I... I had one.
There I was at the Old Pigsty, trucking along nicely since 1998 with my Pentium 200MMX which, despite the memes, was a good CPU right up until the year 2000. Could play Unreal Tournament, Tiberian Sun, all the Quakes, System Shock 2, and Baldur's Gate no problem. Then, we got an upgrade! We trucked out to PC World ('member PC World?) in mid 2001 and got ourselves a lovely new prebuilt from Packard Bell in a rather swish blue case. In fact, it looked
just like this. GeForce 2 GPU, 256 MB RAM, 40 GB hard drive... and a Pentium 4 at 1.5 GHZ.
So, bragged about it the next day to school friends. One of them told me he had an Athlon 900. This was a CPU that was a year older and went up against the Pentium III at the time, but he reckoned it was faster. But me, being the brainless proto-consoomer I was, say, "is not! Yours is only 900 MHz while mine's 1,500 MHz! S'there!" So we agreed to go away and benchmark it.
It was ogre. The P4 was humiliated.
Turns out that the Pentium 4 was really, really fast at number crunching and performing loads of mathematical and logical operations so long as it didn't have to rely upon other things or carry out too many if/then/else type operations. This is because it had a yuge pipeline and this was how they got it to for the time dizzying high speeds. But if it predicted the wrong branch, it had to stop, flush the pipeline, and start again.
Despite this, when I went off to university I acquired a Pentium 4 based laptop (which oddly enough had a desktop class P4 at 2.8 GHz) and so never learned. Its battery life was shit and there was a torrent of hot air permanently emerging from the side vents.
But yeah, the Pentium 4 was an architecture that started out poorly, became adequate two years too late with the Northwood core, and then took a hard turn into awfulness again with Prescott and Cedar Mill which had the added fun bonus of cooking themselves. Yet despite this, there was worse. The Pentium 4 based Celerons, for instance. In 2010 I started my training contract and the PCs at the firm were all old XP based boxes running Celeron D processors. Despite the name, these were single core and gimped versions of Prescott Pentium 4s. They are possibly the worst CPU I have ever, ever, used. Literally having Word, Excel, our case management software, and Firefox open all at once would bog them to rage-inducing levels, and having more than three Firefox tabs open at once would make them lock up totally for about two or three minutes.
EDIT: If you want to experience the agony of the Celeron D,
you can buy TWO for literally less than the cost of a pint.