QBUS backplanes - Revision history

Jnc: /* External links */ Bitsavers has reorganized a bit

2026-10-07T23:57:04Z

External links: Bitsavers has reorganized a bit

← Older revision		Revision as of 23:57, 7 October 2026
Line 71:		Line 71:
	==External links==		==External links==

	* [http://www.bitsavers.org/pdf/dec/qbus/~~Digital_Microcomputer_Products_Handbook_1985~~.pdf Microcomputer Products Handbook (19850] - backplanes are covered in Part X, 'Backplanes, Enclosures, and Expansion Cables'		* [http://www.bitsavers.org/pdf/dec/qbus/EB-26078-41_Digital_Microcomputer_Products_Handbook_1985.pdf Microcomputer Products Handbook (19850] - backplanes are covered in Part X, 'Backplanes, Enclosures, and Expansion Cables'
	* [https://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/hardware/micronotes/numerical/micronote29.txt Q-bus Expansion Concepts] ([[MicroNote]] #029)		* [https://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/hardware/micronotes/numerical/micronote29.txt Q-bus Expansion Concepts] ([[MicroNote]] #029)
	* [http://www.douglaspcb.com/ Douglas Electronics] still sells extender cards for DEC backplanes		* [http://www.douglaspcb.com/ Douglas Electronics] still sells extender cards for DEC backplanes

Jnc: Clarify that not just aperipherls can go in QBUS slots

2024-08-26T16:57:43Z

Clarify that not just aperipherls can go in QBUS slots

← Older revision		Revision as of 16:57, 26 August 2024
Line 1:		Line 1:
	'''QBUS backplanes''' come mostly in two physical types, [[DEC card form factor\|dual-width]] and quad-width. In the quad-width [[backplane]]s, each slot held four 'connectors' (DEC's term for a group of [[DEC edge connector contact identification\|edge connector pins]]), denominated 'A'-'D'.		'''QBUS backplanes''' come mostly in two physical types, [[DEC card form factor\|dual-width]] and quad-width. In the quad-width [[backplane]]s, each slot held four 'connectors' (DEC's term for a group of [[DEC edge connector contact identification\|edge connector pins]]), denominated 'A'-'D'.

	The [[QBUS]] itself is fully carried in a dual slot, and the backplanes with quad slots are further sub-divided into two types, the so-called '''Q/Q''' and '''Q/CD'''. In quad Q/Q units, both sides (pairs of 'connectors') of each quad slot are fully wired for QBUS, and so a single slot can hold two separate dual-width QBUS [[peripheral controller\|~~devices~~]]. The device locations are usually arranged for [[bus grant line\|grant]] priority in so-called 'serpentine' order, i.e. one with the devices in the following order (facing the backplane from the board side):		The [[QBUS]] itself is fully carried in a dual slot, and the backplanes with quad slots are further sub-divided into two types, the so-called '''Q/Q''' and '''Q/CD'''. In quad Q/Q units, both sides (pairs of 'connectors') of each quad slot are fully wired for QBUS, and so a single slot can hold two separate dual-width QBUS [[peripheral controller\|device]], [[main memory\|memory]], etc [[printed circuit board\|cards]]. The device locations are usually arranged for [[bus grant line\|grant]] priority in so-called 'serpentine' order, i.e. one with the devices in the following order (facing the backplane from the board side):

	1-2<br>4-3<br>5-6<br>8-7<br>9-10		1-2<br>4-3<br>5-6<br>8-7<br>9-10

Jnc: Switch to standard wording; add link

2024-08-25T11:24:53Z

Switch to standard wording; add link

← Older revision		Revision as of 11:24, 25 August 2024
Line 1:		Line 1:
	'''QBUS backplanes''' come mostly in two physical types, [[DEC card form factor\|dual-width]] and quad-width. In the quad-width [[backplane]]s, each slot held four 'connectors' (~~denominated 'A'-'D'),~~ DEC's term for a [[DEC edge connector contact identification\|~~group of~~ edge connector pins]].		'''QBUS backplanes''' come mostly in two physical types, [[DEC card form factor\|dual-width]] and quad-width. In the quad-width [[backplane]]s, each slot held four 'connectors' (DEC's term for a group of [[DEC edge connector contact identification\|edge connector pins]]), denominated 'A'-'D'.

