ML11 MOS Memory System
The ML11 was a MASSBUS solid state mass storage device. Its basic format was 18-bit words (for use in PDP-10 and PDP-15 machines), but it could be used in PDP-11s and VAXen, which simply ignored the two high bits.
It attached to any MASSBUS controller, e.g. RH11 (UNIBUS), RH70, or RH780. Up to 8 devices total can be attached to any MASSBUS controller.
The initial configuration, using 16Kbx1 DRAM chips, could hold up to 4MB in 1MB increments (composed of groups of 4 storage modules); later, the use of 64Kbx1 chips expanded the maximum to 16MB. An ML11 with the former was denominated as an ML11-A; with the latter, as an ML11-B.
The memory was organized in 36-bit words, with 3 bits per word added to hold a CRC ECC.
Registers
In the table below, 'Number' is the MASSBUS register number; the 'Address' is the UNIBUS address (e.g. when using an RH11).
| Location | Number | Name | Function |
|---|---|---|---|
| 000 | 00 | MLCS1 | Control and Status 1 |
| 002 | MLWC | Word Count | |
| 004 | MLBA | Bus Address | |
| 006 | 05 | MLDA | Desired Address |
| 010 | MLCS2 | Control and Status 2 | |
| 012 | 01 | MLDS | Drive Status |
| 014 | 02 | MLER | Error |
| 016 | 04 | MLAS | Attention Summary |
| 020 | 07 | MLPA | PROM Address |
| 022 | MLDB | Data Buffer | |
| 024 | 03 | MLMR | Maintenance |
| 026 | 06 | MLDT | Drive Type |
| 030 | 010 | MLSN | Serial Number |
| 032 | 011 | MLE1 | ECC CRC Word 1 |
| 034 | 012 | MLE2 | ECC CRC Word 2 |
| 036 | 013 | MLD1 | Data Diagnostic 1 |
| 040 | 014 | MLD2 | Data Diagnostic 2 |
| 042 | 015 | MLEE | ECC Error |
| 044 | 016 | MLEL | ECC Location |
| 046 | 017 | MLPD | PROM Data |
| 050 | MLBAE | Bus Address Extension@ | |
| 052 | MLCS3 | Control and Status 3@ |
@ = RH70 only, not RH11
The addresses shown are based at 0776400 for the first ML11 in a system.
Implementation
The basic system consisted of a number of hex boards mounted in a custom 22-slot backplane (DEC part number 70-17508), all housed in a BA11-K mounting box. The basic device controller boards were:
- M7361 asynchronous control module
- M7362 synchronous control
- M7363 array data module
Initially, data storage was provided with M7357 boards, used in groups of four, each board holding 256KB; later, these were supplanted by M7358 boards, each board holding 1MB.
Three dual-width M5903 boards provided the MASSBUS interface; flat cables led from Berg connector headers on the M5903's to the MASSBUS controller.
Board locations (as seen from the board insertion side of the backplane, not the wire-wrap pin side, as is common in DEC documentation) are:
| Connector | ||||||
|---|---|---|---|---|---|---|
| Slot | A | B | C | D | E | F |
| 1 | Unused | M5903 MASSBUS | Unused | |||
| 2 | Unused | M5903 MASSBUS | Unused | |||
| 3 | Unused | M5903 MASSBUS | Unused | |||
| 4 | M7361 asynchronous control | |||||
| 5 | M7362 synchronous control | |||||
| 6 | M7363 array data | |||||
| 7 | M7357/58 arrray board 0 | |||||
| 8-21 | Arrray boards 1-14 | |||||
| 22 | M7357/58 arrray board 15 | |||||
Further reading
- ML11 User's Guide (EK-0ML11-UG) - not available online
- ML11 Technical Description (EK-0ML11-TD) - not available online
- ML11 MOS Memory System Technical Manual (EK-0ML11-TM-002) - not available online, but in microfiche
- ML11 MOS Memory System Technical Manual (EK-ML11A-TM-003) - not available online, but in microfiche
- ML11 MOS Memory System Service Guide (EK-ML11A-SV-001) - not available online, but in microfiche
