wont upgrade the BIOS to support it? Reply
  • Pjotr - Friday, August 4, 2006 - link

    Please correct the percentage numbers on http://www.anandtech.com/cpuchipsets/showdoc.aspx?...">http://www.anandtech.com/cpuchipsets/showdoc.aspx?...

    "17.5% increase in performance" -> "17.5 % less time used" OR "21.3 % increaase in performance"

    Same mistake for all other time based benchmarks.
    Reply
  • shecknoscopy - Thursday, August 3, 2006 - link

    Given the nearly identical architectures of the desktop Conroes and the new Merom chips - how well do all of you think the two would stack up in a direct side-by-side comparison? This is open to blatant conjecture, of course, as the necessary hardware to <b>really</b> make a single-variable experiment isn't out there. But for those of us considering mobile-on-desktop options, how much of a performance cut would we see jumping from a Conroe to a Merom? Reply
  • IntelUser2000 - Saturday, August 5, 2006 - link

    quote:

    Given the nearly identical architectures of the desktop Conroes and the new Merom chips - how well do all of you think the two would stack up in a direct side-by-side comparison? This is open to blatant conjecture, of course, as the necessary hardware to <b>really</b> make a single-variable experiment isn't out there. But for those of us considering mobile-on-desktop options, how much of a performance cut would we see jumping from a Conroe to a Merom?


    Intel mentioned something about having different prefetchers that match the market, meaning Woodcrest's Prefetchers are fit for workstation/server, Conroe for desktop, Merom for mobile applications(performance/battery life).

    If you look at Core Extreme X6800 vs. Core 2 Duo E6700 benchmarks, you can see that in some reviews the differences are greater than the 267MHz clock difference(10% clock difference). Maybe Core Extreme has superior prefetchers to the Core 2 Duos, giving advantage in select few applications.
    Reply
  • Sunrise089 - Thursday, August 3, 2006 - link

    This was the exact question I just signed on to ask....so I await and answer as well. Reply
  • shecknoscopy - Thursday, August 3, 2006 - link

    Woohoo! Great minds think alike, eh? Also, so do ours! Reply
  • JackPack - Thursday, August 3, 2006 - link

    Which stepping did you use in this test? B1? Reply
  • EagleEye - Thursday, August 3, 2006 - link

    I think the asus barebones configuration is mislabeled in this article. The s96j has the WXGA 1280x 800 screen while the z96j has the WSXGA 1680x 1050 screen. They either had an s96j or the native resolution is wrong as they stated it. Reply
  • Kalessian - Thursday, August 3, 2006 - link

    I noticed that, too. Reply

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