View source for ML11 MOS Memory System

The '''ML11''' was a [[MASSBUS]] [[solid state]] [[mass storage]] device. Its basic format was 18-[[bit]] [[word]]s (for use in [[PDP-10]] and [[PDP-15]] machines), but it could be used in [[PDP-11]]s and [[VAX]]en, which simply ignored the two high bits.

It attached to any MASSBUS controller, e.g. [[RH11 MASSBUS controller|RH11]] ([[UNIBUS]]), [[RH70 MASSBUS controller|RH70]], or [[RH780 Massbus Adapter|RH780]]. Up to 8 devices total can be attached to any MASSBUS controller.

The initial configuration, using 16Kbx1 [[Dynamic RAM|DRAM]] [[integrated circuit|chip]]s, 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 [[cyclic redundancy check|CRC]] [[error-correcting code|ECC]].

==Registers==

In the table below, 'Number' is the MASSBUS [[register]] number; the 'Address' is the UNIBUS [[address]] (e.g. when using an RH11).

{| class="wikitable"
! Location !! Number !! Name !! Function
|-
| 000 || 00 || MLCS1 || Control and Status 1
|-
| 002 || &nbsp; || MLWC || Word Count
|-
| 004 || &nbsp; || MLBA || Bus Address
|-
| 006 || 05 || MLDA || Desired Address
|-
| 010 || &nbsp; || 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 || &nbsp; || 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 || &nbsp; || MLBAE || Bus Address Extension@
|-
| 052 || &nbsp; || MLCS3 || Control and Status 3@
|}

@ = RH70 only, not RH11

The [[address]]es shown are based at 0776400 for the first ML11 in a system.

==Implementation==

The basic system consisted of a number of [[DEC card form factor|hex]] [[printed circuit board|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 cable]]s 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:

{| class="wikitable"
! !! colspan="6" | Connector
|-
! Slot !! A !! B !! C !! D !! E !! F
|-
| 1 || colspan="2" style="text-align:center;" | Unused || colspan="2" style="text-align:center;" | M5903 MASSBUS || colspan="2" style="text-align:center;" | Unused
|-
| 2 || colspan="2" style="text-align:center;" | Unused || colspan="2" style="text-align:center;" | M5903 MASSBUS || colspan="2" style="text-align:center;" | Unused
|-
| 3 || colspan="2" style="text-align:center;" | Unused || colspan="2" style="text-align:center;" | M5903 MASSBUS || colspan="2" style="text-align:center;" | Unused
|-
| 4 || colspan="6" style="text-align:center;" | M7361 asynchronous control
|-
| 5 || colspan="6" style="text-align:center;" | M7362 synchronous control
|-
| 6 || colspan="6" style="text-align:center;" | M7363 array data
|-
| 7 || colspan="6" style="text-align:center;" | M7357/58 arrray board 0
|-
| 8-21 || colspan="6" style="text-align:center;" | Arrray boards 1-14
|-
| 22 || colspan="6" style="text-align:center;" | 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

[[Category: MASSBUS Devices]]