11 Jun
2006
11 Jun
'06
5:20 p.m.
Scott Quinn wrote:
Found a problem in my IRIS 3k - didn't have a
terminator on the IM1 memory bus. I doubt that this is still available through
retail channels
Gerhard helped quite a lot by taking pictures of the board and giving a description of
where it went, now I need to fab one.
The board looks to be 4-layer (front&back traces with power and ground planes), which
is a bit difficult to do at home. This runs
in a 16MHz 68k system. Would it be possible to fab it using a barely-etched dual sided
board for power/ground planes and running
point-to-point wires for the signals, or is this asking for trouble as far as timing
issues go?
Termination is standard 331/331 resistors.
How large is it? You can probably get it done "for free" using one of
the "$500 promotions" that PCB manufacturers often have. Of course,
they are expecting you to SAVE $500 on your > $500 order... but, if
you are only doing one or two and can live without things like
silkscreen, you can probably send them a layout tweeked to come
in UNDER that $500 number (ie. FREE)
Otherwise...
What sort of connector does it have on it (sorry, I don't have an
IRIS)? I suspect you can probably hand-wire the whole thing
(depends on what they used to drive the bus and how sharp the
edges are). That's not a particularly fast bus (I've wirewarpped
68K designs that fast, easily).
--don