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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  • saleemi - Saturday, February 28, 2009 - link

    what is the difference between Dual Core and Core 2 Duo processor?
    I want to buy a laptop what i will do?
    Can some body please explain the difference..
    Reply
  • kem - Thursday, December 06, 2007 - link

    I have a notebook with a 940GML / Celeron 440. Can i upgrade to a CoreDuo FSB533? Reply
  • tatpeng - Sunday, December 02, 2007 - link

    Anand,

    I would like seek your advice. I want to buy laptop but i confused on the Centrino Duo Core 2 Duo and Intel Core 2 Duo. I looking at the Acer Aspire Laptop Centrino Duo Core 2 Duo and Compaq Presario Intel Core 2 Duo. So i would like to know the difference. Please assist. Both is Core2 Duo but the Acer is with Centrino. Is Acer better or Compaq better?
    Reply
  • a rabbit - Wednesday, August 30, 2006 - link

    Hi,

    A few questions:

    (1) Can we assume that the power draw numbers represent the best possible performance one can expect from Core 2 Duo mobile systems one can purchase today, or, should we assume that they represent typical performance, or, can we say we don't know because we only used one sample of Core 2 Duo?

    (2) What about the Core Duo (Yonah)? Theoretically, if Intel supplied all CPUs to the reviewer, I as Intel would supply the best quality (lowest power draw) Core 2 Duo, and the worst quality (highest power draw) Core Duo for my reviewer to perform the review on.

    Thanks!

    -a rabbit
    Reply
  • chetech - Friday, August 11, 2006 - link

    Can a Core 2 Duo processor be fitted into an Apple Mac Mini using their new Intel Core Duo processors? Reply
  • wimh - Thursday, August 10, 2006 - link

    quote:

    one of the funny things about performance and battery life is that if you can complete a task quickly enough thus returning your CPU to an idle state faster, battery life will grow even though instantaneous power consumption may be higher.


    Actually this is not correct: a CPU that's clocked higher also needs a higer voltage. Therefore, doing the same amount of work faster will require more energy than spreading it out over a longer time (in theory).
    For this to be true in practice, you'll off course need to factor other things into account, like I/O-devices (which may have less choice in sleep states: keeping the hard disk spinning for a longer time can destroy the gain you had by slowing down the CPU), etc...
    Reply
  • devilzangel - Tuesday, August 08, 2006 - link

    .
    "Eventually" we will have processors based on light particles vs electrons; but that is "eventually"; lets talk about the very near mobile future shall we (1 year).

    1. EM64T enabling - Will DEFINATELY boost and widen the performance gap b/w Core D & Core2 D. Especially with the Vista 64bit OS system installed. EVEN when u run 32bit applications on it.

    2. Quad-Core 'Santa Rosa' - Another great stride by Intel to boost performance (of course at the expense of battery life (which i might add, shouldnt matter much since most laptop users use the laptop near AC outlets). I am definately going to wait until next year to upgrade to a new laptop. Plus Vista will take advantage of the extra cores.

    3. FSB, and Battery Life - Comon, lets not fool ourselves; Intel can full well come out with a 1066 config for mobiles WHENEVER they want. AND mobile MOBO can be fabricated to take advantage of it JUST as fast. BATTERY life is the ONLY culprit. I would be the FIRST to buy such a laptop. Why use a clumsy desktop with so much wattage when you can get slightly less performance with much better gains to offset the balance regardless. Lets get one thing straight ... Desktops are losing ground, Laptops are the future.

    4. Shared L2 Memory Cache - The 1st Core D processors were CRUDE at best in this regard. Core 2 D Proc.s will SHARE the FULL L2 cache.

    Ehh who knows what will happen in 2008, and 2009 .. IBM and Georgia Tech's 300GHZ (room temperature) processors may be producable by that time ..

    Sometimes, I feel as if the corporate giants stagger the new technology into consumer hands in stages so that they may reap the profits.

    devilzangel
    Reply
  • ViperV990 - Tuesday, August 08, 2006 - link

    Regarding the FSB vs battery life issue, can't they just throttle the FSB dynamically like they do with the multiplier? I mean, come on, I've been able to change the FSB speed on the fly using software since like what, the Celeron 300A days?

    (Forgive me if that was possible earlier. My earliest overclocking experience was with a Klamath P II 266...)
    Reply
  • devilzangel - Tuesday, August 08, 2006 - link

    In the older processors and mobos it may have been easier to access this code settings to allow HIGHER speeds than mentioned limits ..

    normal throttling of CPU, Cache, FSB, Fanspeed etc, is part of the architecture (or so i understand it to be) .. 'Over'throttling the FSB is something i am unsure of .. at best it is a risk.

    recently though, most (if not almost all) boards have such options blocked or hidden in Bios settings and chip configurations (except the higher end GA, Asus, DFI, Abit boards).. ofcourse it very possible (and it wouldnt surprise me if it is) that the Core 2 D are ALREADY capable of 1066FSB but the chips have been locked onto 667, or 800 (the architecture of the C2D desktop chips is pretty much identical to the meroms, almost); it is possible that such mobile settings may be unstable if someone managed to crack the coding and change the frequency settings. The causes could range from MOBO coding chips, to Heat issues

    It is kind of like apple; we the consumers found out around the beginning of this year that Apple always had a somewhat working version of their OS for intel hardware settings.

    remember the technology staggering .. the FSB is part of it. It is like Diamonds, and Oil; limit the supply of higher and faster technology to increase the chances of a higher profit history overall.

    devilzangel
    Reply
  • IsLNdbOi - Monday, August 07, 2006 - link

    I've got a Toshiba U205-S5002 which has a 945GM chipset. This article says that the 945GM supports Core 2 Duo. I need to find out now if the processor in my laptop has a PGA Socket-M or BGA CPU. I've checked Toshiba's support pages, but can't find any info. regarding the CPU's interface w/ the mobo.

    Anyone have any info. regarding the U205-S5002's CPU interface?
    Reply

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