Difference between revisions of "Modified UNIBUS Device"

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'''Modified UNIBUS Device''' or '''MUD''' was [[DEC]]'s name for an I/O board slot in the [[backplane]]s of [[UNIBUS]] [[PDP-11]]s. It was a [[DEC card form factor|hex]] slot, and could hold any kind of device.
 
'''Modified UNIBUS Device''' or '''MUD''' was [[DEC]]'s name for an I/O board slot in the [[backplane]]s of [[UNIBUS]] [[PDP-11]]s. It was a [[DEC card form factor|hex]] slot, and could hold any kind of device.
  
−
It differed from the older [[Small Peripheral Controller]] slot in that it was a hex-height slot, and used the extra pins (in the A/B rows) to carry UNIBUS signals (pin-compatible with the usual dual UNIBUS slot); additional voltages (+ and -15V, -5V, and +20V); and a number of lines for communication between a parity controller, and parity-capable memory boards plugged into that backplane.
+
It differed from the older [[Small Peripheral Controller|SPC]] slot in that it was a hex-height slot, and used the pins (in the [[DEC edge connector contact identification|A-B connectors]]) to carry UNIBUS signals - mostly pin-compatible with the original dual UNIBUS slot, but there were a few important differences.  
  
−
MUD slots, like SPC slots, were wired to bring all 4 UNIBUS grant lines through the device; this was performed in rows C (for NPG) and D (for BGx), not the 'pseudo-UNIBUS' rows A/B, since the standard UNIBUS dual connector only contains one pin per grant (suitable only for an 'in' or 'out' UNIBUS connector), not separate 'grant in' and 'grant out' pins (as on the [[QBUS]]).
+
The most important was that since the standard UNIBUS dual connector only contains one pin per [[bus grant line]] (suitable only for an 'in' or 'out' UNIBUS connector), not separate 'grant in' and 'grant out' pins (as on the [[QBUS]]), a full-function UNIBUS slot is not possible with only two connectors. The MUD connectors therefore do not contain grants; those pins were recycled for other functions.
  
−
A board plugged into a MUD slot generally had a header which routed the grant (and matching request) line for the desired priority level to the on-board interrupt circuity, and passed the other grant lines through. The DMA (NPG) grant line generally had a jumper on the backplane, which had to be removed if a DMA device was plugged into the slot. Un-occupied slots needed to have a grant continuity card installed.
+
Some re-assigned pins contain a number of lines for communication between a [[parity]] controller, and parity-capable [[main memory]] boards plugged into that backplane; others carry additional [[voltage]]s (primarily for [[core memory]]).
 +
 
 +
Technically, a MUD slot only describes the A-B [[DEC edge connector contact identification|connectors]]; most backplanes also provided SPC functionality in the C-F connectors (needed for signals for [[interrupt]]s or [[Direct Memory Access|DMA]], for devices which did those), with most UNIBUS signals present in both; the combination is sometimes called a 'MUD/SPC' slot.
 +
 
 +
The [[DD11-C backplane|DD11-C]] (4-slot) and [[DD11-D backplane|DD11-D]] (9-slot) and later backplanes generally provided MUD slots, not the earlier SPC slots; however, generally the slots in these later backplanes are MUD/SPC - other than the entrance and exit slots, which have normal two-slot UNIBUS in/out in A-B, and SPC in C-F.
 +
 
 +
==Grants==
 +
 
 +
MUD/SPC slots were wired to bring all 5 UNIBUS grant lines through the device; this was performed in rows C (for NPG) and D (for BGx), not the 'pseudo-UNIBUS' rows A/B.
 +
 
 +
A board plugged into a MUD/SPC slot generally had a header which routed the grant (and matching request) line for the desired priority level to the on-board interrupt circuity, and passed the other grant lines through.
 +
 
 +
The DMA (NPG) grant line generally had a jumper on the backplane, which had to be removed if a DMA device was plugged into the slot.
 +
 
 +
Un-occupied slots needed to have a [[G7273 grant continuity card|grant continuity card]] installed.
 +
 
 +
==Added signals==
 +
 
 +
The added lines for communication between a parity controller and parity-capable memory boards were Parity Detect (used to let memory boards know that a parity controller is present); Internal SSYN (used by memory boards to let the parity controller know that their data is ready); and Parity P0 and Parity P1 (parity data).
 +
 
 +
The additional voltages were + and -15V, -5V, and +20V. Note that in some machines (the [[PDP-11/44]] and [[PDP-11/24]]) the +15V/-15 pins actually contain +12V/-12V, for use by the [[MS11-M MOS memory]] card, which needs those voltages. +15V/-15V are available in the SPC portion of some such slots.
 +
 
 +
===Pinout===
 +
 
 +
The pins which were added (changed) to create MUD are:
 +
 
 +
* AB2 - Test Point
 +
* AN1 - Parity P1
 +
* AP1 - Parity P0
 +
* AR1 - -15/12 Battery
 +
* AS1 - -15/12 Battery
 +
* AU1 - +20V (core)
 +
* AV1 - +20V (core)
 +
* AV2 - +20V (core)
 +
* BA1 - Reserved
 +
* BB1 - Reserved
 +
* BB2 - Test Point
 +
* BD1 - +5V Battery
 +
* BE1 - Internal SSYN
 +
* BE2 - Parity Detect
 +
* BV2 - -5V (core)
 +
 
