[asterisk-users] Question about PCI Slots for DIGIUMs Boards

[Nick Seraphin]

On Sat, 29 Mar 2008, Al Baker wrote:

> Detailed specs for the "types" of PCI slots on the system were posted 
> each and every time I posted int the line

Actually, your description wasn't 100% clear at all.

> _PCI Express_*: _two x8 slots*_, _two x8 low profile slots*_; *_PCI-X: 
> 64-bit/100MHz_* "

1)  This description seems to IMPLY that there are 5 slots total.  Do you
know if this is in fact correct?  It implies there are 2 PCI-E x8 slots, 2
PCI-E x8 low profile slots, and 1 PCI-X slot.  I wouldn't rely on that
however without talking to the vendor.

2) The first "PCI Express:" heading would normally imply that the slots
listed afterwards are ALL PCI Express slots, however PCI-X is not PCI
Express, so the vendor's description is confusing and misleading.

3) All these damn *'s you keep inserting, are those all done by you, or
are some of them from the web page description?  Most of the time when
something has a * by it that means it's conditional on a footnote that
appears at the bottom of the section or page.  Are there footnotes we need
to know about to clarify this?

4) Is this a rackmount server or a tower case?  If rackmount, is it a 1u
server or a 2u server or a 4u server?  Just because the motherboard has 5
slots doesn't mean the case it is installed in will support 5 cards.  A 1u
case rarely supports more than 1 or 2 cards, and always requires a riser
card.  A 2u server rarely supports more than 2 cards unless they are
low-profile.  A 4u server might allow 5 cards, IF the case is designed
with 5 slot openings in the back.

5) Are all the card slots open and available to you at time of shipping?
Many options a customer orders with a server, such as a RAID controller or
additional network ports will fill one or more of the available slots.
You need to be sure all the slots you need are available to you when you
get the server.

As for types of cards.  As others have already said, PCI-X is not
PCI-Express and they are not interchangeable.

A PCI-Express card slot can accomodate any PCI-Express card with the same
number of lanes or less.  So an x8 slot (8 lanes) will support an x1, x2,
x4, or x8 card, but not an x16 card.  I believe the Digium PCI Express
cards are only x1 (one lane) so they should fit in any PCI Express slot,
but you should check with Digium's web site to be 100% sure the card you
are buying is a x1 card.

Unless you specifically buy a low-pofile card, a normal PCI or PCI Express
Card will NOT fit in a low-profile slot.  So assuming Digium's cards are
full height, you only have 3 possible options.  The 2 PCI Express full
height slots, and the 1 PCI-X slot, assuming all those slots are open and
will be available with the case you're using.

I would NOT base my purchasing decision on that vague description given by
the vendor that you have listed in your messages.  I would contact the
vendor and clarify the total number of slots, types of slots, whether they
are open or not, and whether the case will support them all.

Many vendors will use a motherboard with 3-5 slots on the board, in a 1u
rackmount case that only supports 1 physical card.

One final word of warning...  don't try to stick too many cards in one box
without double checking with someone who can tell you if it will handle
that capacity or not.  There were a lot of problems with early Digium
4-port T1 cards where you couldn't use more than 1 or 2 cards at a time
because of the interrupts.  The newer cards, especially PCI Express, may
not have that problem anymore... but I would double check before
proceeding with more than 2 cards in one box.

Can anyone out there clarify (for me as well) whether you can put, say, 4
or 5 4-port T1 cards in a single box now and have it work ok?  Assuming
enough RAM and a fast enough CPU of course.

-- Nick