Fitting it to a backplane

Which slot

UNIBUS · UniBone

A standard quad SPC slot, with the NPG grant chain open at CA1–CB1. If you are emulating an RL11, the tidiest thing is to pull the existing RL11 and put UniBone in its place.

QBUS · QBone

Any quad QBUS slot. Close every empty QBUS slot between the processor and the last used slot with G9047 grant continuity cards — and note that not all slots are QBUS slots and the slot order is not always obvious. See Backplane geometry below.

Watch for shorts

The BeagleBone is a little fat, and some of its parts can touch the solder side of a module sitting above it. Either slip thin card between the modules, or mount the card below an empty slot filled with a grant continuity card.

Terminators

Single-backplane systems do not need a terminator pack at the bus end — DEC processors terminate the bus themselves. Multi-backplane systems involve some alchemy about where to add terminators and whether to use 120 Ω or 240 Ω at the far end; some backplanes have resistor packs soldered on already.

The card carries no onboard terminators. If it is replacing the processor — for a self test, say — you need terminator packs.

Jumpers

QBUS · QBone

Address width

QBUS runs 16, 18 or 22 bits, and the processor decides which. QBone cannot infer it from bus traffic, so two things must be set:

• On an LSI-11/03, remove the DAL<21:18> jumpers — those backplane lines carry CPU-internal signals there.
• Tell the software the width, so it knows how much memory to emulate and for which addresses to assert the BS7 I/O-page signal.

Which processor implies which width: the LSI-11 M7264 and 11/2 are 16-bit; the 11/23 with an F-11 is 18-bit; the 11/23+ and the J11-based 11/53, /73 and /93 are 22-bit.

C/D grant continuity

Interrupt and DMA grant signals daisy-chain from slot to slot. Fit the CD GRANT jumpers if the card’s C/D fingers land in a socket carrying a standard QBUS:

Backplane	Card position	CD GRANT jumpers
H9270	any slot	closed
H9275	any slot	closed
H9276	any slot	open
H9278	slots 1–3	open
H9278	slots 4–8	closed

Get this wrong and controllers plugged behind the card will fail on interrupts or DMA.

50 Hz on EVNT

DEC power supplies put a 50/60 Hz square wave on the EVNT line. On another power option, close the EVNT 50Hz jumper to have the card generate it.

Test and factory jumpers

The IRQ/DMA GRANT block can disconnect IAKI/IAKO/DMGI/DMGO from the card or short them for self test. EEPROM ADDR selects the cape EEPROM address. Leave both in their factory positions.

Backplane geometry

QBUS · QBone

All QBUS backplanes carry the bus on rows A and B. What varies is C and D: sometimes more QBUS, sometimes a separate bus, sometimes a separate bus with daisy-chain logic.

There is one rule to remember: if the card’s C/D fingers go into a QBUS slot rather than a special C/D slot, set the grant continuity jumpers JP7 and JP8.

Backplanes also differ in slot ordering — the “zig-zag” — and in how many special C/D slots they have. The QBUS information page is the reference worth having open.

Which lines the backplane must carry

The backplane has to carry the address lines in use between processor and memory or I/O device. As far as is known every backplane is at least 18-bit capable, so DAL<17:0> is always wired. The H9270 can be modified to carry DAL<21:18> as well, which lets a 4 MB machine run in that handsome 4×4 cage; several web pages describe how.

Then, per device class:

• Passive device (memory or register): must respond only to the address lines in use, and ignore the unused upper ones.
• Active DMA device: must generate a proper BS7 for I/O-page addresses.

Some cards have their own width jumper — an RLV12 does. Others are limited: a DRV11-B M7950 has only 16 address lines.

The line-time clock

QBUS · QBone

QBUS EVNT causes an unconditional processor trap, and is normally used for the line-time clock. It can be produced by the power supply, by a peripheral like a BDV11 M8012 (which switches it under program control), or by the card’s own 50 Hz source via jumper JP9.

Only one source may drive it.

Whether the processor uses it is a separate tangle. Some cabinets tie EVNT to ground through an AUX ON/OFF front-panel switch (BA-23S, 11/23) — on others that switch is main power. Some processors disable the trap by wire-wrap jumper (LSI-11, 11/23); some by software register (11/23+, J11); on a KDJ11-E the presence of that register is itself configurable, and it combines with a hardware jumper.

Whether you need it depends on the guest:

• Unixes need it and will not boot without it.
• RSX-11M and M+ need it for task scheduling.
• RT-11 wants it only for the time of day.
• If EVNT is enabled and the processor takes the trap, the system needs a handler at vector 100 or it will crash.

UNIBUS · UniBone

UNIBUS has no EVNT line. The line-time clock is a KW11-L, which QUniLator can emulate.

Then

With the card seated and jumpered, go to Installing the software, or to the acceptance test if the card is new to you.