I forget what I last reported, but the latest is that I added support
for "unit 1" in addition to "unit 0". It was just a few minutes' work in
the laptop code.
Also added support for turning logging on/off on the fly in the DOS

I experimented with changing the DX driver to increase the size of the
'disk'. It mostly worked, but I found that the interleave logic in the
driver does not handle very large capacities.
So then it occurred to me that if I am changing the driver anyway,
interleave is not needed. Also, I don't have to be limited to 128-byte
transfers -- I can just as easily do 512-bytes (1 block), since this is
the unit of size that RT is really interested in.
So, now I'm working on a new driver called "XX". It should be faster,
since the overhead is reduced, and it will be simpler than the DX
Of course, the original DX driver will still be supported, since none of
this involves any hardware changes.