Performance hit from going to pci-e 16x to 8x

[AndrewL]

Like the title says, does anyone have any links with information or charts on the performance hits from switching a card from the pci-e 16x to the 8x slot.
I moved my 7800gt from the top slot to the lower slot because for some reason or another the top slot is producing errors in ati tool while the bottom slot isnt. Is my card running 8x right now then? if I remember correctly the bottom slot on a DFI ultra-d is 8x right.

 

[BobDaMenkey]

Why are you using ati tool with an nVidia card?

And it shouldn't affect performance all that much. Modern video cards are only just saturating the old AGP 8x bus.

 

[schneiderguy]

there should be zero performance difference between pci-e 16x and 8x, at least on current generation or lower cards.

 

[schneiderguy]

Originally posted by: BobDaMenkey
Why are you using ati tool with an nVidia card?

ATI tool works for nvidia cards too

 

[BobDaMenkey]

Originally posted by: schneiderguy

Originally posted by: BobDaMenkey
Why are you using ati tool with an nVidia card?

ATI tool works for nvidia cards too

It just seems wrong though.

 

[AndrewL]

Well coolbits overclocking sucks because you cant stability test it. The automatic clock setting thing it has is always is innaccurate. The only other thing I could use is powerstrip and I like ati tool better.

 

[Missing Ghost]

The bottom slot on the dfi is 2x. There are two modes you can trigger on that mobo using the jumpers. One is 16x/2x, the other one is 8x/8x.

 

[AndrewL]

Originally posted by: Missing Ghost
The bottom slot on the dfi is 2x. There are two modes you can trigger on that mobo using the jumpers. One is 16x/2x, the other one is 8x/8x.

Thanks i new the jumpers affected the speeds of the slots i just forgot the specifics. My manual should say how to switch it to 8x/8x right

 

[TheRyuu]

Originally posted by: BobDaMenkey

Originally posted by: schneiderguy

Originally posted by: BobDaMenkey
Why are you using ati tool with an nVidia card?

ATI tool works for nvidia cards too

It just seems wrong though.

I think it's wrong. Thats what we have RivaTuner and Coolbits for. (ok, you can use Rivatuner on both )

We (Nvidia People) also have NV Tray as well

Edit: And NO performance difference. At least on todays cards.

 

[AndrewL]

Well im sure theres definitely a difference on 2x. Thanks ghost, for pointing that out. Rivatuner is ok NV tray is okay but i still like ati tool better.

 

[Big Lar]

When you go into the Genie section of bios, about half way down it will tell you the mode you are running in as to pci-e. 2x is not enuff for todays vid cards, however 8x is fine with only a sligt hit on performance.

Dfistreet has some info on the subject, so you can probably pull up the benchmarks on a search there.

 

[AndrewL]

The odd thing is even though the top slot causes errors in ati tool i can pass 3dmark 05 without crashing (although its possible it is artifacting in a way i cant see). I wonder how a slot could still function but be the source of crazy errors like this.

 

[JBT]

I ran my X1900XT in 2x mode for awhile. There was no performance difference from 16x, 8x or 2x.

 

[AndrewL]

Alright so now i switched it to 8x per slot and now the bottom slot is causing errors. Im not sure what the source of the problem is anymore. Is it the card or is it the mobo?

I know heat is not a problem with the card. It has a nice copper heatsink with a good fan and the temps are low not to mention the side panel is off. The errors being caused are not a result of heat or an overclock basically at any frequency even the lowest the card can go on both core and mem it errors as soon as I start the scan for artifacts test.

The problem was solved when i was using 2x speed, but certianly 2x is somewhat slower than 8x and id prefer not to use 2x if I dont have to. Any ideas?

 

[AndrewL]

Cmon surely someone has had a similar problem to this.

 

[AndrewL]

Alright now the problem is getting even more complicated. When I run atitool artifact scan it will error immediatly if I run it right after I open up ati tool, but if i click close 3d view then run it it runs stable. I found this bizzare so I set the mem and core clocks to some absurd values that i knew it wouldnt be able to run stable for a second and yet its detecting no errors (after using the close 3d view then test method). So im thinking its a software related issue.

Anyhow in one simple sentence can anyone recommend some good artifact scanning software? I know about 3dmark but it doesnt detect artifacts so that wont fit the bill.

 

[Rectro]

Im having to run my Nvidia 7950 GX2 on a 8X slot. Now I know that one GPU mite not have a hit but what about 2, in this case the GX2?

Big Lar If theres only a slight hit on a single card at 8X then I asume im getting a much bigger hit having 2 GPUs.