View source for 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.

==Early RK11 version==

Although the [[RK11-C disk controller|RK11-C]] (below) is the earliest documented version, there are a few clues which indicate that there was an earlier version (one for which no documentation remains).

First, there is an image of a [[DEC indicator panel]] (see below) which seems to be from a pre-RK11-C; it clearly seems to be an RK11 panel of some sort, but the pinout of the RK11-C indicator panel connector ("RK11-C Indicator Connectors: RK11-C-23") has differences.

In particular, on the panel in the image, the lower right line of lights on the panel shows 3 bits of Major State; on the RK11-C prints (on connector B32) there are 5 individual bits (Postamble, Checksum, Data, Header, Preamble). To explore this further, on the "Major States" RK11-C print (RK11-C-04), in the upper left corner, there is a row of 6 flops, each labeled with one of those states (plus one for 'Idle'), arranged in a chain - the output of each driving an individual light. However, the 3 bits for 'Major State' on the display panel imply it is binary coded - likely implemented with a counter.

Also, the signal "COUNT MSR" (likely 'Major State Register') is exactly what one would expect to see if the major state had previously been held in a counter, not a string of flops. It makes no sense to expend the effort synthesize that signal (on the next page, RK11-C-05, "MSR Control") when the individual signals which go into it could have been used as is to clock each flop in the chain.

A reasonable ''guess'', in light of these facts, is that in some previous version, a counter had been used, but had had a problem of some sort, and had therefore been replaced by the string of flops. (The reason is unknown, but perhaps it was a binary counter, not [[Gray code]], and the decoding into states was producing glitches.)

A plausible scenario is that such an earlier version was produced in very small numbers - perhaps as prototypes, only internal to DEC. (If there had been problems with glitches in the major state counter, they would not have wanted to release it as a product.) Or if it was released as a product, perhaps they were all recalled and replaced with RK11-C's.

In this regard, it is interesting to note the DEC Spare Module Handbook, lists only the RK11-C and -D, but '''does''' list the [[KT11-B]], a ''rara avis'' indeed. This argues that the predecessor did not exist 'in the wild'.

==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-wrap]]ped [[backplane]] which bolts into the front of a 19 inch rack, such as an [[H960]]; into it plugged about 40 small M-Series [[FLIP CHIP]]s.

==RK11-D==

The RK11-D was a re-implementation of the RK11-C on four [[DEC card form factor|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==

{| border=1
! 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)===

{{16bit-header}}
| colspan=3 | Drive Ident. || DPL || HDEN || DRU || SIN || SOK || DRY || ARDY || WPS || SC=CA || colspan=4 | Sector Counter
{{16bit-bitout}}

===777402: Error Register (RKER)===

{{16bit-header}}
| DRE || OVR || WLO || SKE || PGE || NXM || DLT || RTE || NXD || NXC || NXS || colspan=3 | || CSE || WCE
{{16bit-bitout}}

===777404: Control Status Register (RKCS)===
{{16bit-header}}
| ERR || H.E. || SCP || M || IBA || FMT || R/WA || SSE || RDY || IDE || colspan=2 | EX. MEM || colspan=3 | FUNCTION || GO
{{16bit-bitout}}

===777406: Word Count Register (RKWC)===
{{16bit-header}}
| colspan=16 | WC15 <---> WC00
{{16bit-bitout}}

===777410: Current Bus Address Register (RKBA)===
{{16bit-header}}
| colspan=16 | BA15 <---> BA00
{{16bit-bitout}}

===777412: Disk Address Register (RKDA)===
{{16bit-header}}
| colspan=3 | DRIVE SELECT || colspan=8 | CYLINDER ADDRESS || SUR || colspan=4 | SECTOR ADDRESS
{{16bit-bitout}}

===777414: Maintenance Register (RKMR)===
{{16bit-header}}
| M. RCP || M. RDP || M. SPS || M. ADA || M. LAI || colspan=3 | || M. DRY || M. R/W/S || colspan=2 | || colspan=4 | MAINT. SECTOR COUNTER
{{16bit-bitout}}

===777416: Data Buffer Register (RKDB)===
{{16bit-header}}
| colspan=16 | DB15 <---> DB00
{{16bit-bitout}}


