Some time ago, Linus Torvalds made a throwaway comment that sent ripples through the Linux world. Was it perhaps time to abandon support for the now-ancient Intel 486? Developers had already abandoned the 386 in 2012, and Torvalds openly mused if the time was right to make further cuts for the benefit of modernity.

It would take three long years, but that eventuality finally came to pass. As of version 6.15, the Linux kernel will no longer support chips running the 80486 architecture, along with a gaggle of early “586” chips as well. It’s all down to some housekeeping and precise technical changes that will make the new code inoperable with the machines of the past.

Why Won’t It Work Anymore?

The big change is coming about thanks to a patch submitted by Ingo Molnar, a long time developer on the Linux kernel. The patch slashes support for older pre-Pentium CPUs, including the Intel 486 and a wide swathe of third-party chips that fell in between the 486 and Pentium generations when it came to low-level feature support.

Going forward, Molnar’s patch reconfigures the kernel to require CPUs have hardware support for the Time Stamp Counter (RDTSC) and CMPXCHG8B instructions. These became part of x86 when Intel introduced the very first Pentium processors to the market in the early 1990s. The Time Stamp Counter is relatively easy to understand—a simple 64-bit register that stores the number of cycles executed by the CPU since last reset. As for CMPXCHG8B, it’s used for comparing and exchanging eight bytes of data at a time. Earlier Intel CPUs got by with only the single-byte CMPXCHG instruction. The Linux kernel used to feature a piece of code to emulate CMPXCHG8B in order to ease interoperability with older chips that lacked the feature in hardware.

The changes remove around 15,000 lines of code. Deletions include code to emulate the CMPXCHG8B instruction for older processors that lacked the instruction, various emulated math routines, along with configuration code that configured the kernel properly for older lower-feature CPUs.

Basically, if you try to run Linux kernel 6.15 on a 486 going forward, it’s just not going to work. The kernel will make calls to instructions that the chip has never heard of, and everything will fall over. The same will be true for machines running various non-Pentium “586” chips, like the AMD 5×86 and Cyrix 5×86, as well as the AMD Elan. It’s likely even some later chips, like the Cyrix 6×86, might not work, given their questionable or non-existent support of the CMPXCHG8B instruction.

Why Now?

Molnar’s reasoning for the move was straightforward, as explained in the patch notes:

In the x86 architecture we have various complicated hardware emulation
facilities on x86-32 to support ancient 32-bit CPUs that very very few
people are using with modern kernels. This compatibility glue is sometimes
even causing problems that people spend time to resolve, which time could
be spent on other things.

Indeed, it follows on from earlier comments by Torvalds, who had noted how development was being held back by support for the ancient members of Intel’s x86 architecture. In particular, the Linux creator questioned whether modern kernels were even widely compatible with older 486 CPUs, given that various low-level features of the kernel had already begun to implement the use of instructions like RDTSC that weren’t present on pre-Pentium processors. “Our non-Pentium support is ACTIVELY BUGGY AND BROKEN right now,” Torvalds exclaimed in 2022. “This is not some theoretical issue, but very much a ‘look, ma, this has never been tested, and cannot actually work’ issue, that nobody has ever noticed because nobody really cares.”

Basically, the user base for modern kernels on old 486 and early “586” hardware was so small that Torvalds no longer believed anyone was even checking whether up-to-date Linux even worked on those platforms anymore. Thus, any further development effort to quash bugs and keep these platforms supported was unjustified.

It’s worth acknowledging that Intel made its last shipments of i486 chips on September 28, 2007. That’s perhaps more recent than you might think for a chip that was launched in 1989. However, these chips weren’t for mainstream use. Beyond the early 1990s, the 486 was dead for desktop users, with an IBM spokesperson calling the 486 an “ancient chip” and a “dinosaur” in 1996. Intel’s production continued on beyond that point almost solely for the benefit of military, medical, industrial and other embedded users.

If there was a large and vocal community calling for ongoing support for these older processors, the kernel development team might have seen things differently. However, in the month or so that the kernel patch has been public, no such furore has erupted. Indeed, there’s nothing stopping these older machines still running Linux—they just won’t be able to run the most up-to-date kernels. That’s not such a big deal.

While there are usually security implications around running outdated operating systems, the simple fact is that few to no important 486 systems should really be connected to the Internet anyway. They lack the performance to even load things like modern websites, and have little spare overhead to run antiviral software or firewalls on top of whatever software is required for their main duties. Operators of such machines won’t be missing much by being stuck on earlier revisions of the kernel.

Ultimately, it’s good to see Linux developers continuing to prune the chaff and improve the kernel for the future. It’s perhaps sad to say goodbye to the 486 and the gaggle of weird almost-Pentiums from other manufacturers, but if we’re honest, few to none were running the most recent Linux kernel anyway. Onwards and upwards!

People have been talking about switching from Windows to Linux since the 1990s, but in the world of open-source operating systems, there is much more variety than just the hundreds of flavors of Linux-based operating systems today. Take FreeBSD, for example. In a recent [GNULectures] video, we get to see a user’s attempt to switch from desktop Linux to desktop FreeBSD.

