On Wed, 17 Jan 2007 11:46:36 -0000, "Philip"
<philip@NOSPAM.gn.apc.org> wrote:

<snip>

>I have just bought a new PC which only takes "half-height" PCI cards
>(although the so-called "specification" doesn't actually tell you this). I
>am pretty sure that my standard-height, short PCI card won't fit. But apart
>from the back-plate, the actual card itself if much lower than the full
>height - about 67mm including edge slots.


> But, my question is, what sort of standard is it? What are the
>standard dimensions of a "half-height" or "low-profile" PCI card, and will
>my card fit if I remove the back plate?


When buying a ready-made system, one cannot presume the
system adheres to standards rather than somewhat
proprietary. Even so, there is still the reasonable
presumption it has to adhere to some of them just to make
(their) sourcing of parts cost effective, instead of having
to reinvent everything at significantly higher cost in
design and manufacturing (parts the OEM buys then uses).

The length can vary quite a bit depending on how the board
is laid out, situated in the case, but a useful working
number is about 120mm length of PCB from the forward edge of
the PCI slot, to rearward edge that screws to the mounting
bracket. In other words there can't be anything blocking
the forward edge of the card when it doesn't extend forward
past the slot itself.

The height could be exceeded a few millimeters depending on
the design of the case, but another working number (I don't
recall if this is a spec # or not) for total PCB height
(including card edge) would be 65mm.

As to whether your card will fit if you remove the
backplate, how will you then mount it? It's easier to find
cards 65mm or less than to also find them with the back
mounting bracket, though I suppose you can machine down that
bracket to the height you need, or fabricate one though
often cards with so little on them that they'll fit on a
half height card, aren't very expensive if you had to find
an alternative with the shorter bracket included.

Some cards are shorter merely to save on cost of the PCB
material used, not necessarily targeted to fit a half height
standard, so you may find cards not much taller than 65mm
but still too tall to fit (like Promise Ultra/FastTrack 66
(not that you'd want to use one today but it's just an
example, a few years ago I ended up replacing the right
angle pin headers on a FastTrack66 with straight 180' header
and sawing off about 1 cm from a card so it would fit in a
low profile case... so it is possible to /make/ a card fit
sometimes, but more often the designer routed something up
nearer the top edge that can't be cut off)).