# P45 vs x38/x48 for Crossfire



## ViciousXUSMC (Jul 4, 2008)

I just built my new computer, and I feel I made a great build and all the right choices until just the other day I found one piece of information that really sort of upset me and gave me that ikky feeling in my stomach.

Based on this article:  http://www.tweaktown.com/articles/1472/intel_p45_vs_x48_crossfire_performance/index.html

There are pretty much saying that due to the x8/x8 split for crossfire on the P45 it has a pretty big disadvantage compared to the x38/x48 chipsets with full x16/x16.  

I built my entire system around the idea of that great sale for the 4850's at my local best buy only 150$ each so 300$ for the pair.  I also loved the P35 chipset so figured P45 was a perfect choice and thus what I went with. (I normally do not even fathom the idea of dual card setups but this was a good exception)

I am just looking for confirmation that this article is correct from other experts because I cant see it being right.  Maybe the numbers are true, but I feel its not due to the bandwidth of the pci-e slots and it has to be something else.


Sorry for the long thread but let me explain.

First of all I have done various testing in the past to determine when a slot will bottleneck a card because there is very little information that I can find on the net to determine this.  I found that in my bosses computer with a P35 chipset and a 9600gt I was able to get about 3000pt in 3dmark06 with a 2x PCE-E 1.0 slot, and then increasing that to a 4x slot I got just short of 10,000 points.  That shows a ton of bandwidth from just 2x to 4x.  And that was 1.0 spec and its doubled for 2.0 spec.

So I cant reasonably conceive how a 8x 2.0 slot will hold back a 4850 as 8x 2.0 is 4x faster than that 10,000 mark.  I know thats not a valid comparison since 3dmark06 is synthetic and also nearly half of it is cpu score, but I am leaving alot of room for error when a 4850 scores like 13,000 stock and it has room for "40,000" in a 8x slot.

The next common sense idea is that all the dual gpu core cards like the 9800GX2 or soon to be 4870X2 they are basically two cards together in one, and currently the fastest single slot is 16x.  Thats basically allowing the bandwidth of that one card to be the same as splitting it into two cards each with 8x.  I have not heard anything about a 16x slot getting even close to bottlenecking one of those cards.

Still tho with all that known I wont rest easy until I know for sure I made a mistake going with P45 or not.  Since my goal was to finally have a high end setup that can play all my games at full 1080p, if that article is correct I really screwed up.

Here is my build: http://forum.desktopreview.com/showthread.php?t=234528

In short:
Q6600 @ 3.6ghz
4gb DDR2 @ 800mhz
2x 4850 675/1000
3dmark06 18,500

Its doing great for grid, CoD4, and even Crysis (well not so much Crysis I am getting artifacts of sorts supposedly crossfire related) but that extra 4 or 5 fps would really help in Crysis, but I dont know if I would be willing to sell and rebuild with a new mobo.


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## aCid888* (Jul 4, 2008)

The P45 is a solid chipset same as the P35, it wont make a whole lot of difference to your gaming experience/fps to only have 8x instead of 16x.

Bottom Line: don't worry


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## MoA (Jul 4, 2008)

if you want to do CF

DEFINITELY go for a X38/x48
many tests showed that x16/x16 is much faster than x8/x8
(http://www.tweaktown.com/articles/1472/7/intel_p45_vs_x48_crossfire_performance/index.html)

and it's not weaker in any aspect for overclocking compared to P35/P45


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## Xaser04 (Jul 4, 2008)

MoA said:


> many tests showed that x16/x16 is much faster than x8/x8
> (http://www.tweaktown.com/articles/1472/7/intel_p45_vs_x48_crossfire_performance/index.html)



These many tests you refer to, are they just the tweaktown review?


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## MoA (Jul 4, 2008)

Xaser04 said:


> These many tests you refer to, are they just the tweaktown review?



