> 
> Sorry, I can't remember the beginning: how do you get to 6281856 ? If
> below (63s/16h/6244c) is right, then 63*16*6244=6293952 should be the
> magic number, and something like

I didn't remember the cylinder count, it is 6232.

> 
> thisdisk|Harald's disk:\
>         :dt=ST506:se#512:ns#63:nt#16:sc#6244:nc#4092:\
>         :pa#6293952:oa#0:ta=4.2BSD:ba#8192:fa#1024:\
>         :pc#6293952:oc#0:\
>         :pd#6293952:od#0:
> 

I don't understand what you have done with sc and nc;

The docu for disktab states:
---------
nt        num      Number of tracks per cylinder
nc        num      Total number of cylinders on the disk
sc        num      Number of sectors per cylinder, nc*nt default
---------

On my disk this is 

nt=number of heads= 16
nc=number of cylinders = 6232

Which gives sc=nc*nt=6232*16 = 99712 (which I'll ignore, since it is
default)

Also I observe that all entries in disktab has "ty=winchester", so I'll
throw that in as well.

I don't know the impact of using "ba#8192:fa#1024", but I'll assume this
is the best for this disk. The disktab that comes with the system
sometimes use "bh#4096:fh#512", I take it this is a way to get rid of
the "warning [blahblah] unused" message, but degrades performance.

I believe that would make it:

thisdisk|Harald's disk:\
        :dt=ST506:ty=winchester:se#512:ns#63:nt#16:nc#6232:\
        :pa#6281856:oa#0:ta=4.2BSD:ba#8192:fa#1024:\
        :pc#6281856:oc#0:\
        :pd#6281856:od#0:

Todd: I am sure your observation about bios ignoring the upper bits is
correct. When I used Windows NT on this machine, I had one partition of
20 MB's to boot from, when NT booted it saw the info the way it was
specified in the BIOS, and was able to use the rest of the disk as a
large disk. Using a fake number of cylinders would also work I'd
believe.

Thanks,

Harald.