sbd1 != sdb1
oops, yes, as far as I remember there was a perception test for exactly this one :-)
And apparently Roberts hint was completely correct. If there is anywhere another iso
image anywhere on the drive, it is necessary to specify the full path explicitely. For
ease of typing I had renamed CorePlus-4.4tc3.iso to CorePlus.iso and moved it to the
root. But there was another image named A2.iso in the root. I moved that to a
subdirectory without renaming it to a different extension. This did not work.
no extensions are found and it boots to the command prompt, when there is yet
another iso image in another directory, but if that iso image is also renamed to
a different extension, it is found and the extension are loaded.
Almost identical to specifying the full path, i.e. the following additional options
iso=sdb1/CorePlus.iso waitusb=5 kmap=qwertz/de-latin1