TODO, important, particularly for crops, mfcr and mtcr, what elwidth
even means. instead it may be possible to use the bits as extra indices
-(EXTRA6) to access the full 64 CRs. TBD, several ideas
+(add to EXTRA2/3) to access the full 64 CRs at the bit level. TBD, several ideas
The actual width of the CRs cannot be altered: they are 4 bit. Also,
for Rc=1 operations that produce a result (in RT or FRT) and corresponding CR, it is