# Bus Interface question



## dark2099 (Jan 2, 2013)

So I was currious W1zz, with the bus interface in GPU-Z, how is that read/calculated?  As you can see, I am on a P67 with a 3770k, but GPU-Z is saying my 7950 is running PCI-E 3.0?  Is there any way this is possible?


----------



## Naki (Jan 2, 2013)

I assume you mean your motherboard supports PCI Express 2.0 only, but GPU-Z (incorrectly) shows 3.0, right?


----------



## dark2099 (Jan 2, 2013)

Well I know some later model Z68 board supported 3.0, and other funny thing, Biostar's website only lists version 5.0 and 5.1 for my MB, but mine has 5.2 printed on it, so wondering if they took some z68, someone kinda made it a p67, but left the 3.0 support.  Or as someone else told me, its just reading the standard, not the actual performance.


----------



## drdeathx (Jan 2, 2013)

Glitch in GPUZ


----------



## Naki (Jan 2, 2013)

I get the same "issue" (bug/glitch?) - my ASRock motherboard is clearly a PCI Express 2.0 motherboard (although there was a later update that did support 3.0), yet GPU-Z says PCI Express 3.0, which can not be. My videocard is a Nvidia GeForce GTX 670 (2 GB of videoRAM).

Maybe the maker of the app can comment on this?


----------



## dark2099 (Jan 2, 2013)

My guess is either a glitch, or like I mentioned is reading the standard the card/cpu is capable of rather than what its actually running.


----------



## Naki (Jan 2, 2013)

dark2099 said:


> My guess is either a glitch, or like I mentioned is reading the standard the card/cpu is capable of rather than what its actually running.



Nope, on some other systems of mine it does say even PCI Express 1.1 (at idle). Then when you load up the GPU (via the GPU-Z Stress test for example), the reading goes to PCI Express 2.0/etc.


----------



## Jstn7477 (Jan 2, 2013)

If your PCIe slot is wired directly to the CPU, it should support PCIe 3.0. If it's behind lane switches that aren't PCIe 3.0 supportive, then it should read 2.0.


----------



## drdeathx (Jan 2, 2013)

Jstn7477 said:


> If your PCIe slot is wired directly to the CPU, it should support PCIe 3.0. If it's behind lane switches that aren't PCIe 3.0 supportive, then it should read 2.0.



His board does not support 3.0. The GPU runs in 2.0 no question about it. It is a glitch, no question about that either. Look at the specs of your board...


----------



## W1zzard (Jan 3, 2013)

GPU-Z reads that info directly from the GPU and has never been wrong. Any other software will tell you the same.

Are you able to switch to 2.0 using the BIOS to compare performance?

You should be able to see differences using Unigine Heaven: http://www.techpowerup.com/reviews/Intel/Ivy_Bridge_PCI-Express_Scaling/22.html


----------



## Naki (Jan 3, 2013)

W1zzard said:


> GPU-Z reads that info directly from the GPU and has never been wrong. Any other software will tell you the same.
> 
> Are you able to switch to 2.0 using the BIOS to compare performance?
> 
> You should be able to see differences using Unigine Heaven: http://www.techpowerup.com/reviews/Intel/Ivy_Bridge_PCI-Express_Scaling/22.html



How exactly did you switch from PCI Express 3.0 to 2.0 and 1.1? What section of the BIOS is that setting in?
What motherboard did you use for the test?
I am not 100% sure, but I don't think my ASRock motherboard BIOS has a "PCI Express speed" setting.
My motherboard is this one:
http://www.asrock.com/mb/overview.asp?Model=Z68 Pro3

There is also another newer board with the same name, but with the added "Gen3" word:
http://www.asrock.com/mb/overview.asp?cat=Specifications&Model=Z68 Pro3 Gen3
My motherboard is clearly NOT this one, but one with PCI Express 2.0 only.


----------



## Aquinus (Jan 3, 2013)

Naki said:


> How exactly did you switch from PCI Express 3.0 to 2.0 and 1.1? What section of the BIOS is that setting in?



I don't know about your BIOS but mine refers to it as forcing Gen1, Gen2, and Gen3.


----------



## Naki (Jan 3, 2013)

Aquinus said:


> I don't know about your BIOS but mine refers to it as forcing Gen1, Gen2, and Gen3.


Which section of the BIOS settings?? It is an Intel chipset (and thus Intel CPU also) motherboard, right?
Is your motheboard ASUS P9X79 Deluxe?


----------



## Aquinus (Jan 3, 2013)

Naki said:


> Which section of the BIOS settings?? It is an Intel chipset (and thus Intel CPU also) motherboard, right?
> Is your motheboard ASUS P9X79 Deluxe?



Yeah, here. Let me restart, I'll take a screenshot of my BIOS for you to give you an idea what sections of your BIOS it could be in.

Edit: Here we go.







I just keep mine set to GEN3. Since I have 2.0 cards, they just drop down to the fastest it can do.


----------



## Naki (Jan 3, 2013)

Thanks!! I don't think my motherboard has such a setting, but maybe it could be in a different section than your ASUS board. Will check it later today and report back...


----------



## dark2099 (Jan 9, 2013)

W1zzard said:


> GPU-Z reads that info directly from the GPU and has never been wrong. Any other software will tell you the same.
> 
> Are you able to switch to 2.0 using the BIOS to compare performance?
> 
> You should be able to see differences using Unigine Heaven: http://www.techpowerup.com/reviews/Intel/Ivy_Bridge_PCI-Express_Scaling/22.html



Horribly slow at responding, so you're saying if GPU-Z says PCI-E 3.0 it is reading from the active state the card is using?  And I'm not sure, just got a new setup, so don't have that board running.  Maybe will do a quick box setup to double check some of that out.


