PCIe 2.0 Video card in PCIe 1 slot?

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Doc

My initial online searching indicates a PCIe 2.0 card should work in a
PCIe 1 slot but does it perform exactly the same way or do you lose
performance?

Thanks
 
My initial online searching indicates a PCIe 2.0 card should work in a
PCIe 1 slot but does it perform exactly the same way or do you lose
performance?

Thanks
Click to expand...

I thought they were all backwards compatible for higher, even PCIe 4.0
standards. No voltage restrictions on the bus AGP revisions
encounter, as many PCIe cards include independent PS PWR connects to
circumvent impositions on the MB's throughput. Of course, though, you
couldn't really expect a card from 2003 to match 2014 cards,
irrespective of either the MB interface or the card's actual end
channeling deviation and usage, were there actual advantage to being
out of respectively evolving standards. Somewhere in a physical
magnitude of x3 slower transfer rates is at present the imposition
between revisions, discounting such as later encoding. The cards are
designed by MB implementation within some quality and assurance to
negotiate for the videoboard pin strobes as a revision both suitably
recognized and supported. No doubt the implication would contain some
variance between trade names and matching products. I've never owned
nor installed a PCI-e video board for a better sense of experience,
for now running with onboard-chipped video from my MBs offering a PCI-
e slot.
 
Doc said:
My initial online searching indicates a PCIe 2.0 card should work in a
PCIe 1 slot but does it perform exactly the same way or do you lose
performance?

Thanks
Click to expand...

Video cards suffer some performance degradation, below about 1GB/sec
of bus performance.

That corresponds to AGP 4X. So AGP 8X (2133 MB/sec) should be fast enough.

And on PCI Express, PCI Express x4 Rev1.1 would be fast enough.

A PCI Express x16 Rev1.1 slot would be four times faster than a
reasonable minimum.

My Asrock 4Core motherboard, is wired x4 on the video card PCI Express
slot, and I actually use an AGP 8X card in that motherboard. It's one
of the few motherboards, with two video card slots, one AGP, and the
other PCI Express x4 Rev1.1.

Later standards, like PCI Express 2.0 or 3.0, just push the bandwidth
further out.

Also, something that isn't always apparent, is the bandwidth is a lie.

Some chipsets, have a restriction on PCI Express packet size. The
video card slot on my motherboard, is "rated for 8GB/sec" (x16 Rev2), but I
found an obscure web reference the other day, to a theoretical calculation
that says the slot can't really deliver data any faster than 2GB/sec.
It's because the PCI Express packets (max size) is too small.

Because review sites have never measured this, most fan boys believe
what it says on the tin. I don't think I've ever seen a PCI Express
card, designed to do such a measurement. And I don't think the video
card companies provide any such utility (actual transfer rate
measurement during DMA). I think people would be shocked, by
the degree to which their shiny motherboard, was bottlenecked.

In some cases, there isn't enough bandwidth on a chipset bus,
to run everything flat out.

As long as the video slot can do about 1GB/sec, you probably
won't notice. Maybe you'll "lose" by 5% in a video card benchmark,
against someone with a better motherboard. But generally speaking
the impact of the video card slot won't be such that it'll be a
"stutter-fest". My Asrock PCI Express video card slot, would
probably suck a bit of performance/value out of a video card
run in there. My current motherboard, while a bit of a cheater,
probably isn't worse than equivalent of AGP 8X.

http://www.tomshardware.com/reviews/sli-coming,927-9.html

AGP doesn't use packets, so is not affected by that issue.
PCI Express works in a way, like networking. It uses packets
to transfer data. And like "jumbo packets" on GbE, if the
buffers aren't there to hold them, then the biggest possible
packets can't be used.

Paul
 
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