Question about QBUS wiring

[jplr]

Hi all,

I am considering building my own QBus Q/Q with wire-wrap for LSI-11 cards, because finding an existing one is difficult and costly.
For connectors it looks to me that Vector R600 edge connectors or similar fit the cards' connectors.
I read too quickly the chapter 6 of the LSI-11 bus specification.

Do I understand correctly that most lines are multiplexed on all slots, for example:
- A given BDAL line in one slot is electrically connected to the same BDAL line in other slots.
- Same for the control signals such as BSYNC, BDIN, BDOUT,.
- Same for electric power lines where there are special signals such as Binit, BDCOK, RTC and power OK.
An exception is the bus control signals (TDMR, TSACK, etc) which are connected in round robin.
Another exception is the interrupt lines with one interrupt line is affected to only one card.
All multiplexed lines should be terminated by a 120 ohms resistance.

If possible I would like to address 32Kb or even 48Kb, what must I know?

What precautions for mitigating cross-talk between wires and minimizing capacitances on lines?

Thanks for your answers!

Jean-Pierre

 

[pbirkel@gmail.com]

The attached DATARAM document includes a Qbus pin-level wiring diagram on the right side of page 17 (of 20) along with other useful information. Older Unibus backplanes ("system units") used point-to-point standard wire wrap techniques, excepting in a few cases of timing/noise sensitive lines in the 11/70 (and possibly the 11/45-50-55) which used a twisted pair of wires with the second grounded at both ends, but those were all long runs (many tens of cm).

 

[jplr]

The attached DATARAM document includes a Qbus pin-level wiring diagram on the right side of page 17 (of 20) along with other useful information. Older Unibus backplanes ("system units") used point-to-point standard wire wrap techniques, excepting in a few cases of timing/noise sensitive lines in the 11/70 (and possibly the 11/45-50-55) which used a twisted pair of wires with the second grounded at both ends, but those were all long runs (many tens of cm).

That document is an incredible resource!
Many thanks for your quick answer!
Jean-Pierre

 

[ftcnet]

For connectors it looks to me that Vector R600 edge connectors or similar fit the cards' connectors.

Also see the discussion at: https://forum.vcfed.org/index.php?t...c-flip-chip-edge-connectors.78927/#post966704
The ECS connectors are probably the closest to what you want for wire-wrap use. They're 'straight row' instead of the 'staggered row' style that DEC used.

 

[Teletech]

Not to be a spoilsport, but if you want more than a couple slots then the cost of connectors is likely to be greater than the cost for a backplane out of a BA23, or indeed, an entire BA23, and that's not even considering your time as having any value.
Try putting a WTB add up and see if someone can help out. I'd offer, but I suspect shipping from the UK will be a lot more reasonable.

 

[g4ugm]

Not to be a spoilsport, but if you want more than a couple slots then the cost of connectors is likely to be greater than the cost for a backplane out of a BA23, or indeed, an entire BA23, and that's not even considering your time as having any value.
Try putting a WTB add up and see if someone can help out. I'd offer, but I suspect shipping from the UK will be a lot more reasonable.

I looked long and hard for LSI/11 backplanes in the UK and never found one at a reasonable price. I have quite a few cards, but a backplane is hard to find. The only one I have is I think a Q18 so another level of pain to fix for later 11's..

 

[jplr]

What do you think about those two projects which are about modern Qbus designs:
- https://github.com/GeorgeRudolf/Q22Mini
- https://github.com/joelang/pdp-panel
I tried Rudolf's files on the online toolset of a PCB maker (Seeed) and it was able to find all needed information to produce a PCB.
That said, I didn't buy anything, wait and see.

 

[g4ugm]

What do you think about those two projects which are about modern Qbus designs:
- https://github.com/GeorgeRudolf/Q22Mini
- https://github.com/joelang/pdp-panel
I tried Rudolf's files on the online toolset of a PCB maker (Seeed) and it was able to find all needed information to produce a PCB.
That said, I didn't buy anything, wait and see.

Looks good, if you only have narrow cards. Be interesting to see if any one makes one...

 

[jplr]

As for connectors I tried to insert a two slots memory card in a Vector R 681-1 wirewrap connector (I can't on my M7264 as my only connector does not fit the four slots card).
Yet I agree that it's difficult to center the connector, and that it does not cover more than 40% of a pin of the card edge connector.
For purists it's certainly awful, yet I am sure the electrical contacts are good.
And on Aliexpress there are low cost versions of this connector.

 

[gslick]

Douglas Electronics Inc.
72-125C-EL
DEC compatible - 72 pins of .025" square, .620" length
https://www.douglaspcb.com/index.php/72-125c-el.html

 

[jplr]

Thanks for the link @gslick!

Yet I think it would better fit the need of someone in the USA and possibly Canada.
Indeed I asked for a quote for my town in France, and got shipping costs at $44.84.
A Eurozone solution better fits my needs and in addition in this case there is no custom taxes (~20%).

Anyway, thanks again @gslick for taking the time to write this, it was helpful.

 

[gslick]

I looked long and hard for LSI/11 backplanes in the UK and never found one at a reasonable price. I have quite a few cards, but a backplane is hard to find. The only one I have is I think a Q18 so another level of pain to fix for later 11's..

In the US currently you could get an H9278-A backplane from a BA23 at a somewhat reasonable price:

https://www.ebay.com/itm/325510697654

The last one the same seller listed sold for US $64, plus shipping:

https://www.ebay.com/itm/325499350324

Sorry that doesn't help if you're somewhere in Europe.

 

[g4ugm]

In the US currently you could get an H9278-A backplane from a BA23 at a somewhat reasonable price:

https://www.ebay.com/itm/325510697654

The last one the same seller listed sold for US $64, plus shipping:

https://www.ebay.com/itm/325499350324

Sorry that doesn't help if you're somewhere in Europe.

Yes, both me and the original poster are in Europe. At least he is in the EU so have lots more options tax and duty free.