----------



## W1zzard (Jan 9, 2013)

dark2099 said:


> Horribly slow at responding, so you're saying if GPU-Z says PCI-E 3.0 it is reading from the active state the card is using?



that's correct


----------



## cadaveca (Jan 9, 2013)

P67 and Z68 can both do PCIe 3.0 no problem with IVB, as long as the primary slot is the only one that is populated and no switches are in place, or the switching hardware is PCIe 3.0 complaint. Even if it's not complaint, PCIe 3.0 encoding on PCIe 2.0 bus can be used as well, since the bus is not saturated with data, and PCIe 3.0 encoding is more efficient.


----------



## Naki (Jan 9, 2013)

cadaveca said:


> P67 and Z68 can both do PCIe 3.0 no problem with IVB, as long as the primary slot is the only one that is populated and no switches are in place, or the switching hardware is PCIe 3.0 complaint. Even if it's not complaint, PCIe 3.0 encoding on PCIe 2.0 bus can be used as well, since the bus is not saturated with data, and PCIe 3.0 encoding is more efficient.


Um, yeah?? So what is the purpose of the motherboard ASRock Z68 PRO3 Gen 3 compared to the board ASRock Z68 PRO3? 
I am pretty sure the second motherboard (which I have) has PCI Express 2.0 only, it can't magically start supporting PCI Express 3.0 all of a sudden. Only the Gen 3 board supports it!


----------



## cadaveca (Jan 9, 2013)

Naki said:


> Um, yeah?? So what is the purpose of the motherboard ASRock Z68 PRO3 Gen 3 compared to the board ASRock Z68 PRO3?
> I am pretty sure the second motherboard (which I have) has PCI Express 2.0 only, it can't magically start supporting PCI Express 3.0 all of a sudden. Only the Gen 3 board supports it!



You are right, if that board was built with PCIe 2.0 switching hardware, it cannot negotiate the full PCIe 3.0 x16 link, but it can still use PCIe 3.0 encoding. Some boards even switch down to PCIe 3.0 x8 in that instance, actually.


Because the whole PCIe 3.0 thing was such a fiasco, with many OEMs calling out other OEMs, I did test this whole thing, found nothing truly interesting, and dropped the subject. *As long as IVB is used, and has direct link to GPU, PCIe 3.0 is most definitely possible.*


When board makers updated boards, they made it so that functionality-wise, you get x8/x8 PCIe 3.0, but  *by ONLY changing the switching hardware to PCIe 3.0 bridges*.. which were not available when the platform launched. Boards that did not get such updates do some rather strange stuff, honestly, but still most will do PCIe 3.0 x8 to primary slot.


This is why I picture such switching components in my reviews, close up. These are tiny little chip that most reviewers don't even bother to mention. These are the single change that is responsible for adding FULL PCIe 3.0 support.

What's even more interesting, to me, is that many AMD AM3+ boards use PCIE 3.0 switching hardware, but can only do PCIe 2.0. Board makers have just started to use PCIe 3.0 switches all around.


----------



## Naki (Jan 9, 2013)

cadaveca said:


> You are right, if that board was built with PCIe 2.0 switching hardware, it cannot negotiate the full PCIe 3.0 x16 link, but it can still use PCIe 3.0 encoding. Some boards even switch down to PCIe 3.0 x8 in that instance, actually.


No, they do NOT switch to that!
However, the speed of PCI Express 2.0 16x is equal to PCI Express 3.0 8x, maybe that is what got you confused.

EDIT: Yeah, I heard about the so-called "Fake PCI Express 3.0" vs. "Real PCI Express 3.0" boards, but MY BOARD is ONLY PCi Express 2.0 (and does not claim to support PCI Express 3.0 in any way), so I was NOT discussing that thing you mention.


----------



## cadaveca (Jan 9, 2013)

Naki said:


> No, they do NOT switch to that!
> However, the speed of PCI Express 2.0 16x is equal to PCI Express 3.0 8x, maybe that is what got you confused.
> 
> EDIT: Yeah, I heard about the so-called "Fake PCI Express 3.0" vs. "Real PCI Express 3.0" boards, but MY BOARD is ONLY PCi Express 2.0, so I was NOT discussing that thing you mention.



Yeah, that fiasco is caused by this "issue" of what supports what. Some board makers "force" PCIe 2.0 in BIOS, but at the same time, most P67/Z68 PCIe x16/x4 boards work perfectly fine.

If the BIOS doesn't force PCIe 2.0 when IVB is installed, many different scenarios are possible, and it's all dependant on what switches are used, what the BIOS does, etc.

Take a look at all the OEM claims on the issue, and you'll find the answers. I had to ask them all directly, and many did not like me asking, and this caused some issues. I won't forget that whole episode, let me tell you.


----------



## Jetster (Jan 9, 2013)

Mine does the same thing and I have a Sandy Bridge + P67


----------



## cadaveca (Jan 9, 2013)

Jetster said:


> Mine does the same thing and I have a Sandy Bridge + P67






THAT is not right. 

I wonder what's up there. 

These are the bridge chips:

PCIe 3.0:

NXP:






ASMedia:






Pericom:






PCIe 2.0 ASMedia:






I wonder which ones your board has?


----------

