RF(4) Kernel Interfaces Manual RF(4)
rf - RF11/RS11 fixed-head disk file
This file refers to the concatenation of all RS-11 disks.
Each disk contains 1024 256-word blocks. The length of the combined RF
file is 1024x(minor+1) blocks. That is minor device zero is taken to
be 1024 blocks long; minor device one is 2048, etc.
The rf0 file accesses the disk via the system's normal buffering mecha-
nism 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 name of the raw RF file is rrf0. The same minor
device considerations hold for the raw interface as for the normal
In raw I/O the buffer must begin on a word boundary, and counts should
be a multiple of 512 bytes (a disk block). Likewise seek calls should
specify a multiple of 512 bytes.
The 512-byte restrictions on the raw device are not physically neces-
sary, but are still imposed.