	The [[QBUS]] itself is fully carried in a dual slot, and the backplanes with quad slots are further sub-divided into two types, the so-called '''Q/Q''' and '''Q/CD'''. In quad Q/Q units, both sides of each quad slot are fully wired for QBUS, and so a single slot can hold two separate dual-width QBUS [[peripheral controller\|devices]]. The device locations are usually arranged for grant priority in so-called 'serpentine' order, i.e. one with the devices in the following order (facing the backplane from the board side):		The [[QBUS]] itself is fully carried in a dual slot, and the backplanes with quad slots are further sub-divided into two types, the so-called '''Q/Q''' and '''Q/CD'''. In quad Q/Q units, both sides (pairs of 'connectors') of each quad slot are fully wired for QBUS, and so a single slot can hold two separate dual-width QBUS [[peripheral controller\|devices]]. The device locations are usually arranged for [[bus grant line\|grant]] priority in so-called 'serpentine' order, i.e. one with the devices in the following order (facing the backplane from the board side):

	1-2<br>4-3<br>5-6<br>8-7<br>9-10		1-2<br>4-3<br>5-6<br>8-7<br>9-10

Vaxorcist: /* DEC backplanes */ H9274 VT103 backplane added

2024-08-17T07:11:22Z

DEC backplanes: H9274 VT103 backplane added

← Older revision		Revision as of 07:11, 17 August 2024
Line 29:		Line 29:
	\|-		\|-
	\| [[H9273 backplane\|H9273]] \|\| Q/CD \|\| 9 \|\| Q18 \|\| [[BA11-N mounting box\|BA11-N]] \|\| none		\| [[H9273 backplane\|H9273]] \|\| Q/CD \|\| 9 \|\| Q18 \|\| [[BA11-N mounting box\|BA11-N]] \|\| none
			\|-
			\| [[H9274 backplane\|H9274]] \|\| Q/Q \|\| 4 \|\| Q18 \|\| [[VT103\|VT103]] \|\| none \|\| special connectors for use in the VT103
	\|-		\|-
	\| H9275 \|\| Q/Q \|\| 9 \|\| Q22 \|\|  \|\| 120 ohms		\| H9275 \|\| Q/Q \|\| 9 \|\| Q22 \|\|  \|\| 120 ohms

Jnc: Minor clarity improvements

2024-07-30T14:29:20Z

Minor clarity improvements

← Older revision		Revision as of 14:29, 30 July 2024
Line 1:		Line 1:
	'''QBUS backplanes''' come ~~mainly~~ in two physical types, [[DEC card form factor\|dual-width]] and quad-width. In the quad-width [[backplane]]s, each slot held four 'connectors', DEC's term for a [[DEC edge connector contact identification\|group of edge connector pins]]~~, denominated 'A'-'D'~~.		'''QBUS backplanes''' come mostly in two physical types, [[DEC card form factor\|dual-width]] and quad-width. In the quad-width [[backplane]]s, each slot held four 'connectors' (denominated 'A'-'D'), DEC's term for a [[DEC edge connector contact identification\|group of edge connector pins]].

