It is all part of a cunning plan which will make older versions of the 32-bit architecture obsolete.
Last year Debian decided to increase the minimum CPU features for the i386 architecture to 686-class in the Stretch release cycle. This meant dropping support for 586-class and hybrid 586/686 processors. Support for 486-class processors happened the Squeeze release.
The changes were put into the Linux kernel packages starting with Linux 4.3, which was uploaded to Unstable in December last year. It will all be completed when the Stable version, dubbed Jessie, goes live.
But this means that there is a list of processors which will no longer be supported after Debian "Jessie” which include:
* AMD K5, K6, K6-2 (aka K6 3D), K6-3
* DM&P/SiS Vortex86, Vortex86SX
* Cyrix III, MediaGX, MediaGXm
* IDT Winchip C6, Winchip 2
* Intel Pentium, Pentium with MMX
* Rise mP6
* VIA C3 'Samuel 2', C3 'Ezra'