I guess there are bored people, who just posts to get attention lol or to hassle other people :shadedshu

another test provided by google:

http://www.tomshardware.com/de/Graf...16-x8-x4-Crossfire,testberichte-239907-4.html

http://media.bestofmicro.com/D/P/71773/original/Crossfire-Einzelergebnisse-x8-vs-x16.jpg


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## InnocentCriminal (Jul 4, 2008)

MoA said:


> I guess there are bored people, who just posts to get attention lol or to hassle other people :shadedshu



They don't even read the original post most of the time. ViciousXUSMC, you may find this review of the ASUS P5Q interesting, they compare it against these boards...

# Gigabyte GA-X48T-DQ6 (Intel *X48*, DDR3, F4 BIOS)
# Abit IX38 QuadGT (Intel *X38*, DDR2, "12" BIOS)
# Gigabyte GA-EP35-DS4 (Intel *P35*, DDR2, F3 BIOS)
# MSI P35 Diamond (Intel P35, DDR3, 2.2 BIOS) 

What P45 board did you buy exactly? Hope it helps! Welcome to the forums btw.


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## Xaser04 (Jul 4, 2008)

MoA said:


> I guess there are bored people, who just posts to get attention lol or to hassle other people :shadedshu
> 
> another test provided by google:
> 
> ...



I was asknig you a question and instead of responding in a civilised manner you accuse me of posting to get attention or trying to give you hassle?! What are you harping on about?

Why didn't you also link to these additional tests in your first post?!

EDIT: God that TH review is hard to read with just tables of numbers. 

As for the P45 CF issue a quick look on bit-tech shows that in CF (dual HD3870) the P45 boards are performing identically to the X38/X48 boards. 

http://www.bit-tech.net/hardware/2008/06/20/msi-p45-platinum/12

(This reviews lists all of the P45 boards in the results). 

It clearly shows that there is no perfomance drop from 16x16x to 8x8x. 

This calls into question the validity of the tweaktown review (given that they also only tested one motherboard as well it doesn't help matters).


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## Darknova (Jul 4, 2008)

Ok, firstly, MoA, I would like to point out that that review is borked big-style. Either I'm reading it wrong, or Call of Duty 4 is getting 700+ FPS, I've yet to see a card in the entire world that can do 700 FPS on CoD4 even at minimum settings.

And also, notice how the others are all within a few fps of each other? I think the biggest is about 9fps, honestly, that's not much when we are talking 80+ fps.

Second, that bit-tech review threw up something interesting, the P5Q performing better in CF then the rest? Hmm...


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## ViciousXUSMC (Jul 4, 2008)

Well I am very skeptical of that tweak town review, like I said it sort of defies what I have seen in my own testing, and even in there test results there is data that doesn't make too much sense.  Heck I didnt see it myself but somebody posted on another forum about that article that originally they put nvidia drivers under the "test setup" section rather than the catalyst drivers....

I will go and read the links you guys have posted now and see if information from alternat sources seems to be consistently showing the same.

As for my board?  Its the Asus P5Q Deluxe, my entire computer build is in the link I posted above.

edit: first link read the toms hardware one.  It scared me at first confirming what tweaktown had but if you pay attention you will notice that the test was 8x/8x @ 1.0 spec vs 16x/16x 2.0 spec.  In my case with a P45 being 2.0 spec it would have double the bandwidth of what they had in that test.

edit2: second link is the same 8x/8x 1.0 spec vs 16x/16x 2.0 spec I can definitly see a 4850 being slowed down in a 8x 1.0 slot...  so I agree with those links.  but with 2.0 spec and 8x lane is just as fast as an older 16x lane so I really cant image it being an issue.  So the quest continues to verify these tweak town numbers.


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## InnocentCriminal (Jul 4, 2008)

^^

Hit the nail on the head with my link then. 



You should fill out your system specification if your User Control Panel.


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## ViciousXUSMC (Jul 4, 2008)

InnocentCriminal said:


> ^^
> 
> Hit the nail on the head with my link then.
> 
> ...



