ATI 'Crossfire' practical issues

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Nick

Veteran
ASSUMING The Inquirer's rumors are correct:

ATI Multi VPU will be called Crossfire
ATI Crossfire Multi VPU does split screen

...wouldn't this cause technical problems? For example suppose the master card has a different feature set, different performance, different internal quality, or even hardware bugfixes!

SLI disalows even cards from different vendors (is this strict)? And obviously this helps preventing a lot of issues, but it's a restriction for consumers who wish to upgrade and can't easily find the same model.

Your opinions? Let's not take any of the rumors for truth but discuss the technical aspects... Does anyone expect second generation SLI to be less restrictive?
 
Nick said:
For example suppose the master card has a different feature set, different performance, different internal quality, or even hardware bugfixes!
Click to expand...

You think there would be no restrictions on this?

I think the number of times I've said that it is highly unlikely that different generations of boards will operate together because of these types of issues exceed the digits on both hands. I also know I was correct in saying that.

Slightly differing performances and bugfixes are likely to be less of an issue (bug fixes within a generation rarely affect anything that would be noticeable).
 
we`ll this is how i(TM) see things...
there should be no "real" problems in using 2 diffrent cards in AFR and SFR mode.
issues like card preformance, and feature support can be easily solved.
since there is no "official" support for duel gfx proccesing by either the OS or the API, MVP like SLI will work by fooling your system into thinking there is only one card involved leaving the workload distrebution to the driver. in a case when there are two diffrent features sets cards involved, i.e. an SM2.0 and an SM3.0 cards, the driver will expose the SM2.0 card to the OS and the app, "forcing" it to utilize the proper mode, since SM3.0 hardware doesnt have any problems working under SM2.0> modes there are no "major" compatibility issues.
about the preformance issue, well there is no other solution other then simply make the faster card wait, other then lower frame rates there should be no problems at all, atleast i dont see any. :?
the only problamatic mode will be the super tiling mode, in which i dont see how you can overcome the compatibility issues, but my insight in this matter is fairly limited so i could be and prolly overlooking something/s.
i hope some one could clearify more about solving those issues under s.tiling mode. :oops:

btw i still dont get all this nonesence about "master cards", i think its just a bunch of crap and missunderstud rumors.
 
DaveBaumann said:
You think there would be no restrictions on this?
Click to expand...
No. That's exactly why I started this thread. ;)
I think the number of times I've said that it is highly unlikely that different generations of boards will operate together because of these types of issues. I also know I was correct in saying that.
Click to expand...
It surprises me that different sources keep rumoring support for combining an old slave card and a new master card. Either this means the 'new' cards are totally identical to existing cards except for the cross-comunication, or they somehow synchronize features, performance and quality of both cards.

Or would all the rumors be completely false?
 
DOGMA1138, lowering features and performance to the same level as the slave card isn't really going to make Crossfire popular. Obviously if someone buys a card with Shader Model 3.0 (and other) capabilities, he'll want to be able to use them. Also, dual-GPU doesn't give anough of a performance increase to justify keeping the old card and slowing down the new card. In both cases the consumer is better of with only the new generation card, and Crossfire is useless. Only when combining two new cards it's an interesting setup. But that's nothing new.

So if the rumors are false, wouldn't it hurt ATI not to correct them? Else there must be some truth in it, and I'm curious what the possibilities are.
 
Actually, the only real problematic issues will be with OpenGL, where in some cases there is no overlap in support. So even if there is support for combined rendering with ATI + nVidia cards, it is unlikely to be a good solution.

Personally, I don't see much reason to support anything but identical (or nearly so) video cards. Even combining a card with one that is half as fast will offer little to no noticeable improvement (and would be likely to drop performance in cases that are hard on SLI-type scenarios, such as render to texture).
 
If (and I mean if) the upcoming cards should prove to have double the power of the current gen cards, coupling that with one of the current gen cards (dumbing it down to SM2 effectively) would be pretty useless, since you'd end up with the performance you already have with the new gen card in single mode. So I guess that won't really be a viable option.
 
Nick said:
DOGMA1138, lowering features and performance to the same level as the slave card isn't really going to make Crossfire popular. Obviously if someone buys a card with Shader Model 3.0 (and other) capabilities, he'll want to be able to use them. Also, dual-GPU doesn't give anough of a performance increase to justify keeping the old card and slowing down the new card. In both cases the consumer is better of with only the new generation card, and Crossfire is useless. Only when combining two new cards it's an interesting setup. But that's nothing new.

So if the rumors are false, wouldn't it hurt ATI not to correct them? Else there must be some truth in it, and I'm curious what the possibilities are.
Click to expand...
im not saying its a good idea to have a slower less advance card draging your new high end system down.
the fact that such configuration can work in theory doesnt mean it will deliver good results.
any way in the bottom line there is no real reason for MVP or SLI atm, its just a pissing contest over 3dmark scores.
tho under MVP AGP+PCIe mobos(like VIA`s one) if say youll buy a midrange R5xx and with you current x800( ) you`ll get preformace which are closer to R5xx high end cards it can be worth it, yes you are giving up features like SM3.0 but if you just want to make your 3Dmark@penis bigger it should do just fine.
 
I don't have any facts, but to think that it'll work with coupling an AGP card with a PCIe card is outright ridiculous from the technical point of view. Maybe it would be possible, but no IHV would punish themselves with a task like that.
 
DaveBaumann said:
Nick said:
So if the rumors are false, wouldn't it hurt ATI not to correct them?
Click to expand...

No company is going to comment on rumours about unannounced technologies.
Click to expand...

Can you imagine what would happen if Inq could generate legitimate info on unnanounced products merely by cranking up the rumor mill even more? :LOL:
 
_xxx_ said:
I don't have any facts, but to think that it'll work with coupling an AGP card with a PCIe card is outright ridiculous from the technical point of view. Maybe it would be possible, but no IHV would punish themselves with a task like that.
Click to expand...
Um, there's such a thing as a motherboard that supports PCIe and AGP right now?
 
there is somthing that called AGPexpress, Albartron made it to support AGP on intel pcie chipsets, basicly its 2 PCI rails combined to give some limited "on paper" AGP support.
 
Not the hardware itself, but the synchronisation, timings, software, drivers - the whole package. You can slap any kind of interfaces together onto a mobo, it doesn't mean it'll all work together effectively. That's not easy at all and also you'll have to do helluva lot buffering (buffering kills performance as we all know).
 
DOGMA1138 said:
there is somthing that called AGPexpress, Albartron made it to support AGP on intel pcie chipsets, basicly its 2 PCI rails combined to give some limited "on paper" AGP support.
Click to expand...
That would be pretty poor performance, though.
 
Chalnoth said:
DOGMA1138 said:
there is somthing that called AGPexpress, Albartron made it to support AGP on intel pcie chipsets, basicly its 2 PCI rails combined to give some limited "on paper" AGP support.
Click to expand...
That would be pretty poor performance, though.
Click to expand...
BIOSTAR NF4ST-A9 / NVIDIA NFORCE 4 / DUAL CHANNEL DDR400 X4 / SUPPORT NVIDIA 7.1CH HIGH DEFINITION AUDIO WITH SPIDF OUT & NVIDIA GIGABIT LAN WITH EXTERNAL PHY / 4 X SERIAL-ATA2 300 W/NVIDIA RAID & ATA133 / PCI-E X16 , 2 PCI-E X1, 3 PCI, XGP-XTREME GRAPHICS PORT, SUPPORT COMPATIBLE AGP CARDS / ATX / UP TO 10 X USB V2.0
Click to expand...
 
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