x8-x8 vs. x16-16

[ryder_22]

Is there large performance difference having x16-x16 vs. x8-x8, enough to warrant a MB that is almost double in price?
Wouldn't the negative of Sli on one card be that both cards share a single x16 slot, where as seperate they each have their own x16slot, making for x32 between both?

 

[prozac26]

Is there large performance difference having x16-x16 vs. x8-x8, enough to warrant a MB that is almost double in price?

You won't even notice a difference.

 

[ryder_22]

How would you not notice a difference when its double the bandwidth. Doesn't that mean that the video card has the potential to send double the bits at any given second--double the data at any given second?
There should theoretically be a massive difference. In practice, there may not be if the GPU cannot send more bits than whatever the data transer rate would be for x8. IF the GPu can send data at x16bandwidth, it should be twice the speed of a card that can only send data at x8 bandwidth. why have x16 slots then if cards can't go past x8? maybe dx10 cards will better utilize the slot.

Another question a bit off topic--- is AGP1x the same speed at PCI-E1x?
Is AGP 8x same as PCI-E 8x? Just wondering the relative performance ratios.

 

[prozac26]

Video cards don't use that much bandwith yet. The key word is "can".

 

[cleeve]

How would you not notice a difference when its double the bandwidth.

Because bandwidth to the bus is not the limiting factor when it comes to PC gaming framerates.

Increasing the bus bandwidth in this case is like taking a car from a single lane highway to a double lane highway. It's not going to go any faster; the car's speed isn't limited by how many cars the highway can handle.

 

[prozac26]

Increasing the bus bandwidth in this case is like taking a car from a single lane highway to a double lane highway. It's not going to go any faster; the car's speed isn't limited by how many cars the highway can handle.

lol, nice.

:trophy:

 

[cleeve]

Hey, you picked up an X1900 GT? Congrats dude!

That'll be a helluva jump from your old 9550...

 

[prozac26]

Hey, you picked up an X1900 GT? Congrats dude!

Thanks, still need mobo and RAM (you know already) to complete the new one.

 

[col-p-todd]

I,d say just stick with the 8x mobo and save the rest of the money for another upgrade.

 

[Heyyou27]

The only situation I could see it making any difference at all would be with a Quad SLI system, but even then it may be unnoticable.

 

[elpresidente2075]

Another question a bit off topic--- is AGP1x the same speed at PCI-E1x? Is AGP 8x same as PCI-E 8x? Just wondering the relative performance ratios.

The original AGP standard (AGP 1x) provided a data transfer rate of 264 Mbytes/sec. AGP 2x is 528 Mbytes/sec. AGP 4x is 1 Gbyte/sec. AGP 8x is 2 Gbytes/sec.

Link

First-generation PCIe is often quoted to support a data rate of 250 MB/s (238 MiB/s) in each direction, per lane. This figure is a calculation from the physical signalling rate (2500 Mbaud) divided by the encoding overhead (10bits/byte.) This means a 16 lane (x16) PCIe card would then be theoretically capable of 250 * 16 = 4000 MB/s (3.7 GiB/s) in each direction.

Link

Yes, there is a significant difference between the two.

Edit:
Note that PCI-e's bandwidth is in each direction, and AGP is total.

 

[sojrner]

lol, good find stranger. I remember that one back in the day. The intro seems kinda funny (in a weird way) now w/ the going's on in the world. 2 years seems like forever...

 

[ryder_22]

eVGA E-GEFORCE 7800GTX 256M DDR3 PCI-E
if we take that card for example, and had an exact replica that was AGP8x, you're saying that games would run at the same FPS?
i see what u're saying, if FEAR doesn't transfer over 1GB/s.
When do you predict games will transfer closer to 2gb/s?
Is there any games on the market that transfer greater than 1GB/s of bandwidth? Will Crysis be over 1GB/s?--predication of course.
So for all practical applications, over 1 GB bus isn't required. There must be some instances where 1GB/s of bandwidth does occur?
I guess when quad core,8 core whatever comes into play, 2gb/s or greater will become a reality.
As well, why did they stop making top end AGP cards if games don't require more than 1gb/s of bandwidth?

 

[sojrner]

man, right now PCI-e is just not needed. AGP8x is plenty. PCI-e is just a forward looking interface that allows the ceiling to increase and stay above the need. AGP was hitting the physical limit of the interface design, but nothing was actually saturating it. (yet) It will take a long time for games to fill that 8x PCI-e bandwidth, let alone 16x.

predictions are tough to make for games man. That is a far-away time question... who knows?

 

[NEO3]

I never saw a test specifically on that matter.
It would be really nice to see tom's addressing this subject.

 

[sojrner]

google it up, there are plenty of tests showing that agp8x is still plenty, in fact in many tests it shows agp4x as good enough. That would then translate into PCI-e 8x as more than enough.