	The [[QBUS]] itself is fully carried in a dual slot, and the ~~quads~~ are further sub-divided into two types, the so-called '''Q/Q''' and '''Q/CD'''. In quad Q/Q units, both sides of each quad slot are fully wired for QBUS, and so a single slot can hold two separate dual-width QBUS [[peripheral controller\|devices]]. The device locations are usually arranged for grant priority in so-called 'serpentine' order, i.e. one with the devices in the following ~~kind of~~ order (facing the backplane from the board side):		The [[QBUS]] itself is fully carried in a dual slot, and the backplanes with quad slots are further sub-divided into two types, the so-called '''Q/Q''' and '''Q/CD'''. In quad Q/Q units, both sides of each quad slot are fully wired for QBUS, and so a single slot can hold two separate dual-width QBUS [[peripheral controller\|devices]]. The device locations are usually arranged for grant priority in so-called 'serpentine' order, i.e. one with the devices in the following order (facing the backplane from the board side):

	1-2<br>4-3<br>5-6<br>8-7<br>9-10		1-2<br>4-3<br>5-6<br>8-7<br>9-10
Line 9:		Line 9:
	In a quad Q/CD backplane, the [[DEC edge connector contact identification\|CD connectors]] form a private bus, sometimes called the [[CD interconnect]], used to connect together board pairs. (The CD connectors run down the right-hand side, when facing the side of the backplane where the boards plug in, with the CPU at the top.)		In a quad Q/CD backplane, the [[DEC edge connector contact identification\|CD connectors]] form a private bus, sometimes called the [[CD interconnect]], used to connect together board pairs. (The CD connectors run down the right-hand side, when facing the side of the backplane where the boards plug in, with the CPU at the top.)

	It is usually possible to upgrade 18-bit backplanes to 22-bit; see [[Upgrading QBUS backplanes]].		It is usually possible to upgrade [[QBUS#Variable address size\|18-bit QBUS]] backplanes to 22-bit; see [[Upgrading QBUS backplanes]].

	'''''NOTE WELL:''''' For reasons which seem utterly incomprehensible, many boards designed for Q/CD slots (such as [[Private Memory Interconnect\|PMI]] cards) '''do not''' avoid the QBUS pins on the CD connectors which contain 'hazardous' (to TTL circuitry) voltages. [''NOTE:'' The exact failure mode here is still not understood; the PMI spec was examined, but no clash of pin assignments was found. The warning is accurate, though: [https://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/hardware/micronotes/numerical/micronote28.txt MicroNote #28] says "MSV11-J MODULES CAN[NOT] BE PLACED IN A Q/Q BACKPLANE SLOT. IF THIS IS ATTEMPTED PERMANENT DAMAGE WILL BE DONE TO THE BOARDS".] So, plugging such a card into a Q/Q backplane will generally '''''destroy''''' the card.		'''''NOTE WELL:''''' For reasons which seem utterly incomprehensible, many boards designed for Q/CD slots (such as [[Private Memory Interconnect\|PMI]] cards) '''do not''' avoid the QBUS pins on the CD connectors which contain 'hazardous' (to TTL circuitry) voltages. [''NOTE:'' The exact failure mode here is still not understood; the PMI spec was examined, but no clash of pin assignments was found. The warning is accurate, though: [https://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/hardware/micronotes/numerical/micronote28.txt MicroNote #28] says "MSV11-J MODULES CAN[NOT] BE PLACED IN A Q/Q BACKPLANE SLOT. IF THIS IS ATTEMPTED PERMANENT DAMAGE WILL BE DONE TO THE BOARDS".] So, plugging such a card into a Q/Q backplane will generally '''''destroy''''' the card.
Line 15:		Line 15:
	==Backplane types==		==Backplane types==

	Several manufacturers produced ~~QBus~~ compatible backplanes:		Several manufacturers produced QBUS compatible backplanes:

	===DEC ~~Backplanes~~===		===DEC backplanes===

	The following table lists the backplanes produced by [[Digital Equipment Corporation\|DEC]]:		The following table lists the backplanes produced by [[Digital Equipment Corporation\|DEC]]:
Line 49:		Line 49:
	The DDV11-C details are somewhat speculative; in the [[VS11 Graphic System\|VS11]], it is used with a [[VSV11 Graphic System\|VSV11]], and the VSV11's Video Bus is carried over the E-F connectors. Puzzlingly, the VS11 documentation shows that a DDV11-D may also be used - but it claims to have the E-F connectors un-wired.		The DDV11-C details are somewhat speculative; in the [[VS11 Graphic System\|VS11]], it is used with a [[VSV11 Graphic System\|VSV11]], and the VSV11's Video Bus is carried over the E-F connectors. Puzzlingly, the VS11 documentation shows that a DDV11-D may also be used - but it claims to have the E-F connectors un-wired.

