RF11 — RS11 fixed-head disk

The RF11 is DEC’s controller for the RS11 DECdisk, a fixed-head disk with a head for every track and so no seek: each RS11 holds 262,144 words, and one controller takes up to eight of them. It is the disk the first editions of UNIX ran from. QUniLator emulates the controller, listed as rf, and one device, rs0, that stands for the whole set of RS11 disks behind it. Its image is one file holding all of them, word after word.

UNIBUS · UniBone

The RF11 is a UNIBUS controller: base address 777460, vector 204, bus request level 5, backplane slot 12. Its transfers reach 18-bit addresses.

QBUS · QBone

The QBone carries the same controller, at 17777460 (177460 as a program names it), with the same vector, level and slot. Its transfers reach the first 256 KB of memory.

What the machine sees

Registers	DCS, WC, CMA, DAR, DAE, DBR, MAR and ADS, at the base address and the seven words above it
Disk	Up to 2,097,152 words, addressed by word: DAR holds the low 16 bits, DAE the track and disk select bits above them
Functions	Read, Write and Write Check, with an interrupt when the transfer is done. The disk address and, unless DAE inhibits it, the memory address advance with the transfer
Errors	Nonexistent disk for an address past the last word, nonexistent memory, which also sets FRZ, and write check
Timing	A transfer takes 16 µs a word

The maintenance register takes what is written to it, and the address-of-disk- segment register, which on a real RS11 follows the platter’s rotation, reads 0.

Using it

1. Add rf on the Configurations screen, and the drive rs0 with its image.
2. Enable the controller and the drive.

The controller answers as a full set of eight disks whatever the image’s size: nonexistent disk is raised only for an address past the eighth.

What has been verified

DEC’s diagnostics ZRFB and ZRFC pass on the controller’s first version, and ZRFA runs up to its test 115. No run against the current code is recorded.

Controller parameters

It has no parameters of its own.

It also carries the parameters under parameters every card on the bus has.

Drive parameters

It has no parameters of its own.

It also carries the parameters under parameters every drive has.