Difference between revisions of "Modified UNIBUS Device"

Revision as of 16:45, 22 July 2016

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 grant (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 threfore do not contain requests or grants (or other interrupt-related signals, such as INTR, SACK, etc); the pins were recycled for other functions.

Some contain a number of lines for communication between a parity controller, and parity-capable 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 conectors (needed for signals for interrupts or DMA, for devices which did those), with most UNIBUS signals present in both; the combination is sometimes called MUD/SPC.

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.

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 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.

Pinout

The pins which changed from standard UNIBUS to 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)

@@ Line 1: / Line 1: @@
 '''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 pins (in the [[DEC card form factor#Edge connector contact identification|A-B connectors]]) to carry UNIBUS signals (mostly pin-compatible with the usual dual UNIBUS slot).
+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 card form factor#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.
-There were a few differences with the UNIBUS dual connector. The most important was that 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 MUD pins do not contain grants.
+The most important was that 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]]), a full-function UNIBUS slot is not possible with only two connectors. The MUD connectors threfore do not contain requests or grants (or other interrupt-related signals, such as INTR, SACK, etc); the pins were recycled for other functions.
-The grant pins were recycled to contain a number of lines for communication between a parity controller, and parity-capable memory boards plugged into that backplane; and also additional voltages (primarily for core memory).
+Some contain a number of lines for communication between a parity controller, and parity-capable 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 conectors (needed for grants, for devices which did interrupts or DMA), with most UNIBUS signals present in both; the combination is  sometimes called MUD/SPC.
+Technically, a MUD slot only describes the A-B connectors; most backplanes also provided SPC functionality in the C-F conectors (needed for signals for interrupts or DMA, for devices which did those), with most UNIBUS signals present in both; the combination is sometimes called MUD/SPC.
-The [[dd11-c]] (4-slot0 and  [[DD11-D]] (9-slot) and later backplanes generally provided MUD slots, not the earlier SPC slots; however, generally the slots in these backplanes are MUD/SPC - other than the entrance and exit slots, which have normal two-slot UNIBUS in A-B.
+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.
 ==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,
+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 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.
@@ Line 23: / Line 23: @@
 The additional voltages were + and -15V, -5V, and +20V.
-==Pinout==
+===Pinout===
 The pins which changed from standard UNIBUS to MUD are:

Difference between revisions of "Modified UNIBUS Device"

Revision as of 16:45, 22 July 2016

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Added signals

Pinout

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