# PCI Express Frequency



## Troy210 (Sep 26, 2008)

In my bios, there is an option to move this setting from 100 to 166..what is this? Is there an advantage to bumping this up?


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## gerrynicol (Sep 26, 2008)

llllllllllll said:


> In my bios, there is an option to move this setting from 100 to 166..what is this? Is there an advantage to bumping this up?



Kinda, some people find that raising this brings stability, but it's only ever a few Mhz.  I would leave that alone at this point in time untill you are able to get a stable CPU o/c


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## Troy210 (Sep 26, 2008)

So..it makes my video card faster?


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## gerrynicol (Sep 26, 2008)

No no, it makes the PCIe slot stable, it will not increase speeds


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## Kursah (Sep 26, 2008)

I've tried increasing from 100 on different boards and cards, really with little to no effect on anything performance-wise. You may gain a couple FPS or a few points in a benchmark, but don't expect too much from this. Increasing to 105-110 may in some instances help with a system overclock, more of a trial and error kind of situation tho.

I would say lock it at 100MHz and call it good! That's just from my experience tho.


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## imperialreign (Sep 26, 2008)

Kursah said:


> I've tried increasing from 100 on different boards and cards, really with little to no effect on anything performance-wise. You may gain a couple FPS or a few points in a benchmark, but don't expect too much from this. Increasing to 105-110 may in some instances help with a system overclock, more of a trial and error kind of situation tho.
> 
> I would say lock it at 100MHz and call it good! That's just from my experience tho.





I agree.  From a lot of testing I've done with quite a few ATI cards - on OCed systems, 105-110 will net a small performance boost.  Over 110, any noticeable performance plateau's, and upwards of 130+ it actually hurts performance.  This is all just a generality, as I don't have access to a ton of hardware to test out many configurations . . . based only on testing og my equipment.


But, if you have an ASUS board, set it to [AUTO] and let the BIOS handle it - I've had the biggest performance increase when set to auto, as compared to any other setting.

Be warned, though, setting PCIE frequency too high can potentially damage the PCIE slot, the card, or your board.


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## Kursah (Sep 26, 2008)

That and on some intel boards, at least the ones I've used, going over 120 will make SATA drives dissapear! Just return to below 120MHz and the drives will return unharmed...to me it wasn't worth it for the unnoticable performance possibility...so back to 100 I've gone and left it there.


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## KBD (Sep 26, 2008)

as others have said dont f**k with it. Its actually better to lock it at 100 because any FSB overclock will raise your PCI-e frequency as well. Thats how it works on my AMD nforce board anyway, it could be diffrent on yours.


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## imperialreign (Sep 26, 2008)

Kursah said:


> That and on some intel boards, at least the ones I've used, going over 120 will make SATA drives dissapear! Just return to below 120MHz and the drives will return unharmed...to me it wasn't worth it for the unnoticable performance possibility...so back to 100 I've gone and left it there.



odd - but that's an Intel board, eh? 

I really wish I had access to the hardware to investigate PCIE Frequency settings more, or at the very least one of the big tech sites would get off their bumm and dig into it some more.

It's one of the few aspects of a BIOS config that not much information exists for, and understanding of it is vague and inconclusive - it seems many sites have different opinions and experiences regarding it as well, which only further muddies the issue.


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## hat (Sep 26, 2008)

PCI-E is locked on mine. I usually have mine at 102 or 103. 166MHz is way too much for the PCI-E bus and will almost certianly give you some very strange probelms later on. Speaking from personal experiance here. I had mine at 125 and it corrupted my operating system. I had to reformat.


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## AphexDreamer (Sep 26, 2008)

Might I note that increasing it to anything higher than 105 might lead to data corruption on your Hard Drive and that's more likely to happen if you have an RAID set up. I know this hands on.

Yeah what hat said above... Didn't see that sorry.


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## Fastmix (Sep 26, 2008)

Bottom line..it's just not worth it.


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## Gilletter (Sep 26, 2008)

... why do they let us play with stuff like that, knowing all too well someone is going to max it out JUST to see??? lol


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## Kursah (Sep 26, 2008)

The same reason that we're allowed to play with memory timings that can go way lower than a lot of what's out there at many different speeds...it was something that was allowed as an adjustable features in many bioses. There were rumors a while back that some boards would kick up to 120MHz on PCI-E for certain NV/ATI cards...dunno if this ever proved true. I've seen some NV MB users with NV cards hit 140-150 on the PCI-E bus and have some performance increase, again nothing to write home about.