	===MDB ~~Backplanes~~===		===MDB backplanes===

	[[MDB Systems]] produced many third-party ~~QBus~~ options, including backplanes and complete chassis systems:		[[MDB Systems]] produced many third-party QBUS options, including backplanes and complete chassis systems:

	{\| class="wikitable"		{\| class="wikitable"
	! ID !! Type !! ~~Width~~ \|\| Address Width !! Assembly \|\| Chassis !! Termination \|\| Comments		! ID !! Type !! # Slots \|\| Address Width !! Assembly \|\| Chassis !! Termination \|\| Comments
	\|-		\|-
	\| [[40328]] \|\| Q/Q \|\| 8 \|\| Q18 \|\| [[MLSI-BPA84]] \|\| [[MLSI-BA11-200]] \|\| none \|\| Wire wrap pins, can be wrapped to Q22		\| [[40328]] \|\| Q/Q \|\| 8 \|\| Q18 \|\| [[MLSI-BPA84]] \|\| [[MLSI-BA11-200]] \|\| none \|\| Wire wrap pins, can be wrapped to Q22
	\|}		\|}

	'Type' indicates slot height and wiring, a value with a slash indicates quad height slots. ~~'Width' is the number of slots;~~ if the backplane is quad-height, twice as many dual-height modules will fit.		'Type' indicates slot height and wiring, a value with a slash indicates quad height slots. <!-- if the backplane is quad-height, twice as many dual-height modules will fit. - removed as duplicative of the note under the table above -->

	As with DEC backplanes, MDB backplanes that are Q/Q will damage ~~QBus~~ cards with CD interconnects.		As with DEC backplanes, MDB backplanes that are Q/Q will damage QBUS cards with CD interconnects.

	==Further reading==		==Further reading==

Jnc: /* DEC Backplanes */ Change column title to '# slots'

2024-07-30T01:33:21Z

DEC Backplanes: Change column title to '# slots'

← Older revision		Revision as of 01:33, 30 July 2024
Line 22:		Line 22:

	{\| class="wikitable"		{\| class="wikitable"
	! ID !! Type !! ~~Height~~ \|\| Address Width !! Chassis !! Termination \|\| Comments		! ID !! Type !! # Slots \|\| Address Width !! Chassis !! Termination \|\| Comments
	\|-		\|-
	\| [[H9270 backplane\|H9270-A]] \|\| Q/Q \|\| 4 \|\| Q18 \|\| [[BA11-M mounting box\|BA11-M]] \|\| none		\| [[H9270 backplane\|H9270-A]] \|\| Q/Q \|\| 4 \|\| Q18 \|\| [[BA11-M mounting box\|BA11-M]] \|\| none
Line 45:		Line 45:
	\|}		\|}

	'Type' indicates whether it is dual-width ('Q') or quad. '~~Height~~' is the number of slots; the number of dual-width board which can be plugged in is twice this~~, for Q/Q quad backplanes~~.		'Type' indicates whether it is dual-width ('Q') or quad. '# slots' is the number of slots; for Q/Q quad backplanes, the number of dual-width board which can be plugged in is twice this.

