[xbitlabs] ATI Eliminates Multi-GPU Performance Boosting Technology from Latest Chips

3183 Views 34 Replies 20 Participants Last post by Brutuz, Nov 30, 2009

rico2001

Discussion Starter · Nov 28, 2009

Quote:

ATI Eliminates Multi-GPU Performance Boosting Technology from Latest Chips.

Sideport Not Present in ATI Radeon HD 5000 GPUs â€" Company

ATI, graphics business unit of Advanced Micro Devices, said that it had not implemented its Sideport technology, which was supposed to boost multi-GPU performance of ATI Radeon HD 4800 X2 graphics card, into the new ATI Radeon HD 5800-series graphics processing units (GPUs).

â€œATI CrossFire Sideport is not implemented in the ATI Radeon HD 5800 series GPUs. Improvements in our ATI CrossFireX drivers and interconnect performance have made this feature unnecessary for achieving good performance scaling on multi-GPU boards, be it past generation or current generation products. We have seen that PCI Express 2.1 bandwidth can keep ATI Radeon 5800 GPUs fed with data,â€ said Devon Nekechuk, a spokesperson for ATI.

Back in mid-2008, when ATI introduced its Radeon HD 4870 X2 graphics card powered by two Radeon HD 4870 graphics processing units, it unveiled Sideport technology, which was supposed to boost bandwidth between GPUs in order to...

Source

"Eliminates" is a strong word, more like choosing not to enable the feature. It would not boost performance, it would prevent any bottlenecking of the pci-e bandwidth throughput. Sideport still not needed and I imagine may never be enabled since pci-e 3.0 is in the near future. But who knows... Ati may be saving the sideport for some triple gpu card down the road.

1 - 20 of 35 Posts

Shadow_UGZ

· #2 · Nov 28, 2009

Quote:

Originally Posted by rico2001

View Post

Source

"Eliminates" is a strong word, more like choosing not to enable the feature. It would not boost performance, it would prevent any bottlenecking of the pci-e bandwidth throughput. Sideport still not needed and I imagine may never be enabled since pci-e 3.0 is in the near future. But who knows... Ati may be saving the sideport for some triple gpu card down the road.

Actually it was implemented in the 4870 X2 and 4850 X2 but never used. By eliminating they mean they did not implement it at all in the 5970.

See less See more

adadk

· #3 · Nov 28, 2009

It would still be nice for them to enable it for us 4870X2 owners just for comparisons' sake.

rico2001

Discussion Starter · #4 · Nov 28, 2009

Quote:

Originally Posted by Shadow_UGZ

View Post

Actually it was implemented in the 4870 X2 and 4850 X2 but never used. By eliminating they mean they did not implement it at all in the 5970.

Agreed, not physically on the 5970, although the tech still exist and was on both 4800 X2 cards.

See less See more

rico2001

Discussion Starter · #5 · Nov 28, 2009

Quote:

Originally Posted by adadk

View Post

It would still be nice for them to enable it for us 4870X2 owners just for comparisons' sake.

Not needed. The 4870 X2 only sees a ~11% decrease in performance (in some game titles) with pci-e 2.0 8X so it doesn't come close to the capacity of 16X. There would be no improvement if sideport was enabled.

See less See more

DesertRat

· #6 · Nov 28, 2009

Basically an excuse for saying they could never get it to work right. *sigh*

sLowEnd

· #7 · Nov 28, 2009

Quote:

Originally Posted by DesertRat

View Post

Basically an excuse for saying they could never get it to work right. *sigh*

Their reasoning was Sideport provided very little performance boost for the extra power consumption and heat it entailed.

If the extra power consumption and heat added was unreasonable for the 4870X2, I can see why they omitted it on the 5970 too.

See less See more

XFreeRollerX

· #8 · Nov 28, 2009

If they sell watercooled versions of said waterblocks, you'd think heat isn't going to be a problem...

SO WHY NOT ENABLE IT?

Sideport=joke

darksideleader

· #9 · Nov 28, 2009

Quote:

Originally Posted by sLowEnd

View Post

Their reasoning was Sideport provided very little performance boost for the extra power consumption and heat it entailed.

If the extra power consumption and heat added was unreasonable for the 4870X2, I can see why they omitted it on the 5970 too.

Yes but ATI put a newer suped up version of the plx chip on the 5970, did they not?

So before it was like "Don't worry, sideport, sideport is gonna super charge your card, eventually." And now its like "lets pretend sideport never existed"

See less See more

Cheetos316

· #10 · Nov 28, 2009

Well... considering how we've all been told that it was due to power consumption issues and maybe other issues that we're not aware of and how HD5000's die size is a bit bigger than the ideal size, eliminating Sideport isn't a completely wild idea.

Oupavoc

· #11 · Nov 28, 2009

Well imo it wasnt needed and thus they removed it maybe to save on cost? Just look how the 4870X2 was a beast of a card even without it

See less See more

Shadow_UGZ

· #12 · Nov 28, 2009

Quote:

Originally Posted by XFreeRollerX

View Post

If they sell watercooled versions of said waterblocks, you'd think heat isn't going to be a problem...

SO WHY NOT ENABLE IT?

