How to architecture for each physical cpu from /sys/devices?

By example, i can get the architecture of the cpu of my pc:

$ cat /sys/devices/system/cpu/modalias;
cpu:type:x86,ven0002fam0019mod0021:feature:,0000,

Ok, is x86, but what happens with 1u rackable servers where they can have 2 or 4 xeon physical sockets cpu?, how does linux make that difference?, all cpu sockets has same architecture? can have 2 differents architecture?, if the motherboard have only one architecture, the architecture is defined by motherboard?, i have heard that some models of android mobiles have CPUs with some 64-bit cores and others with 32 in same chip to save resources.