Celeron

A Celeron is any of a large number of different budget x86 microprocessors produced by Intel and marketed as a second line to complement their more expensive but higher-performance Pentium CPUs. The first Celeron was introduced in August 1998 and based on the Pentium II. Later versions are based on the Pentium III and Pentium 4 designs.

The Celeron product concept was introduced by Intel in response to the company's loss of low-end market share, in particular to Cyrix's 6x86 and AMD's K6, but also to other competers such as the IDT Winchip. Intel's venerable Pentium MMX was no longer performance competitive and although a faster Pentium MMX would be cheap to make and technically straightforward, Intel preferred to move away from the industry standard Socket 7 platform (as competitors made drop-in replacements) and produced a budget part that was pin-compatible with their high-end Pentium II product (Slot 1). Due to patenting, competitors had difficulty making Slot 1 parts.

P6 Class Celerons

Covington

The first Celeron (codenamed Covington) was essentially a 266MHz Pentium II manufactured without any secondary cache at all. Although clocked at 266 or 300MHz (substantially higher than the old Pentium MMX), the cacheless Celerons were a good deal slower than the parts they were designed to replace. A substantial number were sold on first release, largely on the strength of the Intel name, but it quickly achieved a poor reputation both in the trade press and among computer professionals. Many people referred to it unkindly but accurately enough as the Slugeron. The initial market interest faded rapidly in the face of its poor performance and with sales at a very low level and being a market failure, Intel felt obliged to develop a substantially faster replacement as soon as possible.

Mendocino

Intel were well aware of the poor reputation of the original Celeron, and determined not to make the same mistake twice, with the result that the new Mendocino core Celeron was an excellent performer from the outset. Indeed, most industry analysts regarded the first Mendocino-based Celerons as too successful: performance was sufficiently high to not only compete strongly with rival parts, but also to attract buyers away from Intel's high-profit flagship, the Pentium II.

The key to the new Celeron's performance was cache. Where the old model had no secondary cache at all, the new part included 128KB of L2 cache as part of the chip itself. Otherwise, it was identical. With a total of 19.2 million transistors (including cache) on a single chip, the Mendocino Celeron was difficult and expensive to manufacture, but manufacturing excellence had always been an Intel strength and the company managed a flawless execution of a very ambitious project.

The first Mendocino-core Celeron was clocked at a modest 300MHz but was almost twice as fast as the old cacheless Celeron at the same clockspeed. To distinguish it from the old model, Intel called it the Celeron-A. Technically, the other Mendocino Celerons (the 333MHz part, for example) were simply Celeron, although people often call all Mendocino processors regardless of speed Celeron-A

The Mendocino Celeron was the first mass-market CPU to utilise on-chip L2cache. On-chip cache is difficult to manufacture; especially L2 as more of it is needed to attain a adequate level of performance. A benefit of on-die cache is that it can be made to run much faster than individual off-chip cache chips. Contrast this with the other common cache arrangements at that time. Most CPUs used mainboard mounted or slot mounted secondary L2 cache, which was very easy to manufacture, cheap, and simple to enlarge to any desired size. Typical cache sizes were 512KB to 1MB, typical speeds 66 to 100MHz. The Pentium II had a pair of moderately high-speed L2 cache chips mounted on a special-purpose board alongside the processor itself. This was expensive and imposed practical cache-size limits, but allowed it to be clocked faster. Typical size was 512KB, always running at 1/2 of the processor speed. The new Mendocino Celeron had only 128KB of cache, but ran it at full clock speed: typically 300MHz.

Although the Mendocino Celeron cache was rather small, its high clock speed more than overcame that handicap, and the Mendocino Celeron was an immediate success, particularly with the enthusiast market. Overclockers soon discovered that, given a high-end motherboard, the Celeron-A/300 could run reliably at 450 MHz. This was achieved by simply increasing the Front Side Bus speed from the stock 66 MHz to the 100 MHz spec of the Pentium II. At this speed, the Mendocino Celeron rivaled the fastest x86 processors in the world.

Over time, newer Mendocino processors were released at 333, 366, 400, 433, 466, 500, and 533 MHz. They all ran on the 66 MHz FSB, which was not a particular issue with the 300, but became a major limitation with the faster-clocked parts, and Mendocino Celerons from about 433MHz upwards were competitive rather than outstanding.

The Mendocino Celerons also introduced new packaging. When the Mendocinos debuted they came in both a Slot 1 and Socket 370 PPGA package. The Slot 1 form had been designed to accommodate the off-chip cache of the Pentium II and had mounting problems with motherboards. Because all Celerons are a single-chip design, however, there was no reason to retain the slot packaging for L2 cache storage, as there was none and Intel decided to discontinue the Slot 1 variant. Beginning with the 466 MHz part; onwards; only the PPGA Socket 370 form was offered. (Third-party manufacturers made motherboard slot-to-socket adaptors (nicknamed a slocket) available for a few dollars, which allowed, for example, a Celeron 500 to be fitted to a slot-equipped motherboard.)

