PCI Express - Semantics 2004-08-14 - By Mark J. Koch
Back
The August 2004 issue of Computer Graphics World finaly had a
PCI Express explanation that finaly made sense to me. Here is a
portion of it ( some paraphrasing on my part):
"In PCIe, a single serial connection can handle up to 500MB/Sec
of data transfer, which is more than quadruple the PCI interface"
"To add even more bandwitdth, PCI Express enables multiple
serial connections to a single device. Called 'lanes', these
connections determine the upper limit of a card's speed. A graphics
card will accomodate up to 16 lanes, for example, while a network
card may accept one or two."
"A PCI Express machine (motherboard) may have several different
types of PCIe card slots. All systems will have a 16x (16-lane) slot
for the graphics card, but manufacturers may divide up the remaining
lanes as they see fit. Initial PCIe chip sets provide for 24 lanes, so you
will see a 16x slot for the graphics card, with the other lanes use by an
8x slot or any comination of 4x and 1x slots."
"Any card fits into any slot, just as long as the slot has enough lanes. A
1x card can work in any slot while a 4x card requires a 4x slot or higher."
-End Quotations-
The bottom line is, read the specs for the motherboard carefully before
buying. If you want to slap two graphics cards in there, you will need to
find a motherboard with two 16x slots.
The other issue is whether the graphics card makes full use of each
channel.
I recently saw a NVidia ad with two dual display cards in adjacent slots,
with a short bridge circuit at the top. Looked like a high end system
but it illustrates that more will be possible with PCI express. It wouldn't
suprise me to see 48-56 channel motherboards in the next year or so.
>-- --Original Message-- --
>From: Dave Angelini
>To: truespace@(protected)
>Sent: 8/13/2004 12:18 AM
>Subject: Re: [TSML] PCI Express - Semantics
>
>So "supporting PCI-Express" means that at some time in the future you
>could
>replace the GPU on the graphics card (for which I am interpretting
>"slot" in
>you explanation below) with one that is designed for PCI-Express??
>
>If that is the case, then this is a bit duplicitous as most users don't
>replace the GPU's on their graphic cards. I find this hard to believe.
>Are
>you referring to something else?
>
>Nevertheless, performance wise, what are you NOT getting with a
>PCI-Express
>"supported" graphics card as opposed to a true PCI-Express graphics
>card.
>The "supported" cards all boost that they have 16 pixel pipelines which
>I
>thought was at the core of PCI-e.
>
>Thanks,
>Dave Angelini
>
>
>
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