I am not sure which CPUs exactly the article is refering to with those early i586 CPUs, but I do remember those Cyrix 6x86/6x86MX CPUs. When it comes to Linux, they were always treated as 486-class CPUs because they were missing some instructions required to be considered 586-class. On the other hand their architecture was actually quite modern, like a 686 CPU with out-of-order execution. The 6x86MX also supported the CMOV instruction which is usually associated with 686-class CPU. Quite strange CPUs from today’s perspective.
VIA also had some CPUs (certain VIA C3 CPUs) that the Linux kernel always treated as 486-class CPUs due to some missing 586 instructions.
AMD’s Am5x86 CPUs were rebranded 486 CPUs, while AMD’s K5 was an early 586 CPU that might fall into that early 586 category due to missing instructions. AMD’s later K6 CPUs should support all Pentium instructions afaik (but not CMOV like the Cyrix CPUs did).
Then you have the NexGen Nx586, which is arguably 386-like in having no FPU, but ended up being the ancestor of most modern x86 CPUs by decomposing complex operations into RISC-esque micro-ops.
I am not sure which CPUs exactly the article is refering to with those early i586 CPUs, but I do remember those Cyrix 6x86/6x86MX CPUs. When it comes to Linux, they were always treated as 486-class CPUs because they were missing some instructions required to be considered 586-class. On the other hand their architecture was actually quite modern, like a 686 CPU with out-of-order execution. The 6x86MX also supported the CMOV instruction which is usually associated with 686-class CPU. Quite strange CPUs from today’s perspective.
VIA also had some CPUs (certain VIA C3 CPUs) that the Linux kernel always treated as 486-class CPUs due to some missing 586 instructions.
AMD’s Am5x86 CPUs were rebranded 486 CPUs, while AMD’s K5 was an early 586 CPU that might fall into that early 586 category due to missing instructions. AMD’s later K6 CPUs should support all Pentium instructions afaik (but not CMOV like the Cyrix CPUs did).
Then you have the NexGen Nx586, which is arguably 386-like in having no FPU, but ended up being the ancestor of most modern x86 CPUs by decomposing complex operations into RISC-esque micro-ops.