"Gary Townsend" said:
As a follow up his mother board has one PCI 64 slot on it already its just
taken up by a video card and he wants to add a firewire card which is also
PCI 64 to it. So as a substitute is one able to expand ther 64 bit pci slot?
One way to do this, is with an expansion chassis.
http://www.mobl.com/expansion/products/pci_expansion/7slot6466/index.html
You plug the transmitter card into your current PC. The high speed
links plug into the expansion chassis somewhere. Then, the two 64
bit PCI cards you want to use, would be plugged into the expansion
chassis.
When bridged like this, there is a transmission delay for each bus
transaction. That means, if the software uses polled transfers (CPU
doing single cycles), those operations on the cards in the
expansion chassis will seem slower than before. Whenever DMA is
being used, and assuming the cards are using decent sized bursts,
this delay becomes less noticeable (so data transfer phases are
less affected than control/setup operations). So, this solution is
not a perfect one, by any means.
My purpose in posting this, was to show it is technically possible
to "make more slots" for a computer, but for most people the
solution is too expensive.
This chip is an example of a bus bridge - it is a commercially
available chip for "making more slots". There are a ton of these out
there, some coming from smaller companies (bridge chips are sometimes
used on those combo USB/Firewire/Ethernet PCI cards). The solution in
the expansion chassis above is more sophisticated than this, because
of the lengths of high speed cable allowed between boxes. Effectively,
it is like the chip in this Intel document is sawed in half, and
high speed links connect the two halves. (It could just be
two bridge chips in a row.)
http://support.intel.com/design/bridge/quicklist/25297401.pdf
Another thing to watch for, is I believe there is some limit to
how many levels of bridging can be used. That means, if you were
to plug a combo USB/Firewire/Ethernet card into the expansion
chassis, there could be issues. Since I don't have a complete
set of PCI standards, I cannot help with what that limit might
be. (It might be just a software limitation - ask someone at
mobl.com to find out for sure.)
http://www.mobl.com/expansion/support/faqs/pciexp.html
Another option, is a riser card. The PCITX8-31 here, for
example. I have no idea what kind of issues a simple riser
card can cause. At least there is no bridging delay with
one of these. And since there is no silicon (that I can see),
the product should be dirt cheap. Ask plenty of questions
before purchasing!
http://www.adexelec.com/pci64.htm
Paul
