Serial UNIBUS Repeater?

Paul Anderson useddec at
Mon Jun 15 11:06:23 CDT 2015

Hi Mark,

Do you just need a 4 or 9 slot backplane?

I Don't see the need for a repeater unless I'm missing something.


On Mon, Jun 15, 2015 at 10:57 AM, Mark J. Blair <nf6x at> wrote:

> Has anybody ever made a UNIBUS repeater with a high speed serial link
> between the bus segments yet? I'm curious because my VAX-11/730 backplane
> is full, and it would be nice to be able to experiment with additional
> hardware without needing to pull out one of the existing boards, i.e.,
> adding a TK50 interface without removing the DEUNA, adding a SCSI card to
> boot from a scsi2sd without pulling the integrated drive controller, etc.
> There's a blank spot in the TU80 cabinet that looks like it may be tall
> enough for an expansion chassis, but the thought of adding more big ribbon
> cables to the belly plate area and then routing them between racks doesn't
> appeal to me. Running something like a CAT5 cable between the two racks
> would be a lot easier. Another application would be for placing a small
> remote UNIBUS backplane on the test bench for easy access, and cabling it
> to a VAX or PDP-11 elsewhere in the room.
> This should be quite possible with modern hardware, but I'm curious about
> whether something similar has been done before.
> --
> Mark J. Blair, NF6X <nf6x at>

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