The Top 5 Worst CPUs of All Time

Author:Daniel Dobrowolski

Editor:Kyle Bennett

Date: Thursday , August 17, 2017

We reach back over 20 years to think about what are worst CPUs we have ever had to deal with. Whether it be technical issues or for reasons of simply disappointing the market, these CPUs sucked in some way. Some CPUs you will remember, so you won't, and some you will wish that you did not remember.

The Top 5 Worst CPUs of All Time

Inspired by a recent HardForum post touching on my thoughts on Intel's Core i7-7740X CPU, I thought we would put together another "Top 5" countdown, this time covering the "Worst CPUs of All Time." This is going to be another tough one because a lot of players have come and gone over the years and both the remaining challengers left standing have produced some turds in their day. Processors will be judged on several criteria. Among these criteria will be relevance, market lifespan, performance, overclockability, timing, innovation, and anything else I can think of at the time. A previously, this is very much an editorial based simply on my thoughts and experiences over the past couple of decades working with computer hardware.

5. - AMD K5 (1996)

AMD's K5 can be summarized in a few cheesy but accurate phrases: Too little, too late, and woefully inadequate. Like Cyrix, AMD took ideas from the Pentium Pro and integrated those into K5 CPU's design. Unfortunately, the CPU performed more like a standard Pentium but worse. Floating point performance was weaker than Intel's at a time when games were starting to leverage the FPU heavily. This K5 is also notable for introducing the "Performance Rating" or "PR" numbering system. It was AMD's claim that a 116MHz K5 actually performed about the same as a Pentium clocked at 166MHz. AMD decided to market it as the "K5 PR166," even though it was actually not a 166MHz processor. This was wishful thinking on AMD's part and this CPU was probably AMD's biggest failure to date. Of course that is debateable too.

4. - Cyrix MII (1996)

This Cyrix MII CPU was another one that was late to the party. It was a follow up to the incredibly successful, and generally very good Cyrix 6x86. Unfortunately, the chip couldn't scale well with clock speeds, ran as hot as its predecessors, and fell well short of Intel's offerings due to poor FPU performance. This Cyrix MII wasn't bad in the technical sense as much as it was a victim of being late to the market. Had this chip come out during the early days of Cryix' 6x86 it would have been far better received.

3. - Intel Itanium (2001)

This original Intel Itanium was an easy choice for the list. The original "Merced" Itaniums attempted to compete against IBM's POWER architecture and Sun Microsystem's SPARC CPUs. Neither competing companies had anything to worry about. This CPU introduced Intel's "IA-64" architecture which failed to get any real market traction and would be supplanted by AMD's x86-64, which even Intel itself would adopt in its own form. Merced Itaniums only made it into a few thousand systems during it's very short life span as Intel had to follow up with a replacement very quickly. Itanium II would debut a mere year later as a result of this fiasco. Somehow the Itanium branding has stuck around to this day, though the Itanium 9700 series will be the last before dying off completely.

2. - AMD Bulldozer (2011)

AMD's Bulldozer CPU was another easy choice to make the all time worst list. The Bulldozer CPU architecture is often referenced as AMD's "Pentium IV" or "AMD's Netburst." These statements are far more accurate on a technical level than people usually realize. It took the core tenets of what was wrong with the Netburst architecture and failed at them more spectacularly. AMD's Phenom CPUs weren't terribly successful and people hoped that Bulldozer would return AMD to the forefront of performance and the glory days of K7 and K8. Sadly, that wasn't to be the case. AMD took a page out of Intel's book and created an architecture that would scale well with clock speeds at the expense of IPC performance. AMD had hoped it would see widespread adoption in the server market where it wasn't nearly as bad. Unfortunately, high power consumption, lots of heat and again, low IPC made this CPU a bad option. Sure it performs well when performing very specific heavily multithreaded workloads, but it wasn't exactly a real competitor to the Xeon outside of very limited circumstances either. The only thing that allowed any of these to sell was bargain basement pricing and backwards compatibility with AM3 motherboards. If AMD had priced them any cheaper and they could have sold them in vending machines. Bulldozer marked AMD's surrender of the server market that Intel now owns what now some estimated to be above 99%. AMD is looking again punch into the server market with the recent EPYC processor launch.

1. - Intel Pentium 60/66MHz (1993)

The Intel Pentium 60/66MHz CPU had to be number one, at least in my mind. This CPU in it's original P5 (socket 4) form was ahead of its time in many ways but soon became overshadowed by the Pentium Pro. The Intel Pentium 60/66MHz CPU had truly incredible IPC performance in its day as it competed with i468 and AMD 486 CPUs with almost double the clock speed and did so very well. Unfortunately, the original 60 and 66MHz Pentium failed in one important area: It couldn't do math reliably. The bug became known as the "Pentium FDIV bug." This CPU created havoc like none other as people discovered months and even years of math done by computer had to be rechecked. The extent of how often it would throw out bad math isn't truly known as it went unnoticed for around a year. Until that point it was generally believed that a computer's logic, where applicable was never wrong and Intel shocked everyone by proving CPUs could indeed be wrong. Strangely, Intel launched it's "Intel Inside" campaign which is one of the most successful marketing campaigns of all time in the wake of this disaster.

Honorable Mention

Editor's Note: Of course the original Intel Pentium III 1.13GHz fiasco remains near and dear to my heart.

Closing Thoughts

There are plenty of other potentially awful CPU's I could have included here. The Pentium IV is surprisingly absent from this list. While the Athlon's of the day were usually faster, the Pentium IV was still often priced competitively in some price brackets and several of them were solid overclockers. The Pentium 2.4C's that overclocked to 3.0GHz were one such examples. Those were solid enthusiast offerings even if they weren't the fastest on the block at the time. It is for those reasons why I couldn't include it despite how awful the series was remembered. The CPU market is once again exciting with AMD's Ryzen and Threadripper products making it to market, and luckily I don't see any "bad" CPUs being added to a list like this anytime soon. Though I do have a particular hatred of the Core i7 7740X, so who knows? I may have a very different countdown a year or so from now.