Sideport=joke

Even if you could control the extra heat, why would you enable it if it had nothing to gain from it? Same reason they didn't use a 512bit bus for GDDR5.

See less See more

DesertRat

· #13 · Nov 28, 2009

Quote:

Originally Posted by Shadow_UGZ

View Post

Even if you could control the extra heat, why would you enable it if it had nothing to gain from it? Same reason they didn't use a 512bit bus for GDDR5.

I believe ATI said it wasn't worth it. IIRC there is a performance increase, but it's not worth the extra power and heat.

You think that'd bother us enthusiasts who add tons of vcore just for another Ghz?

See less See more

2

vicious_fishes

· #14 · Nov 28, 2009

if it wouldn't be making any difference then i fail to see why anyone's fussed.

BLADEY

· #15 · Nov 28, 2009

Maybe saving it until fermi gets realesed, if so i guess we got a few years wait to know what benefits it has

Shadow_UGZ

· #16 · Nov 28, 2009

It seems that it was more of a data synchronization problem between the interconnections rather than heat.

Quote:

However, perhaps due to the complications that most likely arose when trying to synchronize the data transfer between different interconnections, the Sideport was not implemented into ATI's (AMD's) latest graphics chips, namely the HD 5800 series.

Quote:

Instead of tediously searching for good methods to directly synchronize the multi-GPUs, the company used the connectivity possibilities of the PCI Express to make up for the lack of direct cooperation between the graphics cores (starting with PCI Express 1.1)

rico2001

Discussion Starter · #17 · Nov 28, 2009

Sideport was not designed to add performance, it was to maintain it. You all have seen the benchmarks for all of the X2 cards up to this point. The 4580 X2 and the 4870 X2, both perform, within 1-2% of the performance of (2) cards in crossfire, thus ATI saw no need to enable sideport (extra 10GB/s of bandwidth) for both 4800 X2 cards, that they thought they might need.

The same applys to the 5970 and 5950. They saw clock for clock, compared to (2) cards in crossfire, the 5970 saw no decrease in performance. So also not needing the sideport, ATI decided to remove it from the card. If there was a major decrease in performance compared to (2) cards in CF, you would have seen sideport on the card and enabled.

Quote:

The sideport is an advanced interconnect technology introduced in the ATI Radeon HD 4870 X2 to deliver additional bandwidth if and when needed. To date, the improved Gen 2 PCI Express bridge in the ATI Radeon HD 4870 X2 has provided more than enough interconnect bandwidth without use of the sideport, however its inclusion does provide headroom for future applications. -AMD

See less See more

OmegaNemesis28

· #18 · Nov 28, 2009

Quote:

Originally Posted by vicious_fishes

View Post

if it wouldn't be making any difference then i fail to see why anyone's fussed.

Me too.
Ok, so the tech is busto. Can we perhaps move on? It's not like anything is gained and/or lost by not having the sideports.

See less See more

K3VL4R

· #19 · Nov 28, 2009

Quote:

Originally Posted by vicious_fishes

View Post

if it wouldn't be making any difference then i fail to see why anyone's fussed.

Exactly.

So they put the Sideport in the 48X0 X2's just in case it was needed. It was not needed so they decided to exclude it into the 5890. It is saving the consumer money by excluding it from the cards. Or were there people here that wanted it included so that they could keep asking when are they going to enable the Sideport with every driver release, hoping for some bonus performance from their cards ?

See less See more

voice

· #20 · Nov 28, 2009

When they created Sideport their Crossfire drivers weren't as good as they are now.. Oh bugger it i cba to explain; i'll quote an engineer from ATI instead... (In case you're wondering why I emphasized this, it's because none of you are engineers in the slightest and none of you work or have worked for ATI)

Quote:

Originally Posted by Interview with Dave Baumann

A reader question: I had a user question asking, what happened to Sideport (XSP)? Sideport was intended to add more interconnect bandwidth. It has been disabled ever since the release of the RV770 (X2) from day 1. We heard that "that much bandwidth is not needed". IMO... you can never have enough bandwidth really. What was going on there?

Answer:
This is simply a case of our software capabilities catching up to our hardware capabilities.
When the initial design of the RV770 was taking place and concepts such as Sideport were being kicked around our ATI CrossFireX™ software wasn't in the place it is right now, so there was a much higher reliance on inter-chip communication.

While having lots of bandwidth is rarely a bad thing, the ATI CrossFireX communication bandwidth between two discrete cards is less than local bandwidth - even though Sideport doubles the inter-GPU communication bandwidth on an X2 type solution it's still not significant enough to really change the disparity in local frame buffer and inter-GPU bandwidths.

The software work that occurred in the space of time between the RV770 design and product saw significant improvements in inter-GPU communication. Internal to the driver we now have a number of "alternate frame rendering" (AFR) profiles, with many parameters that can be tweaked in order to control how the rendering behaves over multiple GPU's and reduce the inter-GPU communication as much as possible. By the time we put two RV770's on a board and started testing Sideport, the current ATI CrossFireX software capabilities delivered more than enough bandwidth, obviating the need for Sideport.

See less See more

1 - 20 of 35 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.