RE: [N8VEM-S100:1394] S-100 Bus Terminator

Hi Jack! Thanks! I am sure we can design a modification to the S-100 bus extender board to include the bus terminator. My concern is messing up the bus extender design by introducing the bus termination circuitry. It does make some sense though to roll the bus terminator into the bus extender rather than make a new separate board.

I’d like to hear more about what John has to say on the idea. One hitch I see is that the bus extender board is not IEEE-696 form factor compatible and would interfere with closing an S-100 chassis.

Thanks and have a nice day!

Andrew Lynch

From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Jack Rubin
Sent: Sunday, February 10, 2013 12:59 PM
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:1394] S-100 Bus Terminator

I’ve always liked the EXTERMINATOR, for the name if nothing else, but I’m not sure that combining termination with an extension card is useful. I tend to want to use an extender that won’t disturb the existing system which may or may not already have termination, and if termination is needed, then I wouldn’t want to sacrifice an extension card to provide it. I’d rather see a short board which simply provides termination in the minimal amount of space required. The CompuPro active terminator is only about 3 inches high.

Jack

From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Paul Birkel
Sent: Sunday, February 10, 2013 2:38 AM
To: n8vem...@googlegroups.com
Subject: Re: [N8VEM-S100:1375] S-100 Bus Terminator

Andrew:

Being a congenital penny-pincher, as well as a "tweaker", it strikes me as a lost opportunity to define a PCB like this with *lots* of unused space (and yet sucking up a full S-100 slot). At a minimum, how about filling the remaining space with a through-hole proto-area array? It would/could be accompanied by appropriate regulators along one edge but the setup/layout would be spatially similar to the buffered proto-board (replacing the buffer-area with the line-clamp area). This would leave opportunities for experimenters (with legacy S-100 backplanes) to wire-up small accessory circuits -- else no impact on the termination function?

Alternatively, place the bus-terminator circuitry onto the unused area of the bus-extender card and get three-in-one functionality with extension, termination, and probe functions. An example of this approach of combining termination and extension was the VTE100a "EXTERMINATOR"; see:

http://maben.homeip.net/static/S100/vamp/cards/VMP%20VTE%20100-A%20Terminator.pdf
http://maben.homeip.net/static/S100/vamp/photos/VAMP%20VTE-100%20Exterminator.jpg
http://maben.homeip.net/static/S100/vamp/photos/VTE%20100a%20Exterminator.gif

If trying to go 3-in-1 ends up running into real estate issues then just combine termination & extension like the VAMP.

Another possibility would be to commit all/part of the (above) proposed proto-area to specific generally-useful functions. Two possibilities would be a configurable basic UART serial I/O port and/or a configurable 8 or 16-bit (E)EPROM handling up to 1 MB chips. I believe that someone pointed out recently that it would be useful to have a board with these sorts of basic functions in order "bring-up" legacy CPU PCBs in a minimal configuration. One could possibly swap one of these options for the probe in a 3-in-1 configuration? Unfortunately it seems to me that when including the extension-function that the resulting routing problems when adding something like I/O or ROM might require a lot of accessory over-board wires to effectively provide a (minimal) third connection-plane. So that might not be a good idea. But the VAMP illustrates that termination+extension go together quite well.

My preference would be to leave the existing probe+extension PCB alone, and instead look towards combining termination, Serial I/O, and (E)EPROM into a single card. This plus legacy CPU and RAM cards would result in a functional system on any "naked backplane". If some RAM could be squeezed into this multi-purpose board, so much the better :->. We have all of these circuits in tested-form, the only issue would seem to be routing. This sort of board would also be useful to a wider audience who could only populate the subsections of immediate need (e.g., not actually use the termination section if employing a self-terminated backplane) -- and this would increase the board-orders and therefore the likelihood that we'll quickly reach a good ROI threshold.

The bottom line for me is that a pure termination PCB seems like a lost opportunity. And might not easily reach critical-mass for a board-order :-<.

On Sat, Feb 9, 2013 at 9:19 PM, Andrew Lynch <LYN...@yahoo.com> wrote:

Attached are the schematic and PCB layout files for the S-100 Bus Terminator.

Please review and send any changes and/or corrections to me.

Thanks and have a nice day!

Andrew Lynch

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