Both failed.

Error building index:
Error in faToTwoBit, index overflow at CHR_HSCHR4_5_CTG12. The 2bit format does not support indexes larger than 4Gb,
please split up into smaller files.

[bwa_index] Update BWT... [bwt_bwtupdate_core] Failed to allocate 46629609168 bytes at bwtindex.c line 135: Cannot allocate memory
Error building index.

So, how to split genome for TwoBit and how much RAM is needed for BWA indexes? These errors are from runs on machine with 45GB RAM.