Update README.md

README.md

@@ -17,6 +17,7 @@ $ ulimit -n 2048
 
 before running `piscem`.
 
+- **The pre-compiled executables (including those installed via bioconda)** require that the underlying processor support [the BMI2 instruction set](https://en.wikipedia.org/wiki/X86_Bit_manipulation_instruction_set). If you are running on a CPU from ~2012 or earlier, these instructions may not be available and the pre-compiled executable may not work. In that case, you should compile from source using the `NO_BMI2` environement variable (i.e. `NO_BMI2=TRUE cargo build --release`).
 
 Building
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