Intel: A Bug and a Pro
45 comments
·March 24, 2025jmclnx
About the F00F bug, and a nice read.
Edit:
Seems IBM stopping shipment of these buggy PCs forced Intel to fix the problem. I cannot imaging today's IBM doing something like this.
rbanffy
> I cannot imaging today's IBM doing something like this.
Today's IBM doesn't ship Intel servers, or Intel anything. They sold that part of their business to Lenovo.
piokoch
People forget that a company known as IBM went bankrupt, was sold and reborn as a consulting enterprise like Accenture or McKinsey. The only thing that remained from the olden days are servers, in particularly z-series, which are modern days equivalents of mainframe solutions (and they are pretty awesome).
perching_aix
Sounds like you might be personally familiar with (their?) mainframes.
Could you explain what's awesome about them, and what even are mainframes? Whenever I tried looking into this, I walked away with "just servers networked together".
rbanffy
They almost went bankrupt. Starting with Lou Gerstner, IBM cut out the least profitable parts (commodity PCs, then, later, commodity servers), and focused on services (which also acts as a sales enabler) and high-margin hardware and software.
wglb
However I was quite concerned at the time when they said, quite incorrectly that there was no risk to their users from this bug.
charcircuit
What is the risk? It seems very small to me.
wglb
The risk is that some divisions will be fully off. If it is a chain of calculations, e.g. some stress analysis, or a spreadsheet involving a chain of calculations for a financial report, it could be bad.
bendercorn
Should have mentioned that intel marketing and PR launched the User Test Program to make sure advanced users got early PPro systems to make sure there were no lurking fdivs. Nicely was the first recipient. So was John Williams the composer.
rbanffy
John Williams from Star Wars or John Williams from Sky?
defrost
rim shot: https://youtu.be/QgbgUrp1a70?t=67
FWiW I bought (one of) Kevin Peek's guitar amps in 1982 in Kalamunda (W.Australia) .. it was just an ad in the classifieds, got out there and it was a damn near world class music studio in a one room music cabin in the bush.
bendercorn
[dead]
ankitg12
Related discussion sometime back - https://news.ycombinator.com/item?id=42535071
jeffs4271
I am just shocked to see a MIPs R8000 reference in 2025. It was relatively obscure CPU targeted at HPC and weaker at integer workloads. I worked on a lot of cool stuff, but that project was probably the most fun.
wuming2
Care to expand?
Also I often wonder what the aggregate statistics of `top` load average and standard deviation looks like over billions of consumer devices over time.
adrian_b
The Intel marketing is responsible for a large number of despicable decisions during the years, but I consider that by far the most despicable thing done by them happened when they have segmented their CPU products into Pentium and Pentium Pro.
Later, they have dropped the "Pro" naming scheme and the successors of "Pentium Pro" have been branded as "Xeon", until today.
IBM had been wise and they had incorporated memory error detection as a standard feature of every IBM PC, so that has also been true for all IBM PC clones.
By the early nineties, when the memories packaged in dual-in-line packages have been replaced by memory modules, you could buy complete memory modules with error detection, but there were also slightly cheaper memory modules without error detection, so a computer owner could choose either of them. I am not a gambler, so I have always used only modules with error detection.
However that has changed in 1994, when Intel has decided to split their CPUs into Pentium for "consumers" and Pentium Pro for "professional users" who were willing to spend much more for a workstation or server computer.
This is when Intel has decided that in order to stimulate their customers to buy overpriced "Pro" CPUs, memory error detection must be removed from their "consumer" CPUs.
While in 1993 the first generation of computers with Pentium still had memory error detection, for the second generation in 1994 (with the Triton chipsets), memory error detection was removed, in preparation for the launch of Pentium Pro next year.
We will never know the value of the financial losses that have been inflicted worldwide upon naive computer users by this Intel decision.
Fortunately for Intel and unfortunately for us, software bugs have always been so frequent that all computer users have been conditioned to assume automatically that whenever the computer crashes or data corruption is discovered, the cause must have been some software bug and it must be difficult or impossible to determine the exact culprit.
Despite this common assumption, many of these incidents may be caused by hardware memory errors and besides the noticed incidents there may be many other cases of data corruption that have never been discovered.
The claim of Intel that this removal of memory error detection has been done for the benefit of the customers, to reduce the price of the computers, is of course false. After it became impossible to have memory error detection in "consumer" PCs, there was no price reduction in motherboards or memory modules, the prices have remained the same and their vendors had increased profits, so they have supported enthusiastically the initiative of Intel.
Interestingly Linux uses "Coe's ratio" (4195835/3145727) dating from 1994 to check for the FDIV bug.
Coe's ratio: https://people.cs.vt.edu/~naren/Courses/CS3414/assignments/p... (3rd page)
Linux code: https://github.com/torvalds/linux/blob/b0cb56cbbdb4754918c28...