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June 1998

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Subject:
From:
Jerry Cupples <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 30 Jun 1998 09:15:56 -0500
Content-Type:
text/plain
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text/plain (61 lines)
Colin Weber asked:

>We have a requirement to re-design an existing ISA bus card design onto a
>5V, 32-bit PCI card.
>
>1.
>First glance at PCI specifications highlight that there are two default
>sizes for these cards, Short and Long. What is the reasoning behind this?

There are many types of card cage configurations in PC's and some of them
have slots which can only accomodate a half length format. The PCI local
bus Specification rev 2.1 says "The fixed and variable height short length
cards were chosen for panel optimization to provide the lowest cost for a
function". I'd say the PC people have gotten wise to the idea that they
should get a smaller board for less money, and that the number and size of
components necessary to make an ethernet NIC, for instance, has dropped to
12-15 square inches. In short, cost.

>Or another way of asking the same question, can the length of the board be
>vary?

Yes. The length has a lower limit of about 12 cm from the faceplate edge to
the end of the finger connector. I have seen boards which have irregular
shapes in which the connector edge is a couple inches longer than the
opposite edge, and they are panelized to yield more units.

>Does it have to conform to either of the specific short or long lengths?

Our Company is definitely producing NIC's (network interface cards) shorter
than the 6.875" "short card", and so are many others. I'd recommend that
you go out and buy some products and take a look at the configurations.
Your local CompUSA should have numerous brands to choose from. I know that
Intel (who is godfather of the PCI bus) has some NIC's with very clever
small and irregular layouts. Both lenght and height are varied in many of
these.

See:
http://www.pcisig.com/


good luck,



Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com

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