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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  • Sergio710 - Thursday, August 3, 2006 - link

    I've heard that Merom would come to 45 nm some day, does anyone know more about it ?

    supposed date ?
    impact on battery life ?
    Reply
  • mino - Thursday, August 3, 2006 - link

    All CPU series wiil go 45nm. Eventually.

    AFAIK don't expect 45nm Core 2's sooner that Q108.
    Reply
  • Sergio710 - Thursday, August 3, 2006 - link

    Forgive my ignorance, but what benefit will have 64 bits for every day use ?

    better performances on Vista or enabled soiftware or only the possibility to install more RAM ?
    Reply
  • LoneWolf15 - Friday, August 4, 2006 - link

    quote:

    Forgive my ignorance, but what benefit will have 64 bits for every day use ?

    better performances on Vista or enabled soiftware or only the possibility to install more RAM ?
    Longevity will be the benefit.

    It's not helpful right now, but if you're like me, you'd keep a notebook computer for some time before getting rid of it. I buy as future-proof (since that isn't possible, future-resistant) as I can. That means I'd want a 64-bit capable processor so that I can run the 64-bit version of Vista at some point, and so that I have the option of going to 4GB of RAM on my notebook some day. Since Merom prices are the equivalent of Yonah prices, this makes even more sense --it wouldn't cost me any more.
    Reply
  • Pandaren - Thursday, August 3, 2006 - link

    Right now, there is no benefit. Unless you are running Linux. 64-bit is completely useless for most people until Microsoft gets it together and finishes Windows Vista. Reply
  • peternelson - Thursday, August 3, 2006 - link

    I agree I was thinking of 64 bit linux and technical apps like rendering.

    However there is possible option on XP64 professional. eg if you want to do trial factoring for mersenne.org prime number project, running the 64 bit client gives a big boost over 32 bit version.

    I hope 64 bit becomes more mainstream (not just nerds) when Vista 64 is available.

    In ideal world: boot linux64 and Vista64 or virtualise one with the other.

    As a bonus if you can throw in a 64 bit version of a new Mac OS for a triple OS environment, that would be just what the doctor ordered.

    At the moment I can live without the Apple support, so linux/vista will be fine. ie Linux for serious work, Vista for 3D gaming.
    Reply
  • jeffwegher - Thursday, August 3, 2006 - link

    Isn't another advantage of the new Merom that it's 64-bit whereas the older Yonah is only 32-bit? Reply
  • peternelson - Thursday, August 3, 2006 - link

    He stole my comment, but ABSOLUTELY.

    A major disadvantage of Core Solo and Duo (as in Yonah) was that it's 32 bit ONLY.
    For that reason I won't buy a laptop or apple mac based around it.
    Merom (Core 2 Duo) IS 64 bit capable and that's important to me. It's the MOST important feature of this upgrade, second most important is virtualisation.

    I hope Apple wake up and start sticking Meroms into their desktop and notebook macs real soon.

    Also anandtech you don't mention that very point, using a so-called mobile cpu in a desktop SFF which is a market predicted to grow.

    This has to be another big market for Merom cpu: space saving home systems, media centres etc.

    As for all the hype about how much better this new generation architecture is, I have to say the performance jump of 2-5-10-15-20% is mediocre compared to what might have been expected if the reality lived up to the hype. Thanks anandtech for setting the record straight. On the other hand ANY performance increase for no extra battery usage has to be welcome. You're right that the FSB constraint limits it in today's machines.

    It's good they are priced similarly although in the market I expect manufacturers to charge a premium in the short term.

    How quickly will Apple be adopting this in their small desktop machines?
    Reply
  • IntelUser2000 - Saturday, August 5, 2006 - link

    quote:

    As for all the hype about how much better this new generation architecture is, I have to say the performance jump of 2-5-10-15-20% is mediocre compared to what might have been expected if the reality lived up to the hype. Thanks anandtech for setting the record straight. On the other hand ANY performance increase for no extra battery usage has to be welcome. You're right that the FSB constraint limits it in today's machines.

    It's good they are priced similarly although in the market I expect manufacturers to charge a premium in the short term.

    How quickly will Apple be adopting this in their small desktop machines?


    Actually you are in your own reality to expect greater advantage than that over Core Duo. If you have been actually paying attention, Intel expects 20% advantage for Core 2 Duo 2.33GHz over Core Duo 2.167GHz. Core 2 Duo's performance advantage of 40% applies against Pentium D, which is worse performer than Core Duo.

    Not to mention Core 2 Duo in Laptop has same FSB, same memory, same chipset as Core Duo!!
    Reply
  • Pandaren - Thursday, August 3, 2006 - link

    Intel claimed all along a 40% performance jump relative to Pentium D, NOT Core Duo. The performance jump relative to Core Duo was always claimed as "up to 20%," which is in line with Anandtech's findings. Reply

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