the following pseudocode adapted from p850 v3.0B needs to be added to the
openpower isa pages git.libre-soc.org, probably fixedstore.mdwn for now

# Data Cache Block set to Zero

X-Form

* dcbz RA,RB

Pseudo-code:


    if RA = 0 then b <= 0
    else           b <- (RA)
    EA <- b + (RB)
    n <- block size (bytes)
    m <- log2(n)
    ea <- EA[0:63-m] || [0]*m
    m8 <- m*8
    MEM(ea, n) <- [0]*m8

Special Registers Altered:

    None



a rebuild using pywriter (see top-level Makefile) is required after adding
the pseudocode.