Done


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## InnocentCriminal (Jul 4, 2008)

Good man!

XD


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## mk_ln (Jul 4, 2008)

the only issue i have with the bit-tech review is that it was using older cards not capable of saturating the bandwidth. supposedly these new cards ARE capable of doing that, but like ViciousXUSMC, i am skeptical about tweaktown's pcie performance review


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## MoA (Jul 4, 2008)

yeah very strange bit-tech and tweaktown..
maybe both use different drivers, since there seems to be a big difference between:8.6 normal, 8.6 hotfix, 8.6 beta, 8.7 beta...

but tweaktown is using 4850 as tests which may request much more bandwith from the pciE especially with those 800SP, this is may be where the x16 and x8 shows the differences (maybe...)


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## InnocentCriminal (Jul 4, 2008)

The Bit-Tech review is relatively old compared to the TweakTown.


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## dark2099 (Jul 4, 2008)

From fitseries3 experience, running a 3870x2 on a PCI-E 1.x 4x lane didn't seem to affect performance too much, so where as yes with crossfire in dual PCI-E 2.0 16x compared to the 8x, you do technically have double the speed, I'm hesitant to believe that it makes too much of a difference, maybe with the newer 4870 and coming 4870x2, but for the 4850 and lower, probably not as much.


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## InnocentCriminal (Jul 4, 2008)

Thinking of it, I doubt many cards actually utilise the PCIe bus to it's fullest. It probably just gives the cards more headroom if they ever needed. I don't even think the AGP bus is fully utilised now, even with a HD3850.


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## HTC (Jul 4, 2008)

Someone please correct me if i'm wrong but i think that the x8 VS x16 only comes into play with high resolutions and very high details: i'm talking 1920 / 1200 and bigger resolutions.

The reason this is so, is because the x8 bandwidth isn't fully utilized @ lower resolutions but it starts to reach it's peak @ 1920 / 1200 *with* high details, and it becomes bottlenecked.


I remember reading about this, a while back (don't recall from where), and this is what i understood of it.


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## allen337 (Jul 4, 2008)

Ive done extensive testing on 2-2900xts and x38-975x-p35 chipsets in crossfire- 2-4 fps in crysis difference in all 3 chipsets The single card solution is the best, crossfire at best gives 30-35% increase on second card but the card isnt 65-70% off price. Dual gpu seems to do the best for now.  ALLEN


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## ViciousXUSMC (Jul 5, 2008)

I agree allen337 for the most part, but I only decided to get 2 of them because of the great deal I got.  25% off all visontek cards at bestbuy means they costed 150$ each so 300$ for the pair and I knew that 2 4850's would beat a single 4870.


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## jmke (Jul 16, 2008)

sorry for the bump but this issue needs addressing, the findings by TweakTown are far from final or conclusive; Legionhardware did their own tests and the difference between P45 <> X48 is 5% in best case scenario.


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## Tatty_One (Jul 16, 2008)

For all I have read (and thats a lot) on tests using modern cards (3850/3870 onwards) 8 x 8 across the board is only a minor 5% decrease in performance against 16 x 16 and very much better than say the P35 at 16 x 4 which seems to sit around at 15% hit, sometimes more.  Just set the PCI-E bandwidth from 100 to 110mhz and that makes up for the 5% straight away!


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## Ketxxx (Jul 16, 2008)

The article is right and wrong. Some stay steadfast in the belife that 16x CF on PCIE is better than 8x CF on PCIE 2.0. The reality is PCIE 2.0 offers advantages over PCIE. PCIE 2.0 in 8x CF offers the same bandwidth as PCIE @ 16x CF, while PCIE 2.0 also offers more power via the slot (125w I belive over 75w on PCIE) as well as having various subroutine and packet optimisations PCIE does not have. So, in summary PCIE 2.0 has over PCIE;

PCIE 2.0 has the same bandwidth @ 8x as PCIE has @ 16x
PCIE 2.0 offers more power via the slot than PCIE does
PCIE 2.0 has various subroutine and packet optimisations PCIE does NOT have.

