KarbosGuide.com. Module 3e.03

The second generation of Pentium II

The contents:

  • The Deschutes
  • 100 MHz Front Side Bus
  • The Original Celeron
  • The Over-clocking
  • The Good Celeron (the Mendocino)
  • The New Great Socket 370
  • Dual Celeron configuration
  • Next page
  • Previous page

  • The next Pentium II, the Deschutes

    The third P6 CPU was Intel's Pentium II code named "Deschutes". This new core also lead to the Celerons in various brands.

    On January the 26th 1998 Intel introduced the new 333 MHz model of Pentium II.

    It was the first of a second generation Pentium IIs known under the code name "Deschutes". The chips are produced with 0.25 micron technology, which reduces the power consumption by more than 50 % compared to the original Pentium II "Klamath" with its 0.35 micron technology. The core voltage is down from 2.8 to 2.0 Volt

    100 MHz Front Side Bus

    On April the 15th, 1998 Intel released the next line of Deschutes. The system bus had been increased to 100 MHz. This will internally be multiplied by the clock factors 3.5, 4.0 and (June 1998) 4.5, making the CPU run at 350, 400 and 450 MHz. These CPUs use the new chip set: 82440BX.

    So these Deschutes chips use two different motherboards:

  • LX-based for the 333 MHz version (5 X 66 MHz)

  • BX-based for the 350, 400, 450, and 500 MHz versions
    (with clock multipliers of: 3.5, 4.0, 4.5, and 5.0 X 100 MHz).

    Fast L2 cache RAM

    The L2 cache RAM has to be cooled down and it has to be fast:

    CPU Clock RAM type Controller
    333 and 350 MHz 5.5 ns S82459AC
    400 MHz 5.0 ns S82459AD
    450 MHz 4.4 ns S82459AD

    The Original Celeron

    Early 1998 Intel was having a hard time with the Pentium II which was pretty expensive. Many users bought the AMD K6-233, which offered very good performance at a moderate price.

    So Intel created a brand new CPU called Celeron. It is a Pentium II cartridge except for the L2 cache, which has been chopped away. It uses a 'Covington' core, and we could just as well have called it the Pentium II-SX. In 1998 Intel replaced their Pentium MMX with the first Celerons. Later the design was improved a lot, and Celeron became a very successful product.

    This first inexpensive Celeron cartridge fitted into Slot 1 and it ran on a 66 MHz system bus. The internal clock ran at 266 or 300 MHz and delivered good performance for floating point and MMX heavy programs such as certain games. Concerning office applications, the lack of L2 cache was a great disadvantage.


    The first Celeron were extremely good for over-clocking, since much of the problem here arises from the onboard L2 cache. The L2 cache RAM cannot function at high clock frequencies, but without L2 cache RAM this problem did not occur with the first Celerons.

    The Celeron 266 and 300 ran at speeds of 412 MHz and 464 MHz without any problems. However, for non-overclocking purposes the Celeron cartridge could not be recommended. Its lack of L2 cache was too big a disadvantage.

    Celeron with L2 cache - the Mendocino

    The next variant of Celeron got the code name Mendocino. First it came in 300 and 333 MHz versions.

    The interesting part is that the new cartridge holds 128 KB L2 cache inside the CPU itself. This gives very good performance, since the L2 cache runs at full CPU speed. Here you see a Celeron 300A. A chip on a card:

    Integrated L2 cache

    The manufacturing price was increased by less than 10%, adding the 128 KB integrated L2 cache, while the performance probably increased 30-40%. The number of transistors were increased from 7.5 million to 19 million due to the L2 cache.

    However, on-chip L2 cache is a good technology. In the first 0.25-micron technology, the Mendocino's 128K cache took up about 35 mm2 of die area. It added $10 to the manufacturing costs, but these numbers decreased going into 0.18 micron process technology. And then it is cheaper to produce a big integrated L2 cache than to add the chips to an expensive Slot 1 or 2 module.

    These early "Mendocino" cartridges were just as good as the traditional 66 MHz Pentium IIs. The Mendocino-based Celeron cartridge running at 300 MHz was named with an A as suffix to distinguish it from the Celeron 300 without L2 cache.

    Also good for over-clocking

    Hence, the first two models were the Celeron 300A and 333. They did very well, being priced very low compared to the equivalent Pentium IIs.

    In terms of over-clocking they proved successful as well. Here it appears that the 300A was the best. It works fine with a clock doubling of 4.5 X 103 MHz giving 464 MHz. The 333A model "only" runs at 416 MHz (5 X 83 MHz).

    Faster with Celeron

    On January 4th 1999, Intel introduced a 366 MHz version and a 400 MHz version both working the RAM on a 66 MHz bus. The clock multiplier within the new Celerons goes up to 8.0.

    March 15, 1999. The 433 MHz version of the Celeron was launched. A 466 MHz version was released late April.

    July 31, 1999. The 500 MHz version of Celeron was launched.

    Later 1999 the Celeron came in a 533 MHz version. In 2000 came 566 MHz Celerons produced with 0.18-micron process technology.

    New Socket 370 for the Celeron

    The 400 and 366 MHz processors were as all successors available in a plastic pin grid array (P.P.G.A.) form factor.

    This PGA370 socket looks quite like a traditional Socket 7. It holds 370 pins:

    Both are ZIF (Zero Insertion Force) sockets containing a lever so you can open and close the socket. This makes it very easy to insert the CPU.

    However, the PGA uses a different bus protocol (GTL+) than the Socket 7, which also only holds 238 pins. The GTL+ bus is the same protocol as all Pentium II's. Hence, they use the same chip sets.

    The socket 370 is cheaper to produce than Slot 1 cartridges, so all Intels mainstream processors will come in this design.

    The roadmap for the Celeron looks like this:

  • 66 MHz bus versions up to 800 MHz.
  • 100 MHz bus versions introduced in 2001, bringing the chip up to 1200 MHz.

    Dual Celeron configuration

    Using two Celerons on one motherboard could be a great idea. It would enable people to produce very inexpensive high-powered workstations. Windows NT is capable of using both processors.

    During 1998 I heard of several private persons, who made the Celerons work in dual SMP (symmetric multiprocessing) configurations. But in July 1999 two companies produce motherboards for dual Celeron configuration.

    Here is a little picture of such a board. You see two socket 370's:

    See Abits own homepage on the BP6 board. And see QDI.

  • Next page
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    Learn more

    Read about chip sets on the motherboard in module 2d

    Read more about RAM in module 2e

    Read module 5a about expansion cards, where we evaluate the I/O buses from the port side.

    Read module 5b about AGP and module 5c about Firewire.

    Read module 7a about monitors, and 7bon graphics card.

    Read module 7c about sound cards, and 7d on digital sound and music.

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