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No there’s no Pentium 5!
All of the currently available and upcoming Intel performance desktop processors use Pentium 4 technology. The ‘Tejas’ project which was intended to produce the ‘Pentium 5’ was discontinued and abandoned earlier in 2004, and just lately Intel has also abandoned plans to produce a 4 GHz Pentium 4 processor as well. Intel is in a ‘bit of a pickle’!
The ‘Tejas’ project was not the only one discontinued by Intel, and the next couple of years might prove to be a slow period for the processor ‘Giant’ until new projects are brought to fruition.
The processor improvements keep rolling out. Intel just decided to abandon the Px designations. P3 and then P4 had a pretty poor performance showing compared to AMD products at the time. When it came time to release the next generation processor Intel went with the new designation "Core 2" to indicate it was a radical departure from the limited P3/P4 architecture. P4's can still be had, but the Core 2, which is effectively the P5, is a much superior design.
Now the Nehalem (aka I7, aka Intel 7) is taking the next big jump in processor evolution incorporating better memory management capability as well as other features.
The attempt to push processor speeds to 4 gigahertz hit a brick wall in material physics so multi core architectures have been used to increase performance.