So, is PCIE 2.0 beter than PCIE even when on a P45 PCIE 2.0 runs @ 8x in CF and on an X38\48 the PCIE runs @ 16x in CF? Yes. Due to the above mentioned, 8x CF on PCIE 2.0 at least makes it equal to PCIE x16 in terms of bandwidth, and in other areas PCIE 2.0 is noticably superior on a subroutine level.


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## Jansku07 (Jul 16, 2008)

Look @ this. X48 vs x38 vs p45 vs p35. Testsetup: Hd4850CF + Q6600 @ 3,0 gHz. http://www.legionhardware.com/document.php?id=761&p=0


			
				part of the conclusion said:
			
		

> ... For the most part the X48 is just 5% faster than the cheaper P45 chipset, while this chipset held roughly the same margin over the older X38 chipset. Therefore as we see it, X38 owners really would need to purchase an X48 motherboard to see any real performance gains, while the P45 is a massive step up from the P35 chipset when talking Crossfire performance.


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## Ketxxx (Jul 16, 2008)

Thats talking about the P45. I was specifically comparing PCIE vs. PCIE 2.0, clearly 2.0 is superior. Any performance deficite the P45 currently has can easily be put down to immature chipset drivers and the BIOS needing slight refinement. Hell, theres only been one driver Intel has churned out for the P45 currently its that new and you get an unknown error while trying to install the P45 chipset drivers, you have to run it again to install everything, and who knows if that unknown error is overcome the 2nd time around or if that particular part of the driver is still bugged.


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## Jansku07 (Jul 16, 2008)

> Thats talking about the P45. I was specifically comparing PCIE vs. PCIE 2.0, clearly 2.0 is superior.


 I didn't put that link up to answer you, but to make a point about p45 vs X38/x48 performance differencies. PCIE 2.0 is ~ 2x faster than PCIE 1.0, your right.


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## Tatty_One (Jul 16, 2008)

Jansku07 said:


> I didn't put that link up to answer you, but to make a point about p45 vs X38/x48 performance differencies. PCIE 2.0 is ~ 2x faster than PCIE 1.0, your right.



But not 2x faster than PCI-E 1.1 and faster is relative, it's not actually faster if the card cannot use the extra bandwidth/throughput that 2.0 has to offer.............and they dont.....yet, to put things in perspective, the first card that used all of the bandwidth of AGP 8x, even though it was on PCI-E was the 8800GTX if you get my meaning.....if it's not there, it cant be used, in fact some call PCI-E 2.0 a gimmick! (not me though!).

Strictly speaking there are advantages of course like the added throughput availability for slots less than 16x as Ket mentioned.

thats all as I understand it from what I have read although I may have got some of it wrong.


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## ghost101 (Jul 16, 2008)

Jansku07 said:


> Look @ this. X48 vs x38 vs p45 vs p35. Testsetup: Hd4850CF + Q6600 @ 3,0 gHz. http://www.legionhardware.com/document.php?id=761&p=0



p45 > x38. That mixes things up. That review does avoid 2560*1600 though, which was the main resolution tweaktown showed a major difference between the p45 adn x48 in.


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## ViciousXUSMC (Jul 17, 2008)

Yeah I would like to see some very intensive ultra high resolution stuff to put this myth down for good.  But its looking more and more like tweak towns little review is fubar.


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## Mussels (Jul 17, 2008)

P35 = 16x/4x in 1.0
P45 = 8x/8x in 2.0

if you use 2.0 cards, the P45 will, be a winner as its equal to two 16x slots on 1.0


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## Tatty_One (Jul 17, 2008)

Mussels said:


> P35 = 16x/4x in 1.*1*
> P45 = 8x/8x in 2.0
> 
> if you use 2.0 cards, the P45 will, be a winner as its equal to two 16x slots on 1.0



Amended   Therefore 8 x in 2.0 is NOT equal to 16 x in 1.0, it's more than double but see my post below... contrary to what seems to be popular belief.


