V7M/man/man4/rp.4

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.TH RP 4 
.SH NAME
rp \- RP-11/RP03 moving-head disk
.SH DESCRIPTION
The files
.I "rp0 ... rp7"
refer to sections of RP disk drive 0.
The files
.I "rp8 ... rp15"
refer to drive 1 etc.
This allows a large disk to be broken up
into more manageable pieces.
.PP
The origin and size of the pseudo-disks on each drive are
as follows:
.PP
.br
	disk	start	length
.br
	0	0	9600
.br
	1	9600	8000
.br
	2	17600	7400
.br
	3	25000	55000
.br
	4	0	80000
.br
	5-7	unassigned
.PP
Thus rp4 covers the whole drive,
while rp0, rp1, rp3 can serve usefully as a root, swap, and
mounted user file system respectively.
The disk rp2 covers a mounted file system
containing the system sources.
.PP
The
.I rp
files
access the disk via the system's normal
buffering mechanism
and may be read and written without regard to
physical disk records.
There is also a `raw' interface
which provides for direct transmission between the disk
and the user's read or write buffer.
A single read or write call results in exactly one I/O operation
and therefore raw I/O is considerably more efficient when
many words are transmitted.
The names of the raw RP files
begin with
.I rrp
and end with a number which selects the same disk
section as the corresponding
.I rp
file.
.PP
In raw I/O the buffer must begin on a word boundary.
.SH FILES
/dev/rp?, /dev/rrp?
.SH SEE ALSO
hp(4)
.SH BUGS
In raw I/O
.I read
and
.IR write (2)
truncate file offsets to 512-byte block boundaries,
and
.I write
scribbles on the tail of incomplete blocks.
Thus,
in programs that are likely to access raw devices,
.I read, write
and
.IR lseek (2)
should always deal in 512-byte multiples.