I've just committed changes to ddb which make x/m work.

I've never done much with ddb on mach (or anywhere else really) so this was 
built using my assumptions from other hexdump routines from rom monitor's
I've used in the distant past.

x/m <memory location> does as the man page suggest and prints out in hex
N memory locations (currently defaulting to 4). It also will obey the
b h l and L modifiers to print out more or less number of bytes at a time.
After 16 locations it drops to a new line so large sections can be easily
printed and viewed.

i.e.

x/m 0xa1234567
0xa1234567:     31323334                                1234

x/bm 0xa1234567
0xa1234567:     31                                      1

It's not real useful generally without repeat counts:

x/m 0xa1234567,4
0xa1234567:     31323334 fffefd50 5f200001 12345678     1234...P_ ...4Vx


I'll include the above in the man page shortly, but I wanted to get the code
in first to get a feel from anyone if they beleive this should behave 
differently in some drastic way. 

James