Up until recently, Debian users needed to understand various chip-specific flavours within each architecture. For instance -486, -k7, -k7-smp, -686, -686-smp, etc. were all under the i386 architecture (The 32bit AMD/Intel compatible architecture) and -amd64-k8, -amd64-k8-smp, em64t-p4, etc. were all under the amd64 architecture (The 64bit AMD/Intel architecture).
Recently the chip specific versions [...]
