BSD 4.2 minphys() < 64K

[Henry Spencer]

> Why does minphys() in BSD 4.2 systems still limit block i/o transfers to
> 63 * 1024 bytes?  I assume that this is an ancient artifact from PDP-11
> days...

Provided the disk controller and the bus being used can cope, I can't see
any good reason to retain the restriction.  Bear in mind that most Unibus
controllers tend to use 16-bit transfer-size counts, and any Unibus I/O
is limited by the 256KB Unibus hardware address space.  For non-Unibus
controllers, I can't see any good reason for the limitation unless there
is some other stupid problem with the VAX hardware (I don't have a VAX
and don't want one).

This doesn't mean that there isn't something silly in Berklix that will
break if you remove the limit...
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,decvax,pyramid}!utzoo!henry