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Date:	Thu, 13 Sep 2007 01:03:52 -0700
From:	Ray Davison <raydav@charter.net >
Reply-To:	scoug-help@scoug.com
To:	scoug-help@scoug.com
Subject:	SCOUG-Help: Second Floppy Drive...?

Content Type: text/plain

Steven Levine wrote:
>
> The chipset probably handles 2 diskettes just fine, as does the BIOS.
> What's probably missing are the traces to connect the chipset to the
> connector. As Ray will tell you laying out complex boards with lots of
> interconnects is hard. Fewer traces makes it easier. There's also the
> costs savings of less copper and gold per board. It's not much for one
> board, but when you are working in the millions the difference is
> significant.

I have an alternate possibility. First, let's assume we have done
everything possible and the system in question really does not have B
support. I have seen that with this family of BIOS.

MBs have gotten smaller. That allowed the case to get smaller. That
made the front panel crowded. At the same time the world is drifting
away from floppies. So they drop B. And to make everything consistent
they took B out of BIOS setup. I think on this unit they missed that
last step.

There could be more savings than copper. A and B do not share all the
same lines on the bus. By dropping B they could also drop the line
drivers that were unique to B.

In recent times gold has only been used on contact fingers that were
etched onto the board. PCs don't have that type of connectors.

Trivia: The first printed wiring boards I worked on had all circuit
traces gold plated. The gold first served as an etch resist and then as
a corrosion resist. Some assemblers would drag a soldering iron over
every trace solder coating them, making them less resistant to
corrosion. This was before solder mask.

Ray

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