	The DDV11-C details are somewhat speculative; in the [[VS11 Graphic System\|VS11]], it is used with a [[VSV11 Graphic System\|VSV11]], and the VSV11's Video Bus is carried over the E-F connectors. Puzzlingly, the VS11 documentation shows that a DDV11-D may also be used - but it claims to have the E-F connectors un-wired.		The DDV11-C details are somewhat speculative; in the [[VS11 Graphic System\|VS11]], it is used with a [[VSV11 Graphic System\|VSV11]], and the VSV11's Video Bus is carried over the E-F connectors. Puzzlingly, the VS11 documentation shows that a DDV11-D may also be used - but it claims to have the E-F connectors un-wired.

Jnc: /* Further reading */ +Micro Backplane Mechanical Mounting Guidelines

2024-07-27T16:45:27Z

Further reading: +Micro Backplane Mechanical Mounting Guidelines

← Older revision		Revision as of 16:45, 27 July 2024
Line 62:		Line 62:

	As with DEC backplanes, MDB backplanes that are Q/Q will damage QBus cards with CD interconnects.		As with DEC backplanes, MDB backplanes that are Q/Q will damage QBus cards with CD interconnects.

			==Further reading==

			* ''Micro Backplane Mechanical Mounting Guidelines'', [[MicroNote]] #026

	==External links==		==External links==

Glitch: /* MDB Backplanes */

2024-07-24T18:33:44Z

MDB Backplanes

← Older revision		Revision as of 18:33, 24 July 2024
Line 56:		Line 56:
	! ID !! Type !! Width \|\| Address Width !! Assembly \|\| Chassis !! Termination \|\| Comments		! ID !! Type !! Width \|\| Address Width !! Assembly \|\| Chassis !! Termination \|\| Comments
	\|-		\|-
	\| [[40328]] \|\| Q/Q \|\| 8 \|\| Q18 \|\| [[MLSI--BPA84]] \|\| [[MLSI-BA11-200]] \|\| none \|\| Wire wrap pins, can be wrapped to Q22		\| [[40328]] \|\| Q/Q \|\| 8 \|\| Q18 \|\| [[MLSI-BPA84]] \|\| [[MLSI-BA11-200]] \|\| none \|\| Wire wrap pins, can be wrapped to Q22
	\|}		\|}

Glitch: /* MDB Backplanes */

2024-07-24T18:33:36Z

MDB Backplanes

← Older revision		Revision as of 18:33, 24 July 2024
Line 54:		Line 54:

	{\| class="wikitable"		{\| class="wikitable"
	! ID !! Type !! Width \|\| Address Width !! Chassis !! Termination \|\| Comments		! ID !! Type !! Width \|\| Address Width !! Assembly \|\| Chassis !! Termination \|\| Comments
	\|-		\|-
	\| [[40328]] \|\| Q/Q \|\| 8 \|\| Q18 \|\| [[MLSI-BA11-200]] \|\| none \|\| Wire wrap pins, can be wrapped to Q22~~, MLSI BPA-84 when mounted in a card cage~~		\| [[40328]] \|\| Q/Q \|\| 8 \|\| Q18 \|\| [[MLSI--BPA84]] \|\| [[MLSI-BA11-200]] \|\| none \|\| Wire wrap pins, can be wrapped to Q22
	\|}		\|}

Glitch: /* MDB Backplanes */

2024-07-24T18:32:13Z

MDB Backplanes

← Older revision		Revision as of 18:32, 24 July 2024
Line 56:		Line 56:
	! ID !! Type !! Width \|\| Address Width !! Chassis !! Termination \|\| Comments		! ID !! Type !! Width \|\| Address Width !! Chassis !! Termination \|\| Comments
	\|-		\|-
	\| [[40328]] \|\| Q/Q \|\| 8 \|\| Q18 \|\| [[MLSI-BA11-200]] \|\| none \|\| Wire wrap pins, can be wrapped to Q22		\| [[40328]] \|\| Q/Q \|\| 8 \|\| Q18 \|\| [[MLSI-BA11-200]] \|\| none \|\| Wire wrap pins, can be wrapped to Q22, MLSI BPA-84 when mounted in a card cage
	\|}		\|}