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AMD's legendary K5, its first independently-designed processor, is being removed from the Linux kernel — 4.3-million-transistor chip gets the axe because it lacks Time Stamp Counter (TSC) support, making it a coding burden
AMD’s landmark K5 processor family will no longer be supported by Linux when kernel version 7.2 arrives. The Linux-watchers at Phoronix noticed the forced retirement of the venerable K5 in a recent patch designed to “remove support for TSC-less Pentium variants.” The lack of TSC (Time Stamp Counter) in the K5 apparently makes it a burden for developers to support in the kernel.
The K5 holds a special place in AMD history as the firm’s first independently designed x86 processor. However, it wasn’t a very popular processor as it arrived late, then offered lackluster performance in the competitive environment it joined.
AMD’s shiny homegrown 4.3M transistor chip featured a “RISC-based internal architecture that decoded x86 instructions into micro-instructions before executing them,” we noted in a 2008 retrospective. However, launch SKUs in 1996 were limited to clocks from 75 MHz to 133 MHz, and, due to being late, Intel’s Pentium line was already faster. AMD still managed to get an edge on the Cyrix 6x86, though.
As was de rigueur at the time, these AMD K5 chips were sold with a ‘performance rating’ (PR) figure, suggesting an integer performance comparison with an Intel Pentium with the indicated clock speed. For example, a second revision K5 with a 116 MHz clock was marketed as a K5 PR166. Enthusiasts don’t like this kind of obfuscation, even when it is clearly on the surface. We also note that this era marked the introduction of the heatsink and fan as a CPU-partnering necessity.
Intel i486, AMD Elan SoCs, and AMD Geode CPUs also put out to pasture
We reported a month ago that Linux devs had started to remove support for the 37-year-old Intel i486 CPU in patches destined for the Linux 7.1 kernel. That was probably a bigger deal than today’s AMD K5 news, as many more of these processors were sold.
Other lesser-known processor lines have also been retired from Linux support, but are still worth a mention for the sake of completeness. Specifically, the AMD Elan (i486‑class, TSC‑less) SoC for embedded systems which first launched in 1995, looks set to be retired in Linux 7.2. Similarly the AMD Geode x86 embedded processors (early 2000s Elan replacements) will be cut off from Linux support from Linux kernel 7.2.
With no end in sight for the RAMpocalypse, it is a little sad to see older hardware getting dropped from support. However, machines packing these retired processors can still be used in fun projects where a fully up-to-date security-hardened internet-connected patched OS isn’t essential.
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Mark Tyson is a news editor at Tom's Hardware. He enjoys covering the full breadth of PC tech; from business and semiconductor design to products approaching the edge of reason.
Erm... Larabel used a K5 processor image because it's from the same period, but discussion in the article mention that K5 does have a TSC. The patch itself doesn't mention the K5 explicitly, only the removal of non-TSC CPU support.
Some people confused on some old AMD processor models. The only AMD processor mod who got removed from the new Linux kernel was AMD 5k86 processors which comprised of several line up including AMD Elan embedded processor.
Some people confused on some old AMD processor models. The only AMD processor mod who got removed from the new Linux kernel was AMD 5k86 processors which comprised of several line up including AMD Elan embedded processor.
True - 5k86 is nothing but a souped up 486. It was a great upgrade over a DX2/66 at the time, but has little to do with the K5.
AMD: Our CPUs have X feature.
The Internet: AMD CPU doesn't have X feature.
Mr Tom: "Repeats the Internet" without confirmation or validation from respective parties even though there are clearly written discrepancies everywhere, in wiki articles, in manual documentations, in community experiences and citation.
NO! You are all wrong, Mr Tom and the internet is correct.
Regarding the K5: not only was it the first AMD-only x86 design, it was also the last and only, not the first in long line of x86 progeny, but a botched attempt that got put out to pasture almost immediately.
The K6 and everything that came later was based on the NexGen design AMD bought in 1996, one of the smartest moves ever made by Jerry Sanders.
Not that I or most others particularly cared at the time, I guess it was mostly for lack of measurable extra performance that I skipped it, moving from an AMD Am5x86, essentially a 133-MHz 80486 to practically every K6 variant ever made: the wonders of the Socket 7 and the relative affordability of just swapping a CPU allowed me to swap them much like a pair of jeans.
In fact, I might have sacrificed jeans for CPUs, which might explain how my fortunes in IT and the mating circuit diverged.
