RK611 disk controller
The RK611 disk controller is the UNIBUS device controller for the RK06 and RK07 moving-head magnetic removable cartridge disk drives. All data transfers are done using DMA. Data is protected with a hardware-generated and checked error-correcting code (ECC); corrections (up to 11 bits) are done in software.
Implementation
The RK611 consists of a specially wired 9-slot backplane and five hex cards; these are:
| M7900 | Unibus interface |
| M7901 | Register module |
| M7902 | Control module |
| M7903 | Data module |
| M7904 | Drive interface module |
At least three of the other slots are wired as UNIBUS SPC slots (and thus require G727 grant continuity cards to be inserted when no device is plugged into them); the status of the fourth is currently unknown. The quad slot on the end is necessarily a plain SPC slot; whether the other hex slots are MUD slots is likewise currently unknown.
One RK611 can control up to 8 drives; a flat cable plugs into a Berg connector on one of the cards, and runs to a transition adapter on the back of the rack. From there, a round cable runs to the first drive, and similar cables connect the rest of the drives, in series. A terminator must be plugged into the 'out' port of the last drive in the series.
Registers
The RK611 has no less than fifteen registers:
| Register | Abbreviation | Address |
|---|---|---|
| Control and Status Register 1 | RKCS1 | 777440 |
| Word Count Register | RKWC | 777442 |
| Bus Address Register | RKBA | 777444 |
| Disk Address Register | RKDA | 777446 |
| Control and Status Register 2 | RKCS2 | 777450 |
| Drive Status Register | RKDS | 777452 |
| Error Register | RKES | 777454 |
| Attention Summary and Offset | RKAS | 777456 |
| Desired Cylinder Register | RKDC | 777460 |
| Data Buffer Register | RKDB | 777464 |
| Maintenance Register 1 | RKMR1 | 777466 |
| ECC Position Register | RKECPS | 777470 |
| ECC Pattern Register | RKECPT | 777472 |
| Maintenance Register 2 | RKMR2 | 777474 |
| Maintenance Register 3 | RKMR3 | 777476 |
The addresses given assume the standard base address (0777440); if this is changed, so will the addresses. Note also that there is no register at 777462.
