Intel 486

3 Articles

Intel 486 Support Likely To Be Removed In Linux 7.1

April 7, 2026 by 43 Comments

Although everyone’s favorite Linux overlord [Linus Torvalds] has been musing on dropping Intel 486 support for a while now, it would seem that this time now has finally come. In a Linux patch submitted by [Ingo Molnar] the first concrete step is taken by removing support for i486 in the build system. With this patch now accepted into the ‘tip’ branch, this means that no i486-compatible image can be built any more as it works its way into the release branches, starting with kernel 7.1.

No mainstream Linux distribution currently supports the 486 CPU, so the impact should be minimal, and there has been plenty of warning. We covered the topic back in 2022 when [Linus] first floated the idea, as well as in 2025 when more mutterings from the side of [Linus] were heard, but no exact date was offered until now.

It remains to be seen whether 2026 is really the year when Linux says farewell to the Intel 486 after doing so for the Intel 386 back in 2012. We cannot really imagine that there’s a lot of interest in running modern Linux kernels on CPUs that are probably older than the average Hackaday reader, but we could be mistaken.

Meanwhile, we got people modding Windows XP to be able to run on the Intel 486, opening the prospect that modern Windows might make it onto these systems instead of Linux in the ultimate twist of irony.

An 80386 Upgrade Deal And Intel 486 Competitor: The Cyrix Cx486DLC

September 15, 2024 by 12 Comments

The x86 CPU landscape of the 1980s and 1990s was competitive in a way that probably seems rather alien to anyone used to the duopoly that exists today between AMD and Intel. At one point in time, Cyrix was a major player, who mostly sought to provide a good deal that would undercut Intel. One such attempt was the Cx486DLC and the related Tx486DLC by Texas Instruments. These are interesting because they fit in a standard 386DX mainboard, are faster than a 386 CPU and add i486 instructions. Check your mainboard though, as these parts require a mainboard that supports them.

This is something that [Bits und Bolts] over at YouTube discovered as well when poking at a TX486DLC (TI486DLC) CPU. The Ti version of the Cyrix Cx486DLC CPU increases the 1 kB L1 cache to 8 kB but is otherwise essentially the same. He found the CPU and the mainboard in the trash and decided to adopt it. After removing the very dead battery from the Jamicon KMC-40A Baby AT mainboard, the mainboard was found to be in good working order. The system fired right up with the Ti CPU, some RAM, and a video card installed.

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Kernel Hack Brings Windows XP To The 486

June 23, 2024 by 20 Comments

The venerable Intel 486 was released in 1989 as the successor to the extremely popular Intel 386. It was the minimum recommended processor for Windows 98.  (Surprisingly, the Windows 95 minimum was a 386!)  But by the time XP rolled around, you needed at least a 233 MHz Pentium to install. Or at least that was the case until recently when an extremely dedicated user on MSFN named [Dietmar] showed how he hacked the XP kernel so it could run on the classic chip!

The biggest issue preventing XP from working on earlier processors is an instruction introduced on the Pentium: CMPXCHG8B. This instruction compares two 8-byte values and takes different actions depending on an equality test. It either copies the 8 bytes to a destination address or loads it into a 64-bit register. Essentially, it does what it says on the tin: it CoMPares and eXCHanGes some values. If you want to dig into the nitty-gritty details, you can check out this info on the instruction taken from the x86 datasheet.

Without getting too technical, know that this instruction is vital for performance when working with large data structures. This is because one instruction moves 8 bytes at a time, unlike the older CMPXCHG instruction, which only moves a single byte. Essentially, [Dietmar] had to find every usage of CMPXCHG8B and replace it with an equivalent series of CMPXCHG instructions.

On a side note, the once well-known and devastating Pentium F00F bug was caused by a faulty encoding of the CMPXCHG8B instruction. This allowed any user, even unprivileged users, to completely lock up a system, requiring a full reset cycle!

So [Dietmar] was successful, and now you can run the German version of Windows XP on either a real 486 or an emulated one. The installer is available on the Internet Archive and there’s a detailed video below demonstrating installing it on the 86Box virtual machine host.

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