question about PCI slots (HP xw8400)

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Simple question for hardware guru, but I have to make sure is exactly
what we need. There is workstation HP xw8400, and we basically need 5
PCI slots 4 of them will be fill by normal PCI cards and one will fill
by half length PCI card. So basic question is: is it possible with that
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In spec i have 3 normal PCI and 3 PCI-X, so should be ok, but I want to
make sure before ordering. Thanks in advance.


Re: question about PCI slots (HP xw8400)

whitey wrote:
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NO!  That machine has only 1 PCI slot and 3 PCI-X. The others are 3 PCIe
  and are not compatible, so your one short.

Re: question about PCI slots (HP xw8400)

whitey wrote:
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There aren't a lot of motherboards with five PCI slots any more.
The boards have more PCI Express slots, which are not compatible.

This is an example of one that still has five PCI slots. GIGABYTE GA-P35-S3G.

PCI-X and PCI at least, share the same bus structure. But PCI-X
slots run at higher clock speeds, and have 3.3V for the bus
voltage. The regular PCI slot may use 3.3V or 5V for I/O, at
the motherboard designer's discretion. Ideally, your PCI cards
may be universal keyed (work with 5V or 3.3V), or be 5V powered
(in which case they'll work with a lot of older motherboards). The
slots or keyways in the edge connector, determine whether the
card will fit into the slot, when you try to fit it.

So in fact, you have a lot of questions to ask. You should
examine the PCI cards more carefully, to decide whether they
are PCI-X type or PCI type. Expensive RAID cards, for example,
might be PCI-X, due to their bandwidth requirements for
storage devices.

PCI and PCI-X are examples of parallel busses. The bus is shared
and connected to all the slots on the same bus segment. The
bandwidth is shared as well. So if you had five 32 bit PCI slots,
there is a maximum of 133MB/sec available at any one time, shared
by the slots. (Assuming the normal 33MHz desktop motherboard
clocking scheme - and the parallel bus is 32 bits wide.)

PCI Express is a newer design, where the connection between the
motherboard chips and each slot is point to point (not shared).
Interconnect is high speed serial. Each serial link is called
a "lane" and offers 250MB/sec bandwidth. Thus, even the
PCI Express x1 slot, having only one lane, gives a private
connection to the chipset (not shared by other slots), and has
double the bandwidth of the (shared) basic PCI slot.

Graphics cards now use a PCI Express x16 sized slot. The slot has
so many pins, because there are 16 differential TX and 16
differential RX pins, to carry the 16 lanes of bus interconnect.
That is a total of 64 pins, which is why the slot is longer,
and the slot size is comparable to older technologies. But
with 16 lanes, the bandwidth available is 4GB/sec.

Wikipedia has a couple articles, but they didn't answer all my questions.

(PCI-X 66MHz, 100MHz, 133MHz, 64 bit wide parallel bus, shared,
small number of slots per bus segment, due to speeds involved. 3.3V I/O.
While there is a revision 2 for PCI-X, I don't know how widespread
it has become.)

(PCI cards. 33 or 66MHz. 32 or 64 bit busses. 3.3V or 5V slots)

In the newer PCI Express slot types, the physical connectors are
different sizes, depending on the number of lanes they want to
support for that slot. For example, in the following picture,
from top to bottom, are x4, x16, x1, x16 PCI Express, with the
bottom one being the older PCI 32 bit slot (5V keyed).

If you have a bunch of PCI cards that must go into a new
computer, and the new computer has a bunch of "useless" slots
in it, there is an alternative. This product comes with an
option for a PCI Express x1 card, that plugs into the new
computer, and runs an "extension cord" to an expansion
chassis. The expansion chassis is used to hold your PCI cards.

In bullet point 6 in that document, you can see they have host bus
adapter cards for a variety of computer slot types. That expansion
chassis can even be connected to a laptop with ExpressCard slot.
Note that they have more than one expansion chassis type, and you
can get a PCI chassis or a PCI-X chassis etc.

While those expansion products are expensive, they can solve the
problem. If the expansion chassis costs more than $1000, then in
some cases, it may be cheaper to buy new cards instead. Since some
people need legacy support, which is not provided by new cards,
then that is when the $1000+ is well spent.


Re: question about PCI slots (HP xw8400)

Your question is not very clear.  But you need to know that:
are three different non-compatible architectures.
Going back to your question, it would appear that that computer will NOT be
suitable for your puposes.


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Re: question about PCI slots (HP xw8400)

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Actually, many PCI cards can be used in a PCI-X slot. Several PCI-X cards
can also be used in PCI slots as well.

Re: question about PCI slots (HP xw8400)

Calab wrote:
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And you can have a devil of a time getting that info for some
cards. For example, some Adaptec controllers can be plugged
into an ordinary PCI slot, and work. But to do that, it helps
to find the relevant page on the Adaptec site, and "get it in

I wish sites like would do their jobs, and write
decent primers on PCI/PCI-X etc., so other people don't have
to explain this stuff. Any time that copies of standards
are only available at a price, it means consumers are limited
as to where they can get the necessary information.


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