 +
==Removed signals==
 +
 
 +
Since grants could not be supported in the number of pins available in a dual connector, all grant pins were removed, along with some ground pins.
 +
 
 +
===Pins===
 +
 
 +
The pins which changed function from normal UNIBUS to MUD are listed below.
 +
 
 +
* AB2 - Ground
 +
* AN1 - Ground
 +
* AP1 - Ground
 +
* AR1 - Ground
 +
* AS1 - Ground
 +
* AU1 - NPG
 +
* AV1 - BG7
 +
* AV2 - Ground
 +
* BA1 - BG6
 +
* BB1 - BG5
 +
* BB2 - Ground
 +
* BD1 - Ground
 +
* BE1 - Ground
 +
* BE2 - BG4
 +
* BV2 - Ground
 +
 
 +
==See also==
 +
 
 +
* [[DD11-P backplane]]
 +
* [[Extended UNIBUS]]
 +
* [[:Category:UNIBUS_Backplanes|UNIBUS Backplanes]]
 +
* [[G727_grant_continuity_card|G727 Grant Continuity Card]]
 +
* [[G7273_grant_continuity_card|G7273 Grant Continuity Card]]
 +
 
 +
[[Category: UNIBUS]]

Latest revision as of 15:06, 30 March 2023

Modified UNIBUS Device or MUD was DEC's name for an I/O board slot in the backplanes of UNIBUS PDP-11s. It was a hex slot, and could hold any kind of device.

It differed from the older SPC slot in that it was a hex-height slot, and used the pins (in the A-B connectors) to carry UNIBUS signals - mostly pin-compatible with the original dual UNIBUS slot, but there were a few important differences.

The most important was that since the standard UNIBUS dual connector only contains one pin per bus grant line (suitable only for an 'in' or 'out' UNIBUS connector), not separate 'grant in' and 'grant out' pins (as on the QBUS), a full-function UNIBUS slot is not possible with only two connectors. The MUD connectors therefore do not contain grants; those pins were recycled for other functions.

Some re-assigned pins contain a number of lines for communication between a parity controller, and parity-capable main memory boards plugged into that backplane; others carry additional voltages (primarily for core memory).

Technically, a MUD slot only describes the A-B connectors; most backplanes also provided SPC functionality in the C-F connectors (needed for signals for interrupts or DMA, for devices which did those), with most UNIBUS signals present in both; the combination is sometimes called a 'MUD/SPC' slot.

The DD11-C (4-slot) and DD11-D (9-slot) and later backplanes generally provided MUD slots, not the earlier SPC slots; however, generally the slots in these later backplanes are MUD/SPC - other than the entrance and exit slots, which have normal two-slot UNIBUS in/out in A-B, and SPC in C-F.

Grants

MUD/SPC slots were wired to bring all 5 UNIBUS grant lines through the device; this was performed in rows C (for NPG) and D (for BGx), not the 'pseudo-UNIBUS' rows A/B.

A board plugged into a MUD/SPC slot generally had a header which routed the grant (and matching request) line for the desired priority level to the on-board interrupt circuity, and passed the other grant lines through.

The DMA (NPG) grant line generally had a jumper on the backplane, which had to be removed if a DMA device was plugged into the slot.

Un-occupied slots needed to have a grant continuity card installed.

Added signals

The added lines for communication between a parity controller and parity-capable memory boards were Parity Detect (used to let memory boards know that a parity controller is present); Internal SSYN (used by memory boards to let the parity controller know that their data is ready); and Parity P0 and Parity P1 (parity data).

The additional voltages were + and -15V, -5V, and +20V. Note that in some machines (the PDP-11/44 and PDP-11/24) the +15V/-15 pins actually contain +12V/-12V, for use by the MS11-M MOS memory card, which needs those voltages. +15V/-15V are available in the SPC portion of some such slots.

Pinout

The pins which were added (changed) to create MUD are:

  • AB2 - Test Point
  • AN1 - Parity P1
  • AP1 - Parity P0
  • AR1 - -15/12 Battery
  • AS1 - -15/12 Battery
  • AU1 - +20V (core)
  • AV1 - +20V (core)
  • AV2 - +20V (core)
  • BA1 - Reserved
  • BB1 - Reserved
  • BB2 - Test Point
  • BD1 - +5V Battery
  • BE1 - Internal SSYN
  • BE2 - Parity Detect
  • BV2 - -5V (core)

Removed signals

Since grants could not be supported in the number of pins available in a dual connector, all grant pins were removed, along with some ground pins.

Pins

The pins which changed function from normal UNIBUS to MUD are listed below.

  • AB2 - Ground
  • AN1 - Ground
  • AP1 - Ground
  • AR1 - Ground
  • AS1 - Ground
  • AU1 - NPG
  • AV1 - BG7
  • AV2 - Ground
  • BA1 - BG6
  • BB1 - BG5
  • BB2 - Ground
  • BD1 - Ground
  • BE1 - Ground
  • BE2 - BG4
  • BV2 - Ground

See also

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