The Mendocino also came in a mobile variant, with speeds from 266, 300, 333, 366, 400, 433, and 466 MHz.

Coppermine-128

The next generation Celeron was the Coppermine-128 (sometimes known as the Celeron II). These were a derivative of Intel's latest high-end part, the "Coppermine" Pentium III and were released in March 2000. Like the Mendocino, the Celeron-128 used 128KB of on-chip L2 cache and was restricted to a 66MHz bus speed. It was identical to the Pentium III except for the smaller secondary cache, the slower bus.

Although in theory the Celeron-128 had an updated core, the benefit of this was not noticeable. The Celeron was, by this time, the only mainstream CPU still using a 66 MHz bus and running 66MHz RAM, and was significantly slower than any major competitor. Sales gradually dwindled as the industry moved on and, although making a 100MHz bus version would have been a trivially easy task, Intel chose not to—probably because they had major production problems at that time and preferred to concentrate available resources on trying to ship sufficient volumes of the higher-margin Pentium III.

All Coppermine-128s were produced in the same FCPGA Socket 370 format that most Coppermine Pentium IIIs used. These Celerons started at 533 MHz and continued through 566, 600, 633, 666, 700, 733, and 766 MHz. Because of the limitations of the 66 MHz bus, there was very little performance difference between the higher-clocked models. So long as the major competition was the elderly AMD K6-2 this was acceptable. In July 2000, however, AMD released their Athlon-derived Duron—a budget CPU with a faster bus and larger caches. The Celeron-128 became almost as uncompetitive as the original "Sluggeron" had been.

On January 3, 2001, Intel finally switched to a 100MHz bus, and the performance improvement was startling. Although the Celeron 800 (the first of the 100MHz bus parts) was still less powerful than the Duron, it was within a few percent and a perfectly viable option. All Celeron-128s from the 800 up used the 100 MHz Front side bus. Various models were made at 800, 850, 900, 950, 1000, and 1100 MHz.

The Coppermine-128 was used well into 2002. Although always near the bottom of the performance table, it was never completely outclassed, and found a particular niche in low-power applications.

Tualatin Celerons

The next series of Celerons were based on Pentium III Tualatin core, and made with a 0.13 micrometre process. They were nicknamed Tualeron—a portmanteau of the words Tualatin and Celeron. The series began with 1000 and 1100 MHz parts (which were given the extension "A" to their name to differentiate them from the Coppermine-128 of the same speed they replaced) and the line continued with 1200, 1300, and 1400 MHz chips.

Tualerons were identical to their fully-fledged Pentium III sibling, except that Tualerons used a 100 MHz bus rather than a 133 MHz bus (they also had higher latency in the L2 cache, but this never noticably affected performance). They were excellent overclockers, since they had higher multipliers and users could put them on a 133 MHz bus easily. The cache was the same and in the same amount as in the Pentium III; 256KB in both.

These last of the P-6 core Celerons were little-noticed in the marketplace. For some time they were manufactured and sold in parallel with the Pentium 4-based Celerons that would eventually replace them. Most users assumed that the newer parts, with their much higher clockspeeds were significantly faster: they were not, and canny buyers snapped up the last of the P6 Tualatin Celerons, especially in notebook systems where the much lower power consumption translated directly into longer battery life.

Banias-512

These Celerons (sold under the Celeron M brand) are based on the Pentium M, and differs from its parent in that it has half the L2 cache, and does not support the clock-varying SpeedStep technology. They perform reasonably well compared to the Pentium M, but battery life is noticeably shorter on a Celeron M based notebook than it is on a comparable Pentium M notebook.

A notebook with a Celeron M processor is not considered to be part of the Centrino package, regardless of what chipset and Wi-Fi components are used.

Netburst class Celerons

Willamette-128

The next series of Celerons was based on the Pentium 4 "Willamette" core and were, in consequence, a completely different design. These are often known as the Celeron 4. They have 128KB rather than 256KB or 512KB of L2 cache, but are otherwise very similar. Although the P4-based Celerons suffer considerably from their smaller caches, some speed grades have been favored in the enthusiast market, because like the old 300A, they can run well above their rated speeds.

Northwood-128

These Celerons are based on the "Northwood" core, and also have 128KB of cache. They are functionally and featured the same as the Willamette-128 Celeron, and perform largely the same clock-for-clock.

Prescott-256

This is based on the "Prescott" core, and has a larger (than the previous Netburst Celerons) 256KB cache. It also features a 533MHz bus and SSE3, and will have a 3xx model number (compared to 5xx for Pentium 4s and 7xx for Pentium Ms and Pentium 4 Extreme Editions). They will have hardware-level support of Intel's EM64T technology by virtue of it also being built into the Prescott core, but it is unlikely that it will be enabled. For the first time since the introduction of the Celeron range, the brand name will change - to Celeron D.