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## Mussels (Jul 17, 2008)

whats teh diff between 1.0 and 1.1? and what the heck do i have :-S


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## Tatty_One (Jul 17, 2008)

Mussels said:


> whats teh diff between 1.0 and 1.1? and what the heck do i have :-S



Lol that was quick!

1.0 = 2Gbit
1.1 = 2.5Gbit
2.0 = 5gbit

I think thats the way it goes.

You have 2.5gbit @ 1.1 I beleive.


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## Tatty_One (Jul 17, 2008)

Sorry, I didnt word that particularily well, my point a few posts ago is that whilst the throughput is available in 2.0, if the card cannot use it then it's worthless, 2 cards have 2 slots and therefore 2 throughputs so technically that dont change things, think of 780i, only one slot was 2.0, the other being 1.1 but I am willing to bet on a pair of 8800GT's in  each slot for example would be using only about 2Gbit throughput on each.....if that.....that's as I understand it......is that clearer cause even I'm confused now!


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## Hayder_Master (Jul 17, 2008)

first we must say pci-e x16 2.0 , p45 don't come with dual 16x 2.0 , x38 have it and x48 sure , but we can say as other friend say before the x48 is extreme x38 in overclock and fsb


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## Hayder_Master (Jul 17, 2008)

Tatty_One said:


> Lol that was quick!
> 
> 1.0 = 2Gbit
> 1.1 = 2.5Gbit
> ...




also with overclock we can say
1.0 up to 2.5gbit
1.1 up to 4gbit
2.0 up to 5gbit or read something not sure for it you can reach 6gbit with 2.0


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## Tatty_One (Jul 17, 2008)

hayder.master said:


> also with overclock we can say
> 1.0 up to 2.5gbit
> 1.1 up to 4gbit
> 2.0 up to 5gbit or read something not sure for it you can reach 6gbit with 2.0



No, overclocking a card does not increase the slots throughput, the cards throughput yes but in your example, 1.0 cannot be higher than 2GBit cause thats all there is if you get my meaning, and overclocking does not have that big an impact, a 4870 overclocked does not use the full throughput of 1.1 which was my origional point, I would guess (and thats all it is) that it would probably use around 2 or 2.1Gbit, I do only base that on guesswork and I might be wrong, but working on what I know......an 8800GTX used only about 1.2Gbit throughput (just slightly more than AGP 8x had to offer)......I dont profess to be an expert but from what I have read this seems to be the general idea.


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## Darknova (Jul 17, 2008)

Tatty_One said:


> No, overclocking a card does not increase the slots throughput, the cards throughput yes but in your example, 1.0 cannot be higher than 2GBit cause thats all there is if you get my meaning, and ovewrclocking does not have that big an impact, a 4870 overclocked does not use the full throughput of 1.1 which was my origional point, I would guess (and thats all it is) that it would probably use around 2 or 2.1Gbit.



Although, he could be talking about OC'ing the PCI-E slot directly. That surely would have a difference on bandwidth and throughput?


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## Mussels (Jul 17, 2008)

he might be talking about increasing the PCI-E frequency. Its considered dangerous to go above 115 however.

edit: dark beat me.


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## Darknova (Jul 17, 2008)

Mussels said:


> he might be talking about increasing the PCI-E frequency. Its considered dangerous to go above 115 however.



Depends on the chipset. Back with the old 7800GTX, a certain feature on nforce boards ramped the PCI-E freq up to 125Mhz.


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## Mussels (Jul 17, 2008)

Darknova said:


> Depends on the chipset. Back with the old 7800GTX, a certain feature on nforce boards ramped the PCI-E freq up to 125Mhz.



true. but randomly raising it can do some very nasty things to PCI and PCI-E devices other than the video card.

on MOST systems, PCI and PCI-E are linked. 100MHz PCI-E = 33.3Mhz PCI, everyone is happy. raise it to 125 and you're around 40MHz on the PCI, and some sata/IDE controllers spaz out and corrupt your drives.


