The RF11 device controller from DEC for the UNIBUS is an early secondary storage controller for the PDP-11. It can interface with up to eight RS11 fixed-head disk drives; each has a capacity of 512 Kbytes of storage.
Unlike all other DEC disk controllers, the RF11 can read or write individual words; this was itended to allow optimal use of both disk space and main memory (e.g. during swapping).
Like many of the early large peripheral controllers for the PDP-11, it was a large custom wire-wrapped backplane which bolted into the front of a 19 inch rack, such as an H960; into it plugged about 40 small M-Series FLIP CHIPs.
A single rack held the controller, its power supply, and one or more drives (up to two in that rack), along with an indicator panel at the top of the rack.
Device registers
| Register |
Abbreviation |
Address
|
| Disk Control Status Register |
DCS |
777460
|
| Word Count Register |
WC |
777462
|
| Current Memory Address |
CMA |
777464
|
| Disk Address Register |
DAR |
777466
|
| Disk Address Extension Error Register |
DAE |
777470
|
| Data Buffer Register |
DBR |
777472
|
| Maintenance Register |
MA |
777474
|
| Address of Disk Segment Register |
ADS |
777476
|
777460: Disk Control Status Register (DCS)
| Error |
Freeze |
Write Check |
Data Parity |
NXD |
Write Lockout |
Missed Xfer |
Disk Clear |
Control Ready |
Interrupt Enable |
Ext Mem |
Maintenance |
Function Register |
Go
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
777462: Word Count Register (WC)
| WC15 <---> WC00
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
777464: Current Memory Address Register (CMA)
| BA15 <---> BA01 |
Unused
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
777466: Disk Address Register (DAR)
| Track Address |
Word Address
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
777470: Disk Address Extension Error Register (DAR)
| Address Parity |
Timing Track Error |
Unused |
NXM |
Unused |
Current Memory |
Data Req Late |
Unused |
Disk Addr Ovflo |
Disk Address |
Track Address
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
The low five bits of this register are actually an extension to the Disk Address Register (above).
777472: Data Buffer Register (DBR)
| DB15 <---> DB00
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
777474: Maintenance Register (MA)
| Unused |
Data |
Timing |
Unused |
Data Track |
Timing C |
Timing B |
Timing A
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
777476: Address of Disk Segment Register (ADS)
| Unused |
Disk Segment Address
|
| 15
|
14
|
13
|
12
|
11
|
10
|
09
|
08
|
07
|
06
|
05
|
04
|
03
|
02
|
01
|
00
|
External links
