RK11 disk controller

The RK11 series of controllers for the UNIBUS and QBUS are for the earlier RK moving-head magnetic disk drives (RK02-RK05), all based on the IBM 2315 drive and pack. (The later RK06 and RK07, and their controller, the RK611, are a different drive and pack.)

There are several models of the RK11, which are basically identical in their programming interface; differences between them are discussed in the sections on the individual models (below).

The UNIBUS RK11's all connect to the RK drive through a BC11A cable, the standard UNIBUS cable.

RK11-C

Main article: RK11-C disk controller

Like many of the earlier large peripheral controllers for the PDP-11, the RK11-C was a large custom wire-wrapped backplane which bolts into the front of a 19 inch rack, such as an H960; into it plugged about 40 small M-Series FLIP CHIPs.

RK11-D

The RK11-D was a re-implementation of the RK11-C on four quad cards (M7254-7), which plugged into a custom-wired quad-wide hex-high system unit backplane, for a BA11 slide-out mounting box.

It was program-compatible with the RK11-C, except that the RK11-D did not contain the Maintenance Register of the earlier controller. In the RK11-D, the bus location of the MR responds, but according to the prints, it reads as zero, and written data is ignored.

RK11-E

The RK11-E (sometimes called the RK15) was a variant of the RK11-D which supported 18-bit data; it was used with the PDP-15. It used the same cards as the RK11-D, with a jumper selection for 18-bit operation, and a different clock crystal.

It was used with the UC15 Unichannel, which used a PDP-11/05 acting as a slave to the PDP-15 via shared memory; the RK11-E was plugged into the UNIBUS on the PDP-11. It used the two UNIBUS parity lines for the two extra data bits. The two extra bits were not used by the PDP-11 or its memory, but went through the MX15-B Memory Multiplexer, directly to the PDP-15's memory.

RKV11-D

The RKV11-D is a variant of the RK11-D for the QBUS (the others are all UNIBUS).

It uses three of the four cards of the RK11-D (M7254-6), along with a different custom quad-wide quad-high system unit backplane, and a replacement fourth card (M7268) which is connected via ribbon cables to two dual cards, one of which (M7269) plugs into a QBUS backplane slot, and the other (M993-YA) into the first RK05 drive.

It is programming compatible with the RK11-D, except that it only supports Q16 QBUS mode, so the two extended memory bits in the CSR have no effect; they may be read and written, but are not connected to anything.

Device registers

Register	Abbreviation	Address
Drive Status Register	RKDS	777400
Error Register	RKER	777402
Control Status Register	RKCS	777404
Word Count Register	RKWC	777406
Current Bus Address Register	RKBA	777410
Disk Address Register	RKDA	777412
Maintenance Register	RKMR	777414
Data Buffer Register	RKDB	777416

777400: Drive Status Register (RKDS)

Drive Ident.			DPL	HDEN	DRU	SIN	SOK	DRY	ARDY	WPS	SC=CA	Sector Counter
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777402: Error Register (RKER)

DRE	OVR	WLO	SKE	PGE	NXM	DLT	RTE	NXD	NXC	NXS				CSE	WCE
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777404: Control Status Register (RKCS)

ERR	H.E.	SCP	M	IBA	FMT	R/WA	SSE	RDY	IDE	EX. MEM		FUNCTION			GO
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777406: Word Count Register (RKWC)

WC15 <---> WC00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777410: Current Bus Address Register (RKBA)

BA15 <---> BA00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777412: Disk Address Register (RKDA)

DRIVE SELECT			CYLINDER ADDRESS								SUR	SECTOR ADDRESS
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777414: Maintenance Register (RKMR)

M. RCP	M. RDP	M. SPS	M. ADA	M. LAI				M. DRY	M. R/W/S			MAINT. SECTOR COUNTER
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

777416: Data Buffer Register (RKDB)

DB15 <---> DB00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

PDP-11 bootstraps

Disk 0

Address	Data	Mnemonic	Description
1000	012700	MOV #177406,R0	Move the address of the Word Count register into R0
1002	177406		(constant)
1004	012710	MOV #177400,(R0)	Move block size (negative) into Word Count register
1006	177400		(constant)
1010	012740	MOV #5,-(R0)	Move 'Read Go' command into CSR
1012	000005		(constant)
1014	105710	TSTB (R0)	Test for 'Done' bit in CSR
1016	100376	BPL 1014	Jump backward if not set
1020	005007	CLR PC	Start loaded bootstrap with jump to 0

Note that the INIT pulse caused by hitting the 'Start' button will clear the Bus Adddress register, so the loaded block will be placed at location 0.

Disk n

This bootstrap will boot from any disk in a daisy-chained multi-drive configuration. Memory location octal 1006 contains the unit number, as follows:

Address Data Mnemonic Description 1000 012700 MOV #177406, R0 Store the address of the Word Count register in r0 1002 177406 (constant) (Which is 177406) 1004 012760 MOV xxxxxx, 000004(R0) Store the disk ID number in the Disk Address register 1006 xxxxxx (disk ID number) The disk number goes here. 1010 000004 (index) 1012 012700 MOV #177406, R0 Store the addresss of the Word Count register in r0 1014 177406 (constant) (Which is 177406) 1016 012710 MOV #177400, (R0) Store 177400 into the Word Count register, 1020 177400 (constant) meaning that octal 400 words are to be read. 1022 012740 MOV #000005, -(R0) Store 5 into the Control Status register 1024 000005 (constant) selecting the function "read" with 4, and "go" with 1 1026 105710 TSTB (R0) Test the Control Status Register (upper) byte 1030 100376 BPL *-1 Repeat if it's positive, that is Control Ready is cleared 1032 005007 CLR PC If not, clear the Program Counter (essentially, jump to 0)

Value Unit 020000 Unit 1 040000 Unit 2 060000 Unit 3 100000 Unit 4 120000 Unit 5 140000 Unit 6 160000 Unit 7

Documentation

RK11-C manual, 1971

RK11-C schematics, February 1971

EK-RK11D-MM-002, RK11-D Maintenance Manual