Maybe there is something in the future that may utilize a faster PCI-e bus speed, who knows for sure. But if they give us the option to mess with it, we gotta try it out and see what happens...human nature!


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## m4gicfour (Sep 26, 2008)

I thought I read somewhere about nVidia cards using the PCIe bus clock, in combination with a divider as a reference in computing some sort of rate (core clock maybe? I don't think it was, but I can't remember); so increasing PCIe would actually overclock (albeit very minutely) your card. I don't remember the straight facts though, and I can't find the source, so I guess it didn't happen


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## JC316 (Sep 26, 2008)

I always lock it at 100. I have heard horror stories of dead cards from messing with it.


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## Kursah (Sep 26, 2008)

I'm sure that was on this site, I know reference 9600GT's had a link on the card that multiplied clocks based on the PCI-e bus. I had a non-reference 9600GT that was not affected by this, I don't know many users that went that route in reality. I'm not sure if 9800's are similar or not with that kind of overclockability option.

The source was here...just find the first 9600GT review...it's a few pages back on the reviews. Dunno what happened to the article tho.


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## m4gicfour (Sep 26, 2008)

Kursah said:


> I'm sure that was on this site, I know reference 9600GT's had a link on the card that multiplied clocks based on the PCI-e bus...



Should've known! 

I do remember that now that you mention it. I wonder if any of the ATi cards have a similar link.


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## gerrynicol (Sep 26, 2008)

Ituses the pci frequency to generate the clock for the card iirc


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## 3870x2 (Sep 26, 2008)

The frequency is the bandwidth at which the card does, however the card fixes its own frequency via the bios.  By setting the PCI-E freq up, your card will underclock to keep itself at its stock bios or overclocked frequency.  This was set up more as a troubleshooting/testing feature, and not meant for video cards at all.


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## imperialreign (Sep 26, 2008)

One other point I forgot to mention earlier, but was hinted at in Kursah's post . . .


the PCIE frequency setting for most motherboards does not just affect your video card.  It affects all components tied in to the PCIE BUS.  If you motherboard integrates any SATA or IDE controllers, it will affect them . . . onboard WiFi on PCIE, it will affect that as well.  Even your onboard audio.

It depends on what is tied into the PCIE BUS as to what all will be affected - but it can lead to a massive headache down the road as well.


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## largon (Sep 26, 2008)

3870x2 said:


> The frequency is the bandwidth at which the card does, however the card fixes its own frequency via the bios.  *By setting the PCI-E freq up, your card will underclock* to keep itself at its stock bios or overclocked frequency.


Got a link to support that? 
Never heard anything like that. 


JC316 said:


> I always lock it at 100. I have heard horror stories of dead cards from messing with it.


Never heard any such stories, either. 
Link? 



imperialreign said:


> Be warned, though, setting PCIE frequency too high can potentially damage the PCIE slot, the card, or your board.


Same BS can be said about _overclocking anything_.


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## Deleted member 3 (Sep 26, 2008)

First of all, 166MHz is impossible, I doubt there is a single piece of hardware that supports those speeds.

That being said, increasing the PCI-e bus effectively increases bandwidth on ALL PCI-e lanes. High end videocards do show some improvement. However, since the PCI-e specs state 100MHz, most devices won't like higher clocks and will start to produce errors. With a videocard this could result in artifacts or lockups. However with a storage controller or NIC you could end up with corrupt data. Which you can't fix by putting the clock back afterward.
It is the same thing as overclocking PCI bus, back in the days when the AGP/PCI bus wasn't locked but linked to the FSB. Systems became unstable cause of this. And it of course limits overclocking.

Nvidias linkboost can overclock the PCI-e bus to 125MHz when both the board and card support this. I'm unsure how this affects other PCI-e devices. I'm assuming they somehow got around this. 


Anyway, long story short. Yes it could improve performance slightly. On the other hand it could corrupt data/damage things. When doing such things, make sure you know what is connected to your PCI-e bus.


