performance difference between pci-e 16x and pci-e 2.0

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fantome2024

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I have a mobo that supports pci-e 16x and I know everythings backwards compatible but do we have any idea the performance difference between the two?
 
From what I've heard pcie 2.0 just allows for more power to be drawn through the slot, therefore faster cards, correct me if I'm wrong.
 
I believe the reason for more power is to eliminate the need for external power connectors.. ?
 
kllrnohj said:
It also doubles the bandwidth per lane: http://www.pcisig.com/news_room/faqs/pcie2.0_faq/
Click to expand...

that's correct. haha if ur too lazy to follow the link...
wikipedia said:
PCIe 2.0 doubles the bus standard's bandwidth from 2.5 Gbit/s to 5 Gbit/s, meaning a x32 connector can transfer data at up to 16 GB/s in each direction.

The PCI-SIG also said PCIe 2.0 also features improvements to the point-to-point data transfer protocol and its software architecture.
Click to expand...
 
From what I've read (god I say that a lot), today's cards don't even max out the current 16x PCIe 1.1 bandwidth. So PCie 2.0's doubling of the bandwidth isn't going to translate to any tangible performance gains at all. But if GPU manufacturer's start implementing multi-gpu's on single cards like I've beening reading about for years, the extra bandwidth would become quite beneficial.
 
ok so break it down for me :) does that mean me running it in a 16x port I wont get the same performance as a pci-e 2.0 ?
 
ryan_975 said:
From what I've read (god I say that a lot), today's cards don't even max out the current 16x PCIe 1.1 bandwidth. So PCie 2.0's doubling of the bandwidth isn't going to translate to any tangible performance gains at all. But if GPU manufacturer's start implementing multi-gpu's on single cards like I've beening reading about for years, the extra bandwidth would become quite beneficial.
Click to expand...

If the multi-GPU is on the same PCB, then why would it go over the PCIe bus at all? :confused:

@fantom2024: It means that there aren't any advantages to moving to PCIe 2.0 right now, unless you have a PCIe card that is limited by the bandwidth available (which doesn't include video cards).
 
DaNotoriousDOM said:
I thought that originally, then I read that the cards will have 8 pin power connectors that provide this extra power. The slot itself won't provide the extra power.

http://www.hardforum.com/showpost.php?p=1031542938&postcount=4
Click to expand...

The slot provides double the power, 150w vs 75w currently. But because highend cards use more power than 150w, plus the fact that people will be also using these cards in PCIe 1.1 slots, requires that the necessary power connectors still be available.
 
fantome2024 said:
ok so break it down for me :) does that mean me running it in a 16x port I wont get the same performance as a pci-e 2.0 ?
Click to expand...

Absolutely not. The 8800GT 512 barely uses more than 8x PCI-E 1.0's bandwidth, per tests done. There is approximately a 4% performance loss according to the tests I have seen when using that vs. 16x PCI-E 1.0. That means even those without 16x PCI-E 1.0 SLI boards that only do 8x per card can still get the full benefit from SLI'd GT's, to put it more plainly. A 16x port will run it at 100% speed.

ryan_975 said:
The slot provides double the power, 150w vs 75w currently. But because highend cards use more power than 150w, plus the fact that people will be also using these cards in PCIe 1.1 slots, requires that the necessary power connectors still be available.
Click to expand...

Correct.
 
kllrnohj said:
If the multi-GPU is on the same PCB, then why would it go over the PCIe bus at all? :confused:

<sniip>
Click to expand...

because each GPU will still require a connection to the CPU and main memory to get the information it needs to process. InterGPU communications wouldn't need to go over the PCIe buss though.
 
GoldenTiger said:
fantome2024 said:
ok so break it down for me :) does that mean me running it in a 16x port I won't get the same performance as a pci-e 2.0 ?
Click to expand...
Absolutely. The 8800GT 512 barely uses more than 8x PCI-E 1.0's bandwidth, per tests done. There is approximately a 4% performance loss according to the tests I have seen when using that vs. 16x PCI-E 1.0. That means even those without 16x PCI-E 1.0 SLI boards that only do 8x per card can still get the full benefit from SLI'd GT's, to put it more plainly. A 16x port will run it at 100% speed.
Click to expand...

Careful reading ftl, lol. I believe you meant to disagree with fantome's "won't", not agree with it ;)

@ryan_975: Yes, but hopefully a majority (if not all) of the data it actually needs is in vram, negating the need for such bandwidth. no?
 
kllrnohj said:
Careful reading ftl, lol. I believe you meant to disagree with fantome's "won't", not agree with it ;)

@ryan_975: Yes, but hopefully a majority (if not all) of the data it actually needs is in vram, negating the need for such bandwidth. no?
Click to expand...

not quite. All the textures for the current area would optimally be in VRAM, but if you have large maps and multiple levels then all those textures have to loaded into physical memory then copied over to VRAM. Main memory is also used as an overflow when textures aren't needed just yet, but they still need to be close at hand (compared to being on the drive still). If a card's VRAM was enough for everything then you wouldn't need 2GB of DDR2-800 to improve the perfomance of some games.
 
kllrnohj said:
Careful reading ftl, lol. I believe you meant to disagree with fantome's "won't", not agree with it ;)

@ryan_975: Yes, but hopefully a majority (if not all) of the data it actually needs is in vram, negating the need for such bandwidth. no?
Click to expand...

Good catch, edited my post.
 
GoldenTiger said:
Correct.
Click to expand...

I think thats actually incorrect. The slot itself doesn't provide more power, but they are removing the 6pin (75watt) and using 8pin(150watt) power adapters instead.

