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Today, we've decided to revisit some of the worst CPUs ever built. To make it on to this list, a CPU needed to be fundamentally broken, as opposed to simply being poorly positioned or slower than expected. The annals of history are already stuffed with mediocre products that didn't quite meet expectations but weren't truly bad.
Note: Plenty of people will bring up the Pentium FDIV bug here, but the reason we didn't include it is simple: Despite being an enormous marketing failure for Intel and a huge expense, the actual bug was tiny. It impacted no one who wasn't already doing scientific computing and the scale and scope of the problem in technical terms was never estimated to be much of anything. The incident is recalled today more for the disastrous way Intel handled it than for any overarching problem in the Pentium micro-architecture.
We also include a few dishonourable mentions. These chips may not be the worst of the worst, but they ran into serious problems or failed to address key market segments. With that, here's our list of the worst CPUs ever made.
- Intel Itanium
- Intel Pentium 4 (Prescott)
- AMD Bulldozer
- Cyrix 6×86
- Cyrix MediaGX
- Texas Instruments TMS9900
Which CPUs make up your list of Worst CPUs Ever Made?
(Score: 2) by toddestan on Thursday April 23 2020, @11:56PM
I had one of those. It was rated a 200+, so supposedly equivalent if not faster than the (somewhat rare) Pentium 200. It actually ran at 150 MHz. For general desktop type stuff, it was fine. It was also okay with the internet as it was back in this CPU's day. However, the FPU was terrible. It could barely play a MP3 file. Well, you could play a MP3, but forget about doing much else with the PC while it was doing it. I also used a K6 233 quite a bit, and the K6 utterly destroyed the 6x86. The K6 could play a MP3 and pretty much still be idling. Ditto for games.
It also wasn't very stable, though for the time it wasn't bad considering I was running Windows 95 and most of the crashes weren't likely the hardware's fault. But nevertheless a big part of the problem was that it was a 150 MHz chip, but unlike the Intel chips which got that with a 60 MHz bus and a 2.5x multiplier, the 6x86 got it with a 75 MHz bus and a 2x multiplier. While this undoubtedly helped it with it's 200+ rating, this hurt its stability quite a bit. I had a Socket 7 motherboard with an Intel VX chipset, which was only rated for 66 MHz (the fastest bus speed Intel ever supported on Socket 7) which meant the chipset was over clocked. The PCI bus ran at half the bus speed, or 37.5 MHz, whereas most any PCI card was expecting 33 MHz max, so all the PCI cards were being overclocked. And the EDO memory was almost certainly being run at a higher speed than it was supposed to. The 6x86 166+ ran at 133 Mhz (66 MHz and 2x, same as the Pentium 133), so I would guess that chip might be more stable.
The 6x86 might fair better in the later Super Socket 7 motherboards which supported up to a 100 MHz bus speed and were backwards compatible with some Socket 7 processors, though those came out after the original 6x86.
Despite its problems, I still don't know if I would call it bad. It was cheap, and it worked well enough for the time.