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## Darknova (Jul 17, 2008)

Mussels said:


> true. but randomly raising it can do some very nasty things to PCI and PCI-E devices other than the video card.
> 
> on MOST systems, PCI and PCI-E are linked. 100MHz PCI-E = 33.3Mhz PCI, everyone is happy. raise it to 125 and you're around 40MHz on the PCI, and some sata/IDE controllers spaz out and corrupt your drives.



I know that, but I'm sure the features on those boards would lock the PCI link too.

I know I can do that, that's why I've raised my PCI-E link to 110Mhz.


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## Tatty_One (Jul 17, 2008)

Darknova said:


> Although, he could be talking about OC'ing the PCI-E slot directly. That surely would have a difference on bandwidth and throughput?



Bandwidth yes, throughput no I beleive, next you will ask whats the difference I guess?


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## Mussels (Jul 17, 2008)

Darknova said:


> I know that, but I'm sure the features on those boards would lock the PCI link too.
> 
> I know I can do that, that's why I've raised my PCI-E link to 110Mhz.



most of the time the lock is linked to the PCI-E freq. those boarsd that raised it to 125 for nvidia were designed to do it (so there'd be a different divider in use) but for most people it is a bad idea.


The 1.0/1.1 thing does make sense to me at least now, we had a motherboard that was stuck at PCI-E 4x and an 8600GT ran terribly in it, yet it worked fine on another board at 4x. Most likely the first board was a 1.0 board and the second a 1.1.


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## Darknova (Jul 17, 2008)

Tatty_One said:


> Bandwidth yes, throughput no I beleive, next you will ask whats the difference I guess?



No no, I understand that. I just would have thought that by increasing the frequency both would have been affected.


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## Hayder_Master (Jul 17, 2008)

Tatty_One said:


> No, overclocking a card does not increase the slots throughput, the cards throughput yes but in your example, 1.0 cannot be higher than 2GBit cause thats all there is if you get my meaning, and overclocking does not have that big an impact, a 4870 overclocked does not use the full throughput of 1.1 which was my origional point, I would guess (and thats all it is) that it would probably use around 2 or 2.1Gbit, I do only base that on guesswork and I might be wrong, but working on what I know......an 8800GTX used only about 1.2Gbit throughput (just slightly more than AGP 8x had to offer)......I dont profess to be an expert but from what I have read this seems to be the general idea.





i got it , you right my friend i got what you mean , but i think better if he chose 2.0 maybe good help for next upgrade if try the 4870x2 , with this i think he need more bandwidth , but as you say you absolutely right and for this he can take the p45, and i prefer the gigabyte p45


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## Darknova (Jul 17, 2008)

Mussels said:


> most of the time the lock is linked to the PCI-E freq. those boarsd that raised it to 125 for nvidia were designed to do it (so there'd be a different divider in use) but for most people it is a bad idea.
> 
> 
> The 1.0/1.1 thing does make sense to me at least now, we had a motherboard that was stuck at PCI-E 4x and an 8600GT ran terribly in it, yet it worked fine on another board at 4x. Most likely the first board was a 1.0 board and the second a 1.1.



The lock on my board is absolute. I get options as to what speed I want my PCI link to be. From 30Mhz all the way to 40Mhz lol.


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## Mussels (Jul 17, 2008)

well dark, your board is one of the rare ones. enjoy your PCI-E OC'ing  (of course, if your SATA controllers are on PCI-E, you'll still have the same problems)


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## Darknova (Jul 17, 2008)

Mussels said:


> well dark, your board is one of the rare ones. enjoy your PCI-E OC'ing  (of course, if your SATA controllers are on PCI-E, you'll still have the same problems)



Lol, I never go over 110Mhz anyway, it just doesn't show any performance improvement.