The interesting thing here is that both are similar and yet very different, mainly owing to their very different histories, with FreeBSD being a direct derivative of the original UNIX and its BSD derivative. One of the most significant differences is probably that Linux is just a kernel, with (usually) the GNU/Hurd userland glued on top of it to create GNU/Linux. GNU and BSD userland are similar, and yet different, with varying levels of POSIX support. This effectively means that FreeBSD is a singular OS with rather nice documentation (the FreeBSD handbook).

The basic summary here is that FreeBSD is rather impressive and easy to set up for a desktop, especially if you use a customized version like GhostBSD. Despite Libreboot, laptop power management, OSB NVENC, printer, and WiFi issues, it was noted that none of these are uncommon with GNU/Linux either. Having a single package manager (pkg) for all of FreeBSD (and derivatives) simplifies things a lot. The bhyve hypervisor makes running VMs a snap. A robust ZFS filesystem is also a big plus.

What counts against desktop FreeBSD in the end is a less refined experience in some areas, despite FreeBSD being able to run Linux applications courtesy of binary compatibility. With some developer love and care, FreeBSD might make for a nice desktop alternative to GNU/Linux before long, one that could be tempting even for the die-hard Windows holdouts among us.

Old hardware tends to get less support as the years go by, from both manufacturers and the open-source community alike. And yet, every now and then, we hear about fresh attention for an ancient device. Consider the ancient SoundBlaster sound card that first hit the market 31 years ago. [Mark] noticed that a recent update squashed a new bug on an old piece of gear.

Jump over to the Linux kernel archive, and you’ll find a pull request for v6.16-rc3 from [Takashi Iwai]. The update featured fixes for a number of sound devices, but one stands out amongst the rest. It’s the SoundBlaster AWE32 ISA sound card, with [Iwai] noting “we still got a bug report after 25 years.” The bug in question appears to have been reported in 2023 by a user running Fedora 39 on a 120 MHz Pentium-based machine.

The fixes themselves are not particularly interesting. They merely concern minutiae about the DMA modes used with the old hardware. The new updates ensure that DMA modes cannot be changed while the AWE32 is playing a PCM audio stream, and that DMA setups are disabled when changing modes. This helps avoid system lockups and/or ugly noises emanating from the output of the soundcard.

It’s incredibly unlikely this update will affect you, unless you’re one of a handful of users still using an ISA soundcard in 2025. Still, if you are — and good on you — you’ll be pleased someone still cares about your user experience. Meanwhile, if you’re aware of any other obscure old-school driver updates going on out there, don’t hesitate to let us know on the tips line. Want to relive your ISA card’s glory days? Plug it into USB.

Image credit: Gona.eu, CC BY-SA 3.0

[Thanks to Meek Mark for the tip!]

To paraphrase an old joke: How do you know if someone is a Rust developer? Don’t worry, they’ll tell you. There is a move to put Rust everywhere, even in the Linux kernel. Not going fast enough for you? Then check out Asterinas — an effort to create a Linux-compatible kernel totally in Rust.

The goal is to improve memory safety and, to that end, the project describes what they call a “framekernel.” Historically kernels have been either monolithic, all in one piece, or employ a microkernel architecture where only bits and pieces load.

A framekernel is similar to a microkernel, but some services are not allowed to use “unsafe” Rust. This minimizes the amount of code that — in theory — could crash memory safety. If you want to know more, there is impressive documentation. You can find the code on GitHub.

Will it work? It is certainly possible. Is it worth it? Time will tell. Our experience is that no matter how many safeguards you put on code, there’s no cure-all that prevents bad programming. Of course, to take the contrary argument, seat belts don’t stop all traffic fatalities, but you could just choose not to have accidents. So we do have seat belts. If Rust can prevent some mistakes or malicious intent, maybe it’s worth it even if it isn’t perfect.

Want to understand Rust? Got ten minutes?

Theoretically when you write a GUI-based application for Linux there are standards to follow, with these all neatly documented over at the Freedesktop website. However, in reality, Freedesktop is more of a loose collection of specifications, some of which are third-party specifications that have somehow become the de facto standard. One example of this is the StatusNotifierItem spec that provides a way for applications to create and manage a ‘system tray’ icon.

This feature is incredibly useful for providing a consistent way to users for quickly accessing functionality and to see application status. Unfortunately, as [Brodie Robertson] notes in a recent video, not everyone agrees with this notion. Despite that Windows since 95 as well as MacOS/OS X and others provide similar functionality, Gnome and other Linux desktop environments oppose such system tray icons (despite a popular extension), with an inevitable discussion on Reddit as a result.

Although the StatusNotifierItem specification is listed on the Freedesktop website, it’s under ‘Draft specifications’ along with another, apparently internal-but-unfinished System tray proposal. Meanwhile DEs like KDE have integrated first-party support (KStatusNotifierItem) for the specification. There’s currently an active Freedesktop Gitlab discussion on the topic, whether StatusNotifierItem should even be in the list, or become an approved specification.

With the specification mired in bureaucracy and multiple camps pushing their own idea of what ‘the Linux desktop’ should look like, it feels like a real shame that the Linux Standard Base effort died a decade ago. Users and developers just want their desktop environment to come with zero surprises, after all.