NC> Come to think of it, I hadn't realised RISC OS 4 had
  NC> actually started shipping. Certainly it seemed to go out
  NC> with a low profile, no? I never heard news of it on the
  NC> Acorn Cyber Village or anything. 
   
RISCOS 4 started shipping on July 1st, although it seems to have
taken a long time to reach anybody. I think that there was
something about it on the Cybervillage site at the time.
    
I have looked at the problem with BtRiscBSD further. I found an
older version of BtRiscBSD on the 'Risc Disc volume 3', version
2.87. That exhibited the same problem and came with the source (I
must have deleted the 2.88 source as I thought I would never need
it). Anyway, I played around with the program 'bsdbooter' and
managed to get around the dynamic area problem by changing
'KERNAREA' to -1 (so that RISCOS allocated an area number).
  
Unfortunately I then hit the real showstopper.
 
The RISCOS 4 memory map has changed. 'BtRiscBSD' plays around
with some memory at address 0x2c00000. This address is hard coded
in the program. Under RISCOS 4 there is no longer anything
accessible at that address (at least, not in user mode). I note
from the RISCOS 3 PRMs that that address is marked as 'reserved
for system use'. Now, looking at the file 'kernel.html' that Acorn
put on the Clan web site just before Black Thursday, there is a
section entitled '1.8 Logical memory map changes'. There are a
couple of things of interest here:
 
  'Maximum RMA size is increased from 11M to 15M'
 
  'Some kernel workspace is better protected from user access'
 
The first point is interesting: refering to the RISCOS 3.5 memory
map, the RMA starts at the 33 meg mark and extends to 44 meg, that
is, is eleven megabytes in size. The reserved area that BtRiscBSD
fiddles with starts at the 44 meg line and extends for four
megabytes. Now, 11+4 = 15... I do not have a RISCOS 4 memory map,
but I wonder if the area BtRiscBSD looks at is now part of the
RMA? Addesses in the RMA still start at 0x2100000, that is, at the
33 meg line. Unfortunately I cannot check if the Clan area still
exists, or if the RISCOS 4 documentation there is still accessible
otherwise I would grab the memory map. Perhaps someone else could
do that. I guess it could be the second point that has tripped up
the program but the first one fits two well, IMHO.
  
The UnixFS one seems to me to be more clear cut. RISCOS ltd would
appear to have used a different partition type for 'F+' format
disks and UnixFS does not recognise it. I guess that this would
be quite trivial to fix if the partition type was known.
  
Dave
 
 
 
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