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## Tatty_One (Jul 17, 2008)

Darknova said:


> No no, I understand that. I just would have thought that by increasing the frequency both would have been affected.



I think the bandwidth is the speed it gets the info to the "bus" from the GPU, once it's there then throughput takes over but as I said, I really am no expert, I just read a lot when PCI-E 2.0 came out because there was a lot of conflicting talk on the subject.


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## Darknova (Jul 17, 2008)

Tatty_One said:


> I think the bandwidth is the speed it gets the info to the "bus" from the GPU, once it's there then throughput takes over but as I said, I really am no expert, I just read a lot when PCI-E 2.0 came out because there was a lot of conflicting talk on the subject.



None of us are experts, we just get what we can from what we read.

I wonder...Bandwidth is the width of the link right? (IE the bigger the width, the faster everything gets onto the link), so maybe throughput is the actual speed the link goes once everything has gotten onto the link?


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## Hayder_Master (Jul 17, 2008)

So what is this thing called PCIe Frequency?  This is the bandwidth lane between the PCI Express Slot and the Northbridge of the motherboard.  The current PCIe1.0 Standard is 500 MB/s in each direction.  This gives you a total of 8 GB/s on a 16x PCIe Slot.  Assuming you are using the standard 100 MHz PCIe Frequency increasing this by 15% to 115 MHz can give you 9.2 GB/s bandwidth.  It is recommended not to OC this past 120 MHz as it can cause SATA Corruption.  PCIe2.0 doubles this to 16 GB/s in a 16x lane.  There is not a card that currently maxes out the PCIe1.0 bandwidth, however when there is increasing your PCIe Frequency may let you enjoy a new graphics card without having to fork out for a new motherboard.


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## Ketxxx (Jul 17, 2008)

Tatty_One said:


> Sorry, I didnt word that particularily well, my point a few posts ago is that whilst the throughput is available in 2.0, if the card cannot use it then it's worthless, 2 cards have 2 slots and therefore 2 throughputs so technically that dont change things, think of 780i, only one slot was 2.0, the other being 1.1 but I am willing to bet on a pair of 8800GT's in  each slot for example would be using only about 2Gbit throughput on each.....if that.....that's as I understand it......is that clearer cause even I'm confused now!



lol, your basically on the money. Maybe a good way to explain things is with this example;

Say you have a X1950XTX, this, naturally has been designed to work on PCIE and not PCIE 2.0, so putting that X1950XTX in a PCIE 2.0 slot will neither gain you performance or overclockability.

However..

Lets say you have a HD3870, 4850 or something similar. Placing either of these cards in a PCIE slot, even if it runs @ 16x, puts the card at a disadvantage. Why? unlike the X1950XTX the HD series does not natively support PCIE, the 3870\4850 revert to a backward compatibility mode, which more than likely means out of sync packet sizes, increased latencies, and of course less power for the card on the PCIE bus (which to an extent likely means the card is slightly power starved) and so on. These things combined drag a PCIE 2.0 card down. Place these PCIE 2.0 cards into a PCIE 2.0 slot though, 8 or 16x, and their no longer crippled. Optimal packet sizes are sent and recieved, the card is no longer power starved and latencies return to normal meaning no data clogging any PCIE lanes where the bus isn't fast enough (something which would be happening in a PCIE bus). Of course, its also worth remembering that even @ 8x PCIE 2.0 also has the same bandwidth (more or less) of PCIE @ 16x. The unused bandwidth deffinately isn't anything magical, but the headroom certainly does do wonders in the situations where a lot of data is being processed by the system and passed through the PCIE 2.0 lanes. A great example of this is Crysis, with advanced configuration settings you can tell crysis to use the CPU and memory subsystem for processing physics calculations while the GPU just handles all the pretty stuff (and on suitably powerful systems doing this is probably a good idea so as to not overload the PCIE lanes and cause bus saturation) or you can enable the GPU to do the physics if playing on lower quality settings.

Hope that helps ya out Tatty!


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