I voted yes, but for specific reasons.
Was the P4 an engineering failure? Yes and no. Some really good ideas came out of it, and Intel innovated a lot of good stuff in that time (quad pumped FSB, the trace cache, integrating over meg of full-speed 2+ GHz cache memory was a big step in the right direction, hyperthreading (which became much less important with the introduction of multiple CPU's on a single die), etc). Some stuff, like the quad pumped FSB, the Israeli team responsible for the Pentium M just "borrowed" directly for use in their own architecture.
I would say the P4 was ultimately a failure because:
a.) it veered off the roadmap into oblivion after Prescott came out [ie. it failed to meet expectations once it hit the 90nm die shrink)
and
b.) using Intel's MASSIVE engineering resources, they were ultimately overtaken by their Israeli counterpart (the Pentium M team), who, using 1/10th of the resources and building primarily on the Pentium 3 architecture, created what led to the Core/Core2 architecture that Intel is using today.
Intel's design for the Pentium 4 was based on marketing, not engineering. Their idea was to smash the competition into the ground by winning a clockspeed war, IPC (instructions per clock) be damned. AMD took the reverse route, and, upon releasing the Athlon64, gained a large performance lead on Intel in both the desktop and server market.
Right out of the gate, the P4 was a piece of crap; the original P4 with 256K of cache was released at 1.3 and 1.4 GHz, and performed similarly to the 1 GHz Coppermine P3 CPU. It was subsequently tweaked to go up to 1.9 GHz.
The Northwood P4, hower was a brilliant revision, carrying the P4 from 1.8 GHz to 3.2 GHz and beyond. Northwood also took the Pentium 4 from 180nm (0.18um) to 130nm.
Northwood bumped the FSB to 200MHz (800MHz effective), doubled the cache to 512K, and pulled away from AMD's Athlon through sheer clockspeed (Intel's original intention). Even AMD's model numbers were defeated by the Northwood; a 3 GHz Pentium 4 outperformed an AMD Athlon 3200+ at 2.2 GHz.
But that's where nature reared its ugly head, and power leakage (among other factors) made the 90nm die shrink (called Prescott) run ridiculously hot, and barely outperformed the Northwood core. And they needed to add length of the pipeline on Prescott, I believe going from 20 to 30. The end result was that per MHz, Northwood was marginally faster, even though Prescott had double the L2 cache. The Prescott dual cores were such a knee-jerk reaction to AMD that they barely deserve mention. They simply ran too hot, and consumed an inordinate amount of power. Intel designed the ill-fated BTX platform around the fact that Prescott CPU's were producing so much head, that they needed a better way to exhaust it out of the system. We have AMD's sucessful Athlon64 to thank for not letting BTX gain much foothold, except in the micro-case market.
If Intel didn't have the massive lead in manufacturing capacity, Prescott could have almost put them out of business, but Intel took the step to 65nm so much earlier than AMD (almost 2 years) that they were able to get away with putting so much cache onto their CPU's to stay somewhat competitive, versus the much larger 90nm chips AMD has been producing until just recently.
Prescott was supposed to take the P4 from 3+ GHz to 5+ GHz, and Intel was planning on hitting 8-10 GHz by 2008/2009. Needless to say, that didn't happen... The Pentium 4 was a 10-year architecture design that lasted about 5 years before it became unviable to proceed.
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So was the pentium 4 a failure? From an engineering perspective, ultimately yes.
But if you own a Pentium 4 Northwood CPU, it's still a decent CPU today for most applications (hardcore gaming aside). It's better than an AMD Athlon XP, or anything that came before the P4.
But the Core/Core2 (in single and multiple CPU configurations) as well as the Athlon64 are smarter, cooler-running, higher-IPC, better designed CPUs.