hexl-mode gives surprising values

[John K Smith]

Forgive me if this is an intentional feature, or
otherwise well known.

In GNU Emacs 20.2.1 (mips-sgi-irix6.2, X toolkit)
 of Tue Jul 20 1999 on waewg3
configured using `configure  mips-sgi-irix6.2'


I have a file called ssss. Using the existing UNIX tool od, 
I can view the file:


waewg5 1% od ~/ssss
od ~/ssss
0000000 043117 051115 040524 035040 051504 043040 053145 071163
0000020 064557 067040 031056 030000 000000 000000 000000 000000
0000040 000000 000000 000000 000000 000000 000000 000000 000000
*
0000120 000000 000000 000000 000001 177777 177777 177777 177777
0000140 177777 177777 177777 177777 177777 177777 177777 177777
0000160 177777 177777 177412
0000166
waewg5 2% 

I start emacs with 
    emacs --no-init-file
Then:

C-x C-f ~/ssss
M-x hexl-mode

and I see:

00000000: 464f 524d 4154 3a20 5344 4620 5665 7273  FORMAT: SDF Vers
00000010: 696f 6e20 322e 3000 0000 0000 0000 0000  ion 2.0.........
00000020: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000030: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000040: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000050: 0000 0000 0000 0001 81ff 81ff 81ff 81ff  ................
00000060: 81ff 81ff 81ff 81ff 81ff 81ff 81ff 81ff  ................
00000070: 81ff 81ff 81ff 81ff 81ff 81ff 81ff 81ff  ................
00000080: 81ff 81ff 81ff 81ff 81ff 81ff 81ff 81ff  ................
00000090: 81ff 0a                                  ...


The ff characters of the original file are being displayed as
81ff. 

Although there might be a good reason for this behaviour, I do find it
surprising.