>> In such a case, is it possible, without too much work [...] to get >
>> 64 KB read operations?

> It depends on the driver :)
> For IDE disks for example, it's hardware [...]

And I recall from back when I worked with UNIbus VAXen that a lot of
cards had 16-bit length registers.  I've always thought MAXPHYS was a
legacy of such hardware, with it being set to 63K rather than 64K-1 to
catch small negative lengths.  (Indeed, I have fuzzy memory of a
comment saying that last.)

					der Mouse

			       mouse@rodents.montreal.qc.ca
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