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PCI vs modified PCIe x1

Last response: in Graphics & Displays
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December 31, 2008 11:40:29 PM

Hello everyone!

I've been given the challenge of making an old company HP more useful with limited supplies. After extensive investigation and reading through forums, I am left with one critical question.

Which will be faster? The PCI Radeon 7000 series currently in the computer, or putting a PCIe GeForce 7600 GS 512 MB in a modified PCIe x1 slot?



Here is what I discovered and what I'm still dubious about:

-The HP I'm using (Compaq dc5700 Microtower) has no PCIe x16 slot. Well to be more specific, it has a PCIe x16 slot with a different pin configuration (SDVO/ADD2-N format) that will only support HP's proprietary video cards. Something I would expect from Dell, not HP, but I digress.

-The motherboard has two PCI slots and one PCIe x1 slot.

-There is currently a Radeon 7000 in the PCI slot

-I have a PCIe GeForce 7600 GS I can use to upgrade the computer

-After much research, I discovered one can put a PCIe x16 card into a PCIe x1 slot. The downside is that only one of the 16 data channels will be used in that scenario, causing a significant bottleneck.

-Even if the PCIe x1 slot is close-ended, which mine is, it is relatively easy enough to grind away the back part of the PCIe x1 slot to allow the rest of the video card to poke out the pack.

-This computer is not being used for games, it is an employee computer being used for light image editing and coding.



The following is what I haven't been able to figure out yet.

-Even though using the modification method would put a significant bottleneck on the performance of the PCIe video card, a PCIe x1 slot still has almost twice the bandwidth as a PCI slot.

Bus Bandwidth
PCI 132 MB/s
AGP 8X 2,100 MB/s
PCI Express 1x 250 [500]* MB/s
PCI Express 2x 500 [1000]* MB/s
PCI Express 4x 1000 [2000]* MB/s
PCI Express 8x 2000 [4000]* MB/s
PCI Express 16x 4000 [8000]* MB/s
* Serial total

So in theory, the bottlenecked video card should still perform better then the PCI video card.

-The real question is, how good are the PCIe videocards/motherboard slots at scaling the performance of the video card? I'm concerned that, although the GeForce will have access to a PCIe x1 slot and thus more bandwidth then what the Radeon has access to, the Radeon will still perform better as that Radeon card is in the slot it was designed for.

The above proposed question seems to be a bit too conceptual to get a straight answer from a google search. Any help would be greatly appreciated! Please let me know if there is any important information I left out.

Thanks!
-Geoffrey



Sources:

Bandwidth specs
http://www.tomshardware.com/forum/249677-33-socket-exte...

Format of HP slot
http://forums13.itrc.hp.com/service/forums/bizsupport/q...

Discussion of if an x16 card will work in an x1 slot
http://www.tomshardware.com/forum/247979-28-express-vid...

Experimental proof that putting an x16 card in an x1 slot works
http://www.tomshardware.com/forum/249291-30-card

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