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## qamulek (Sep 26, 2008)

DanTheBanjoman said:


> First of all, 166MHz is impossible, I doubt there is a single piece of hardware that supports those speeds.
> 
> *That being said, increasing the PCI-e bus effectively increases bandwidth on ALL PCI-e lanes.* High end videocards do show some improvement. However, since the PCI-e specs state 100MHz, most devices won't like higher clocks and will start to produce errors. With a videocard this could result in artifacts or lockups. However with a storage controller or NIC you could end up with corrupt data. Which you can't fix by putting the clock back afterward.
> It is the same thing as overclocking PCI bus, back in the days when the AGP/PCI bus wasn't locked but linked to the FSB. Systems became unstable cause of this. And it of course limits overclocking.
> ...



While reading about 680i/780i threads I remember reading someone saying that 125Mhz for pcie2.0 was standard, and at the time I was having trouble with my videocards being recognized so I went into the bios to check this frequency.  I found two settings for pcie frequency with both of them set to 100Mhz.  I tried one and got a BSOD   I reset cmos then tried the other and everything booted up fine, except for my videocard problem...  At the end I did get the videocard problem fixed, and set the frequency back to 100Mhz.


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## KBD (Sep 26, 2008)

DanTheBanjoman said:


> Nvidias linkboost can overclock the PCI-e bus to 125MHz when both the board and card support this. I'm unsure how this affects other PCI-e devices. I'm assuming they somehow got around this.
> .



Yep, my board has that feature but i still lock it at 100mhz and overclock the card manually. One interesting thing about this board is that i can control the PCI-e bus of both of my x16 slots. So the NB to PCI-e clock controls slot 1 and SB to PCI-e clock controls slot 2. The board also has a PCI-e x8 slot but i'm not sure how that one is being affected as there are no BIOS settings for it, i don't think it was even meant for graphics cards as there was no 3 way SLI then.


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## imperialreign (Sep 26, 2008)

largon said:


> Same BS can be said about _overclocking anything_.



that is very much true  - but was it worth the comment of denouncing it as BS?


Seriously - we don't know the extent of the OPer's knowledge in OCing, and how many novices are aware of that fact I stated?  Like wise, how many of us with a lot of experience tend to overlook simple things like that at this point?


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## 3870x2 (Sep 26, 2008)

largon said:


> Got a link to support that?
> Never heard anything like that.
> Never heard any such stories, either.
> Link?
> ...



There is no reason to be disrespectful, if you have a problem with what i say, i would be glad to talk to you about it, PM me.
No one likes messages like these, in a respectful forum like TPU.
do you have a link to discredit that? if so, please let me know, because i owe you nothing, i dont even know who you are.
respectfully yours, jacob.
EDIT: here, i did a little bit of homework for you all.
http://www.interfacebus.com/Design_Connector_PCI_Express.html
still, this does not make it clear exactly what happens, but because of the fact that you change it and nothing happens to your cards freq, i would say that your card underclocks to keep its speed (because if you change the speed in the bios, the cards clock stays the same in GPU-Z) so naturally, the card would have to underclock to keep its clock setting or it would change.  I figured that from my own sense, all physical proof from what i know about PCI-E and motherboards and my own tests, logically this would happen, the only other way is that if it stays the same clock in windows, nothing actually changed in the bios.


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## largon (Sep 27, 2008)

*3870x2*,
In what way is...


> Got a link to support that?
> Never heard anything like that.


...in any possible way _disrespectful_? 









> There is no reason to be disrespectful, if you have a problem with what i say, i would be glad to talk to you about it, PM me.
> No one likes messages like these, in a respectful forum like TPU.
> do you have a link to discredit that? if so, please let me know, because i owe you nothing, i dont even know who you are.
> respectfully yours, jacob.


Now _that_ is indeed patronising. 


> do you have a link to discredit that?


 
I'll just say this is some rather _twisted thinking_. 


			
				3870x2 said:
			
		

> because of the fact that you change it and nothing happens to your cards freq, i would say that your card underclocks to keep its speed (because if you change the speed in the bios, the cards clock stays the same in GPU-Z) so naturally, the card would have to underclock to keep its clock setting or it would change.


GPU-Z does not display PCIe link frequency. And, PCIe link freq is _not_ tied to GPU core freq. There's a PCIe link controller in the GPU, _that_ is the only part which changing PCIe freq in mobo bios affects.


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