Hardware Reference
In-Depth Information
Note
Intel's change from using numbers (386/486) to names (Pentium/Pentium Pro) for its pro-
cessors was based on the fact that it could not secure a registered trademark on a number
andthereforecouldnotpreventitscompetitorsfromusingthosesamenumbersonclonechip
designs.
The first processor in the P6 (686) family, called the Pentium Pro processor, was intro-
duced in 1995. With 5.5 million transistors, it was the first to be packaged with a second
die containing high-speed L2 memory cache to accelerate performance.
Intel revised the original P6 (686/Pentium Pro) and introduced the Pentium II processor
in May 1997. Pentium II processors had 7.5 million transistors packed into a cartridge
rather than a conventional chip, allowing the L2 cache chips to be attached directly on the
module. The Pentium II family was augmented in April 1998, with both the low-cost Cel-
eron processor for basic PCs and the high-end Pentium II Xeon processor for servers and
workstations. Intel followed with the Pentium III in 1999, essentially a Pentium II with
Streaming SIMD Extensions (SSE) added.
Around the time the Pentium was establishing its dominance, AMD acquired NexGen,
which had been working on its Nx686 processor. AMD incorporated that design along
with a Pentium interface into what would be called the AMD K6. The K6 was both hard-
wareandsoftwarecompatiblewiththePentium,meaningitpluggedintothesameSocket
7 and could run the same programs. As Intel dropped its Pentium in favor of the more ex-
pensive Pentium II and III, AMD continued making faster versions of the K6 and made
huge inroads in the low-end PC market.
In1998,Intel became the first to integrate L2 cache directly onthe processor die (running
at the full speed of the processor core), dramatically increasing performance. This was
first done on the second-generation Celeron processor (based on the Pentium II core), as
well as the Pentium IIPE (performance-enhanced) chip used only in laptop systems. The
first high-end desktop PC chip with on-die full-core speed L2 cache was the second-gen-
eration (Coppermine core) Pentium III introduced in late 1999. After this, all major pro-
cessor manufacturers began integrating L2 (and even L3) cache on the processor die, a
trend that continues today.
AMD introduced the Athlon in 1999 to compete with Intel head to head in the high-end
desktop PC market. The Athlon became successful, and it seemed for the first time that
Intel had some real competition in the higher-end systems. In hindsight, the success of
the Athlon might be easy to see, but at the time it was introduced, its success was any-
thing but assured. Unlike the previous K6 chips, which were both hardware and software