==PDP-11 bootstraps==

===Disk 0===

{| border=1 
! Address !! Data !! Mnemonic !! Description
|- style="background-color: #ccccdd;"
|1000||012700||MOV #177406,R0           ||Move the address of the Word Count register into R0
|- style="background-color: #ccccff;"
|1002||177406||                         || (constant)
|- style="background-color: #ccccdd;"
|1004||012710||MOV #177400,(R0)         ||Move block size (negative) into Word Count register
|- style="background-color: #ccccff;"
|1006||177400||                         || (constant)
|- style="background-color: #ccccdd;"
|1010||012740||MOV #5,-(R0)        ||Move 'Read Go' command into CSR
|- style="background-color: #ccccff;"
|1012||000005||                         || (constant)
|- style="background-color: #ccccdd;"
|1014||105710||TSTB (R0)                ||Test for 'Done' bit in CSR
|- style="background-color: #ccccff;"
|1016||100376||BPL 1014                  ||Jump backward if not set
|- style="background-color: #ccccdd;"
|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:
<table>
<tr>
<td>
{| border=1
! Address       !! Data         !! Mnemonic                     !! Description
|- style="background-color: #ccccdd;"
| 1000          || 012700       || MOV #177406, R0              || Store the address of the Word Count register in r0
|- style="background-color: #ccccff;"
| 1002          || 177406       || (constant)                   || (Which is 177406)
|- style="background-color: #ccccdd;"
| 1004          || 012760       || MOV xxxxxx, 000004(R0)       || Store the disk ID number in the Disk Address register
|- style="background-color: #ccccff;"
| 1006          || xxxxxx       || (disk ID number)             || The disk number goes here.
|- style="background-color: #ccccdd;"
| 1010          || 000004       || (index)                      ||
|- style="background-color: #ccccff;"
| 1012          || 012700       || MOV #177406, R0              || Store the addresss of the Word Count register in r0
|- style="background-color: #ccccdd;"
| 1014          || 177406       || (constant)                   || (Which is 177406)
|- style="background-color: #ccccff;"
| 1016          || 012710       || MOV #177400, (R0)            || Store 177400 into the Word Count register,
|- style="background-color: #ccccdd;"
| 1020          || 177400       || (constant)                   || meaning that octal 400 words are to be read.
|- style="background-color: #ccccff;"
| 1022          || 012740       || MOV #000005, -(R0)           || Store 5 into the Control Status register
|- style="background-color: #ccccdd;"
| 1024          || 000005       || (constant)                   || selecting the function "read" with 4, and "go" with 1
|- style="background-color: #ccccff;"
| 1026          || 105710       || TSTB (R0)                    || Test the Control Status Register (upper) byte
|- style="background-color: #ccccdd;"
| 1030          || 100376       || BPL *-1                      || Repeat if it's positive, that is Control Ready is cleared
|- style="background-color: #ccccff;"
| 1032          || 005007       || CLR PC                       || If not, clear the Program Counter (essentially, jump to 0)
|}
</td>
<td>
{| border=1
! Value !! Unit 
|- style="background-color: #ccccdd;"
| 020000 || Unit 1
|- style="background-color: #ccccff;"
| 040000 || Unit 2
|- style="background-color: #ccccdd;"
| 060000 || Unit 3
|- style="background-color: #ccccff;"
| 100000 || Unit 4
|- style="background-color: #ccccdd;"
| 120000 || Unit 5
|- style="background-color: #ccccff;"
| 140000 || Unit 6
|- style="background-color: #ccccdd;"
| 160000 || Unit 7
|}
</td>
</tr>
</table>

==External links==

* [http://bitsavers.trailing-edge.com/pdf/dec/pdp11/pictures/1120_RSTS-11/1120_RK_Panel_RSTS-11.jpg Image of early RK11 indicator panel]

* [http://toresbe.dreamhosters.com/redirect.php?res=bitsavers&doc=dec/unibus/EK-RK11D-MM-002.pdf EK-RK11D-MM-002, RK11-D Maintenance Manual]

[[Category:UNIBUS Storage Controllers]]
[[Category:QBUS Storage Controllers]]