1. Summary of the Functional Changes
To redefine the power value interpretation in Slot Capabilities register and Power Budgeting Data
register.
2. Benefits as a Result of the Changes
The existing power limit definition constrains the power limit to a maximum of 255W. This ECR
enables smooth inter-operability with future higher power PCI Express products (e.g. graphics
processor), which might consume more than 255W.
3. Assessment of the Impact
No impact to existing PCI Express products as cards with bigger than 240W power consumption
do not exist today.
4. Analysis of the Hardware Implications
No impact to existing hardware.
5. Analysis of the Software Implications
No impact to existing software. Future software
Click to expand...

From a PDF from their website

and the quote from Bit-Tech
When it was designed, PCIe was supposed to be a real futureproofing - 75W of power and 2.5Gbps of bandwidth (a 16x card could pull nearly 8Gbps) right through the slot. This eliminated the need for external power and greatly exceeding AGP's not even half-used bandwidth constraint. Of course, the latest cards (such as the NVIDIA 8800 GTX) are already on their second independent power connector, drawing a whopping 185W of power.

In order to compensate, PCIe 2.0 has modified the power standard. The previous 6-pin 75W connector has now been retired, moved instead to an 8-pin 150W connector (see the Inquirer for a picture). Bus speeds have also increased to 5Gbps, meaning that a 16x card can now potentially pull up to 16Gbps. Of course, current cards are a long way from even maxing out the PCIe 1.1 interface, so this is much more of a theoretical improvement.
Click to expand...
 
jmackay said:
I think thats actually incorrect. The slot itself doesn't provide more power, but they are removing the 6pin (75watt) and using 8pin(150watt) power adapters instead.



From a PDF from their website

and the quote from Bit-Tech
Click to expand...

they've done both. PCIe 8pin and slot power double the current standard.

http://www.pcisig.com/news_room/faqs/pcie2.0_faq/

Q6: What other new features are introduced in the PCIe 2.0 specification?
A6: The most predominant new feature in PCIe 2.0 is 5GT/s speed, which includes new mechanisms for software control of link speed, reporting of speed and width changes, and control of loopback. Other new features include:

PCI compatibility using the established PCI software programming models, thus facilitating a smooth transition to new hardware while allowing software to evolve to take advantage of PCI Express features
Enhanced Completion Timeout Control, which includes required and optional aspects, reduces false timeouts and increases the ability to &#8216;tune&#8217; the timeouts
Function Level Reset and Access Control Services, giving enhanced robustness and support of certain IOV features (optional)
Slot Power Limit Changes to allow for higher powered slots, which support the newer, high-performance graphics cards. This new feature works in tandem with the 300W Card Electro-mechanical specification
Speed Signaling Controls to enable software to determine whether a device can operate at a specific signaling rate, which can be used to reduce power consumption, as well as provide gross level I/O to memory
Click to expand...
 
ryan_975 said:
they've done both. PCIe 8pin and slot power double the current standard.
Click to expand...

Is there a source stating that the slot will provide more power? It sounds like it will just allow for more, not provide any extra.
 
Any pictures of the 8800GT and it's connector? Is it 8pin? Do they provide adapters since no PS has 8pin PCIe connectors yet.

I feel like my almost build PC is already outdated. I got a nice Antec Trio 650W and it has dual 6pin PCIe connectors.
 
DaNotoriousDOM said:
Any pictures of the 8800GT and it's connector? Is it 8pin? Do they provide adapters since no PS has 8pin PCIe connectors yet.

I feel like my almost build PC is already outdated. I got a nice Antec Trio 650W and it has dual 6pin PCIe connectors.
Click to expand...

You're seriously joking right?

1x 8pin PCIe = 11
http://www.newegg.com/Product/Produ...&Subcategory=58&description=&Ntk=&srchInDesc=

2x 8pin PCIe = 42
http://www.newegg.com/Product/Produ...&Subcategory=58&description=&Ntk=&srchInDesc=

4x 8pin PCIe = 1
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139006


But to answer your question the 8800GT has only a single 6pin PCIe connector. http://www.newegg.com/Product/ShowImage.aspx?Image=14-127-311-07.jpg
 
DaNotoriousDOM said:
Any pictures of the 8800GT and it's connector? Is it 8pin? Do they provide adapters since no PS has 8pin PCIe connectors yet.

I feel like my almost build PC is already outdated. I got a nice Antec Trio 650W and it has dual 6pin PCIe connectors.
Click to expand...

My CoolerMaster 850watt has 4x 6pin and 4x 8pin.

I think there are other PSU's that have at least 2x 8pin also...
 
Battl3fr0nt said:
My CoolerMaster 850watt has 4x 6pin and 4x 8pin.

I think there are other PSU's that have at least 2x 8pin also...
Click to expand...

That sucks. I hope I can use my 6pin PCIe connectors for a while more. If I knew about that PCIe2.0 8pin connector I would have bought a different PS.
 
DaNotoriousDOM said:
That sucks. I hope I can use my 6pin PCIe connectors for a while more. If I knew about that PCIe2.0 8pin connector I would have bought a different PS.
Click to expand...

You can use 6pin connectors with an 8pin card. There's just some limitations, like not being able to overclock on the HD2900's
 
I forgot where, but I read that when talking to AMD/ATI engineers, they stated that on pcie1.1 , top end cards were pulling 8-900mbps, but when using pcie 2.0 it almost hit the 2.0 limit(5gbps) maybe someone can chime in and link to that discussion :p
 
nevermind. :)

Yeah, technology advances fast. Hope I don't have to replace the power supply too soon :)
 
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