Fun for the EE guys (board design)

Scott Quinn compoobah at
Sun Jun 11 19:32:32 CDT 2006

>> This board is plugged into the two connectors of the last memory board
>>in the chain. The cables are then connected to the terminator instead
>>of the board itself.

>Huh?  Perhaps you mean that the way the board connects to
>the rest of the machine is *through* the cables (i.e. there
>is not some other set of connectors on the board that plug
>into a "backplane")?  So, *normally* the cables plug into the
>memory board but, on the last board, the terminator sits
>"between" the cables and the board?

>In other words, any solution *must* have 4 connectors on it
>(you can't just take two INDIVIDUAL connectors and solder
>the RPAK's onto the back of those connectors (i.e. skip the
>PCB entirely!)

I think that I could probably get away without putting on the pass-through. My IM2 cable has 4 extra positions (IP2 + 1 IM2 are boards installed)
I think it unlikely that I will come across enough boards to where I would need the pass-through (would need a FPA + 3 extra IM2s).

I (not being an EE) wasn't sure about the seriousness of the crosstalk/unwanted reactance problem on computer busses. The downside to soldering
directly onto cables is that there is a separate power feed for the voltage divider network that must be accounted for. Wire-wrap holds distinct possibilities, though.

While I'm messing around with this, does anyone else have an IRIS 3k sans terminators?

Scott Quinn

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