Tejas was a code name forIntel'smicroprocessor, which was to be a successor to the latestPentium 4 with thePrescott core and was sometimes referred to asPentium V.[1]Jayhawk was a code name for itsXeon counterpart. The cancellation of the processors in May 2004 underscored Intel's historical transition of its focus on single-core processors tomulti-core processors.
In early 2003, Intel showed Tejas and a plan to release it sometime in 2004 with possible delays into 2005. Its development however, was cancelled on May 7, 2004.[2] Analysts attribute these issues to heat and power consumption problems due to Intel's goal of reaching ever higher clock speeds, at the detriment of work done per clock (and therefore performance per clock). This was already the case with Prescott and its mediocre performance increase overNorthwood despite higher clock speeds, not to mention heavy competition fromAdvanced Micro Devices with theirAthlon 64. Prescott was supposed to attain >5 GHz speeds with ease, yet this was not possible due to physical limitations such as heat generated and power consumed at ambient temperatures (the "power wall"). Tejas went even further ahead with this paradigm, with Intel targeting 10 GHzclock speeds by 2011 trying to fulfill the prediction made byAndrew Grove in his keynote speech at the 1996COMDEX/Fall.[3] Soon enough it was clear this represented a dead end.
This cancellation reflected Intel's intention to focus on dual-core chips for theItanium platform. With respect todesktop processors, Intel's development efforts shifted to thePentium M microarchitecture (itself a derivative of theP6 microarchitecture last used in thePentium III) used in theCentrino notebook platform, which offered greatly improved performance per watt compared to Prescott and otherNetBurst designs. The result of modernizing the P6 microarchitecture was theCore processor line, and later theCore 2 line, offering Intel's first native dual core products for desktops andlaptops while regaining the performance crown[4] back from AMD.
This defined the end for the NetBurst architecture, with Core setting the foundation and path for power efficient architectures that followed along theTick–tock model. Although NetBurst was a dead end for the company, its concepts were later reused and repurposed[5] inSandy Bridge.
To bridge the gap left by Tejas' cancellation in the x86 market, Intel did one last revision to NetBurst, codenamedCedar Mill (single core) and Presler (dual core).
Tejas and Jayhawk were to make several improvements on the Pentium 4'sNetBurst microarchitecture. Tejas was originally to be built on a90 nm process, later moving to a65 nm process. The 90 nm version of the processor was reported to have 1 MB L2cache, while the 65 nm chip would increase the cache to 2 MB. There was also to be adual core version of Tejas calledCedarmill (orCedar Mill depending on the source). ThisCedarmill should not be confused with the 65 nm Cedar Mill-based Pentium 4, which appears to be what the codename was recycled for.
Thetrace cache capacity would likely have been increased, and the number of pipeline stages was increased to between 40 and 50 stages.[6] There would have been an improved version ofHyper-Threading, as well as a new version ofSSE, which was later backported to the Intel Core 2 series and namedSSSE3. Tejas was slated to operate at frequencies of 7GHz[1] or higher. However, it's likely that Tejas wouldn't have had linear performance scaling, as it would on average have executed fewer instructions per clock cycle due to more pipeline bubbles from branch mispredicts and data cache misses. Also, it would have run hotter as well with aTDP much higher than the Prescott core of Pentium 4. The CPU was cancelled late in its development after it had reached itstapeout phase.[6]
Initial claims reported early samples of single core 90 nm Tejas running at 2.8 GHz and rated for 150 W TDP on theLGA 775 socket,[7] a notable increase over single core 90 nm Prescott (Pentium 4 521, 2.8 GHz, 84 W TDP)[8] and higher than 90 nm dual core Smithfield (Pentium D 820, 2.8 GHz, 95 W TDP).[9] In contrast, 65 nm dual core Core 2 Duo processors had a maximum of 65 W TDP (E6850, 3.00 GHz)[10] while being much more efficient with markedly higher performance per clock.
However, the existence ofengineering samples have been challenged and no source indicates that tape-out of Tejas ever existed - the sample shown in theAnandTech article[7] being a Prescott B0 ES.[11] Most probably only thermal samples of Tejas were produced.
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