> Its on an AHA1540B. I have enabled the BIOS, and it finds the disk all
> right.
> If so, which geometry should I use for disklabelling? Or: How can I
> determine the logical geometry that the AHA BIOS reports?

Use the Adaptec logical geometry:  32 sectors/track, 64 tracks/cylinder.
This works out to a very convenient megabyte per cylinder, so I use it
even when I don't have to (non-DOS disks); no modern disk has a fixed number
of blocks per cylinder over the whole disk, anyway, so you're guaranteed
that the FFS optimizations are going to be a bit off, anyway.