Reduced PCI express speed when using 2 slots?

Mike1983

Mike1983

Mike1983

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Hi

I've got an Abit IP35 Pro motherboard and have an 8800GT installed as well as a Xonar D2X (uses a PCI Express slot).

One of my friends seemed to think that the fact I've got the Xonar installed in the 2nd PCI slot will bring the speed of my 8800GT down.

I've read the motherboard manual and I think he is wrong but can anyone on here confirm this please?

The manual seems to indicate that the only way speed would be affected would be if I had the 8800GT installed in the 2nd slot (which is not the case). My 8800GT is installed in slot 1 which the manual indicates is x16 bandwidth, the Xonar is installed in slot 2 which the manual indicates is x4 bandwidth.

Have I got this correct? And didn't know whether to post this here, graphics card or sound card forums.

Thanks

Mike
 
You are correct.

Also, I even think the D2X only requires a 1X slot..and you have one of those as well
 
Thanks

Good to know I'm right.

I thought the D2X was PCI-E only (my mobo only has 2x PCI-E, the rest are standard PCI)? Either way I've no ambition to put any new cards in in the near future so no worries.

Edit, yes I've just seen the manual and note there's a x1 slot too. Thanks for pointing that out, might swap it over the next time the case is open.

Mike
 
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Looks to me like you have a 1x PCI-E just to the right of the main PCI-E 16x slot

ip35_pro_top_500.jpg
 
Yes, I think I spotted it in the manual just as you was posting your reply. Thanks for pointing it out.

Just had a look inside the case to weigh it all up but I wouldn't be able to put the D2X there as the card will likely be touching the ram on its own. It also has a power connecter that will definitely hit the RAM so it's not an option.

At least I know I have it their in future though for a smaller card :)

Thanks

Mike
 
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This is very interesting, basicly I had the same quistion, but with the opposite answer:

LOOK HERE

I whanted to raid some SSD´s using an Adaptec 2405, (PCI-E X8), and this was even
on the more recent P45 Chipset, in short I was told that as soon the X8 was inserted
the main PCI-E X16 grapic slot would be reduced to X8 also unfortunately and I would
have to use an even newer P38 or P48 chipset with true PCI-E slot-seperation in orde
to overcome this limitation, I had to give up the hole project becourse these chipset is
a deadend if you whant 4x4 16 GB Ram later, could someone throw some more light ??

It seems like, from reading this, that its NOT nessesary to go P38/P48,...
 
Now I'm confused lol

Is there any way of confirming by software what speed (bandwidth) the graphics card is operating at i.e. whether it is x16 or x4 reduced rate?

3DMark and CPU-Z both refer to x16 on my system with the Xonar installed.

To settle it and put my mind at ease I might do 2x 3DMark runs tonight, one with the Xonar installed and one without.

Mike
 
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HHM said:
This is very interesting, basicly I had the same quistion, but with the opposite answer:

LOOK HERE

I whanted to raid some SSD´s using an Adaptec 2405, (PCI-E X8), and this was even
on the more recent P45 Chipset, in short I was told that as soon the X8 was inserted
the main PCI-E X16 grapic slot would be reduced to X8 also unfortunately and I would
have to use an even newer P38 or P48 chipset with true PCI-E slot-seperation in orde
to overcome this limitation, I had to give up the hole project becourse these chipset is
a deadend if you whant 4x4 16 GB Ram later, could someone throw some more light ??

It seems like, from reading this, that its NOT nessesary to go P38/P48,...
Click to expand...

Different situation entirely.

If the OP situation, no it won't effect the 8800's speed as he has 3 fixed speed PCI-E slots.

16x PCI-E 1.1
4x PCI-E 1.1 (16x Physical)
1x PCI-E 1.1

As the speeds are fixed it doesn't matter which slots he uses it will not affect the others.

So GPU in the 16x slot, will not change if he then uses annother slot.




HOWEVER



In your case it WOULD affect your GPU speed (I am assuming you are on a P45 chipset here based on the advice you were given). Why? Because the P45's PCI-E slots are dynamic.

The moment you insert a card into the 2nd PCI-E (16x Physical) slot the board splits the main PCI-E channel into 2 x 8x PCI-E 2.0 slots.

As such your GPU would drop down to 8x PCI-E 2.0, and the RAID card would use 8x PCI-E 2.0 in the 2nd slot.

Now while that may sound rubbish, it isn't that bad as PCI-E 2.0 is twice as fast as PCI-E 1.1, as such an 8x PCI-E 2.0 slot is equivalent to a 16x PCI-E 1.1 slot, which is more than enough for most GPU's out at the mo (would limit a 4870X2/GTX280 a bit, rest would be fine).

If you went with an X38/X48 you would have double the lanes of a P45 to play with, as such fitting the 8x PCI-E card would still leave the main GPU 16x PCI-E 2.0.
 
HeX said:
The moment you insert a card into the 2nd PCI-E (16x Physical) slot the board splits the main PCI-E channel into 2 x 8x PCI-E 2.0 slots.

As such your GPU would drop down to 8x PCI-E 2.0, and the RAID card would use 8x PCI-E 2.0 in the 2nd slot.

Now while that may sound rubbish, it isn't that bad as PCI-E 2.0 is twice as fast as PCI-E 1.1, as such an 8x PCI-E 2.0 slot is equivalent to a 16x PCI-E 1.1 slot, which is more than enough for most GPU's out at the mo (would limit a 4870X2/GTX280 a bit, rest would be fine).
Click to expand...

Thanks HeX !! taking the time, I get the picture now, or at least I fell :D

Yes, P45, GA-EP45-UD3P I guess, for various reasons, (f.ek. 16 GB Ram)

• 1 x PCI Express x16 slot, running at x16
• 1 x PCI Express x16 slot, running at x8
(The PCIEx16 and PCIEx8 slots support ATI CrossFireX technology and
conform to PCI Express 2.0 standard.)
• 3 x PCI Express x1 slot

Im NOT a gamer, "just" need dualhead 2x 1920 x 1200 >60hz operation
with my HD2600XT/256, for used with Sony Vegas video-editor that is
told not to be GPU-heavy, but still I need relatively high resolutin X2 !

So THIS is what it boils down to, if the 2600XT can handle this in "X8"

If anyone can help a little here I will be happy, but maybe I should do
a new thread in the "Graphics Card" sub-forum,. I see now that many
things are playing together,..... but also I get a little hope that X8 is
actually sufficient for my use, thanks again,...
 
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