Introduction
Core Duo (formerly known by its codename, Yonah) is the first dual-core Intel CPU targeted to the mobile market, i.e. inside it there are two complete CPUs. Curiously it is also the first Intel processor to be adopted by Apple Computer. In this tutorial we will present the main features of Core Duo and a table with all models released to date.
Core Duo is, in fact, a Pentium M with two cores and manufactured using 65-nm process (Pentium M is manufactured using 90 nm process)..
Even though it has two CPU cores inside the same package, Core Duo die size is almost the same of Pentium M’s (Dothan die). This means that the cost for manufacturing Core Duo is practically the same of Pentium M, which has just one core. Core Duo has 151.6 million transistors occupying an area of 90.3 mm2 (0.14 sq inch) while Pentium M based on Dothan die has 140 million transistors on an 87.66 mm2 (0.135 sq inch) area. Keep in mind that Core Duo is manufactured under 65-nm process while Pentium M is manufactured under 90 nm one.
Core Duo’s L2 memory cache is of 2 MB shared between its cores (Intel calls this shared L2 implementation “Smart Cache”). On Pentium D 840, for instance, which is a dual-core CPU, its 2 MB L2 memory cache is split between the cores, so each core has access to only 1 MB each. I.e. on Pentium D there are two 1 MB L2 memory caches, one per core. On Core Duo there is only one 2 MB L2 memory cache, which is shared between the two cores.
With a shared memory cache, the amount of memory cache that each core uses isn’t fixed. With a 2 MB L2 memory cache one core may be using 1.5 MB and the other 512 KB (0.5 MB) at a given moment, for example. If on a dual-core CPU with separated L2 memory cache one of the cores run out of cache (i.e. its 1 MB is being fully used) it needs to go directly to the slow RAM memory to fetch the required data, slowing down the system performance. On CPUs with shared L2 memory cache, each core can simply resize the amount of L2 memory cache it is using.
Another advantage of shared L2 memory cache is that if one core fetched a data (or a instruction) and stored it on the L2 cache, the other core can use this same piece of information. In dual-core CPUs with separated memory caches the second core would have to grab this data (or instruction) thru the CPU local bus, i.e. “from outside”, using the local bus clock, which is far inferior than the processor internal clock, thus slowing down the system performance.
Core Duo main features are the following:
• Dual-core technology
• Code-name: Yonah
• 151.6 million transistors occupying an area of 90.3 mm2 (0.14 sq inch)
• 32 KB L1 instruction cache and 32 KB data L1 cache
• 2 MB L2 memory cache shared between the two cores
• Socket 479
• 65 nm manufacturing process
• 667 MHz external bus (166 MHz transferring four data per clock cycle).
• SSE3 instruction set support
Centrino vs. Centrino Duo
We can break down Centrino platform into three families. The first family uses a Pentium M processor, Intel 855 or 915 Express chipsets and Intel PRO/Wireless LAN networking. The second family uses a Core Solo processor (which is a single-core version of Core Duo – so far only one Core Solo model was released, T1300, running at 1.6 GHz internally and at 667 MHz externally, 2 MB L2 cache and a TDP of 27 W), Intel 945 Express chipset and Intel PRO/Wireless 3945ABG networking. The third family, also known as Centrino Duo (and formerly known as Napa), uses Core Duo processor, Intel 945 Express chipset and Intel PRO/Wireless 3945ABG networking.
A laptop computer can only be called Centrino if it has the CPU, the chipset and the network adapter listed. If a given laptop is based on Pentium M but doesn’t have an Intel/PRO wireless adaptor it can’t be called Centrino. The same thing goes for Centrino Duo. A laptop can only be called Centrino Duo if it has a Core Duo CPU, a Intel 945 Express chipset and a Intel PRO/Wireless 3945ABG network adaptor.
Centrino Platform Families
Plataform Centrino Duo Centrino Centrino
Processor Core Duo Core Solo Pentium M
Chipset Intel 945 Expres Intel 945 Express • Intel 855
• Intel 915 Express
Networking Intel PRO/Wireless 3945ABG Intel PRO/Wireless 3945ABG • Intel PRO/Wireless 2100
• Intel PRO/Wireless 2200BG
• Intel PRO/Wireless 2915ABG
Core Duo Models
On the table below you will find all Core Duo models released so far. As you can see, the maximum power (TDP, Thermal Design Power) of the models starting with a “T” if of 31 W, while the maximum power of the models starting with an “L” is of 15 W.
Just put Core Duo spec in perspective, Turion 64 ML-44 model, which this the AMD CPU targeted to the mobile market having just one core, has a TDP of 35 W.
Model Internal Clock TDP
T2600 2.16 GHz 31 W
T2500 2 GHz 31 W
T2400 1.83 GHz 31 W
T2300 1.66 GHz 31 W
L2400 1.66 GHz 15 W
L2300 1.50 GHz 15 W
