The database I work on (ClickHouse) tries hard to stay compatible with really old hardware. The standard ARM binaries require Armv8.2 from 2016 (available in Ra

The database I work on (ClickHouse) tries hard to stay compatible with really old hardware. The standard ARM binaries require Armv8.2 from 2016 (available in Raspberry Pi 2 >=2) and x86 binaries run on hardware from around 2010 (SSE4.2 + pclmul* instructions for fast CRC). We also build (but don't test using CI) binaries for Armv8.0 and SSE2-only systems. A quick install script downloads and unpacks the right binary for the target host. I find it generally hard to strike a good balance between backwards compatibility and usage of modern CPU features in newer AArch64 generations (https://en.wikipedia.org/wiki/AArch64 https://en.wikipedia.org/wiki/AArch64). We found that there are surprisingly many institutions on a shoestring budget (universities in emerging countries) or hobbyists that can't afford to upgrade their hardware. On a technical note, what I found quite cumbersome is that the cpu flags in /proc/cpuinfo don't always correspond with the flags passed as -march= to the compiler, e.g. "lrcpc" vs "rcpc". To make all of this work, one really needs to maintain two sets of flags.