With such a competitive landscape, both AMD and Intel started launching newer grades of their processors, with increasing processor frequencies, all within a short time frame between 1999 and 2000. Not surprisingly, the significant 1GHz mark was soon breached and AMD's Athlon claimed that honor. It was obvious. AMD's star was in ascendancy and its next revision of the Athlon, the Thunderbird would improve on the original Athlon by having a faster and better cache design. These were heady days for the company and with the Pentium III falling behind in benchmarks, AMD was quickly gaining market share at the expense of Intel. To match its aspirations, the company started ramping its manufacturing capacity with new fabrication plants, though they remain far behind Intel.
This clock speed race between the two major microprocessor firms raged on as we entered the 21st century. Intel came back with a new micro-architecture, NetBurst that could be scaled up to extremely high clock speeds, due to a 20-stage deep instruction pipeline first used on the original Pentium 4. This meant that Intel was soon launching CPUs with clock speeds that were higher than anything from AMD, though they were not necessarily faster in benchmark performance. Less informed consumers who have always relied on processor clock speeds as a rough gauge of performance were hence inclined to favor Intel's Pentium 4 products.
This prompted AMD to introduce its PR (performance rating) system of marketing its processors, which pegged the processors relative to a baseline system. This was seen with the third Athlon revision, the Palomino, also known as the Athlon XP. AMD also sought to highlight the 'myth' of the clock speed with advertising efforts and concealed the true clock speeds of its processors (except within the BIOS) in favor of the PR system, as they were often inferior to Intel's higher clocked Pentium 4.
Of course, there came to be a time when Intel's Pentium 4 started encroaching onto the Athlon's performance lead. The introduction of the new Intel 845 chipset that used cheaper SDRAM instead of Intel's ill-conceived venture into RAMBUS in 2001 helped bring Pentium 4 to the mainstream consumer. Meanwhile, Intel continued to scale up its micro-architecture with newer cores that soon ventured into the 2GHz territory and beyond. Intel was aided by its transition to a 130nm process, allowing the company to increase transistor count and clock speeds. These newer Northwood cores introduced in 2002 also came with Intel's HyperThreading technology, which was a form of pseudo-multiprocessing that allowed multiple threads to be executed by simulating the presence of two logical processors such that the supported operating system can schedule two threads or processes.
Meanwhile, AMD's own switch to 130nm did not yield the higher clock speeds needed to overcome Intel's new Pentium 4. Other improvements to the design like a larger cache and higher FSB also failed to raise the performance sufficiently. It was time for AMD to come up with a new micro-architecture.
This new K8 micro-architecture would be found first in a server oriented processor, the Opteron. Representing AMD's hopes of making inroads into Intel's server class Xeon processors, the Opteron was launched in April 2003 and was unique in being able to run legacy 32-bit applications without any performance penalty, despite the fact that it was actually a 64-bit processor. Enabling this was AMD's x86-64 instruction set (AMD64), which would eventually be duplicated by Intel (Intel 64) a year later. However, this meant that when the Opteron debuted, Intel had no quick response to this additional feature. As a result, AMD started posting impressive growth figures for its server processors and some major vendors like Sun and HP would eventually offer Opteron powered workstations and servers.
AMD would follow up the server version with the desktop version, dubbed the Athlon 64, to leave consumers no doubts about its 64-bit pedigree. With performance that restored competitiveness with the faster Pentium 4 processors in the market, AMD had a moderately successful product on its hands but it could only produce very limited quantities. Core revisions in the following year led to various improvements like a faster HyperTransport bus and a dual channel memory controller but before this, Intel already had its newest 90nm Pentium 4 revision, Prescott (with an even deeper pipeline), available for a couple of months.
By then, the clock speeds of the faster Prescott Pentium 4 were already over the 3GHz mark. AMD's powerful FX-55 processor was not too shabby either in the clock department at 2.6GHz, especially when it was on a 130nm process technology. While AMD was to also migrate over to a 90nm process for its next core revision, the writing was on the wall for Intel. The Prescotts were running warmer than consumers would have liked, along with a corresponding increase in power consumption. Intel's earlier predictions of hitting 5GHz and higher seemed like fantasy as even 4GHz Prescotts looked difficult to achieve. The era of the frenetic clock race was coming to an end.