ATI's Multi-GPU Solution: CrossFire
by Anand Lal Shimpi & Derek Wilson on May 30, 2005 9:00 PM EST- Posted in
- GPUs
The Problematic South Bridge
While it's hardly talked about outside of Taiwan, ATI's South Bridge is quite buggy. The chip that is responsible for providing the motherboard's SATA and USB ports, as well as PCI slots is no where near final and many manufacturers are skeptical of ATI's ability to finish their own South Bridge in time. Note that ATI's own South Bridge does not support SATA-II or NCQ, regardless of actual bugs with the chip.
Luckily, ATI has partnered with ULi to offer working South Bridges that are compatible with ATI's CrossFire North Bridge. We've tested ULi's South Bridges and they seem to be problem-free, and our sentiments are echoed by many motherboard manufacturers who have decided to use ULi South Bridges with their ATI CrossFire motherboards.
However, ATI is pushing most of their partners to use ATI's own South Bridge despite its problems and is convinced that the problems will be sorted out in time. So a number of manufacturers at Computex are showing off CrossFire solutions with ATI's South Bridge, despite their complaints to us about the South Bridge.
At least this time around, it may be better for motherboard manufacturers to use ULi's South Bridge until ATI has had more time to get all of the kinks out of their solution. ULi's South Bridges have been in use for the past generation of ATI's chipsets, thanks to issues with ATI's South Bridges, and so far, we have not heard of any complaints.
ATI should be focused on the overall platform, not necessarily building up support for their South Bridge. Although, we do think that it is a bit embarrassing to have to turn to another chipset vendor to provide working South Bridges for your motherboard partners. It would be one thing if this were ATI's first chipset, but it most definitely is not.
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yacoub - Tuesday, May 31, 2005 - link
Is it just me or do several things about this scream "bottleneck" and "latency"? The 2PCI-E x8 slots instead of x16 slots. The extra Compositing Engine chip. The ability to pair different cards such that it will drop clock speeds and/or pipelines to sync them up. The lack of direct chip-to-chip interconnect.I'm curious to know just how much performance gain is realized if you pair, say, an X800XL and an X850-something, over just the X850-something. And also how much bottleneck and latency there is in this implementation over the NVidia offering of SLI.
The only upside I can see is cost/upgrade since a user can own an X800-based card (assuming they have a Crossfire compatible motherboard) and go out and buy an X850-based card later and use BOTH cards together (assuming they are both Crossfire-capable cards). Then again with those assumptions I'm not sure it's truly any more cost-effective. =\
LoneWolf15 - Tuesday, May 31, 2005 - link
As usual, the fanboys of both sides come to the show to spout their comments.For everyone saying "Man, you have to buy a Crossfire that matches your card, and throw it away when you upgrade"...umm, don't you have to buy two of the exact same matching card for running nVidia SLI, and if you wish to upgrade, you have to sell both? Doesn't sound that different to me. One thing I think a lot of current ATI owners will be happy about is that they won't have to get rid of a card they already own and buy two of a new one; they can just buy a single Crossfire card (and of course a mainboard).
On the other hand, to those thinking ATI has now "0wned" nVidia, it is WAY too early to tell. The solution looks promising, but if you have to sacrifice mainboard performance (i.e., SATA hard disks, memory bandwidth, etc.) it may be a hard sell. Benchmarks in Doom 3 are also not the end-all be-all. We'll have to wait for a more comprehensive performance review, including DirectX benches, and performance/quality with older games using this new AA method, as well as game compatibility reports. We'll also need to know what TRUE pricing is (we've seen claimed pricing vary quite a bit from what it has turned out to be at product release in the past two years).
Do I hope it will beat nVidia's solution? You bet. I like ATI, but even more I like competition that drives the industry. Do we proclaim ATI the winner/loser on this one? Heck no, it isn't even a purchaseable product yet.
ElMoIsEviL - Tuesday, May 31, 2005 - link
23 - They ran Doom3.It's not an ATi game at all as we all know. And it still does REALLY well. And it's not in release stages yet.
;)
ElMoIsEviL - Tuesday, May 31, 2005 - link
hehehehe.. it's better then SLi... heheheheFigures, all the NV on here prolly aren't too happy today.
I can't wait to test out the new AA modes.. :)
vertigo1 - Tuesday, May 31, 2005 - link
This is insane, who on earth will buy this?!JarredWalton - Tuesday, May 31, 2005 - link
30 - Yes. The PCIe bus likely provides slower performance, as it is used for lots of other things (like communication between the CPU, RAM, and GPUs). I believe NVIDIA SLI works without the dongle but at slower speeds - at least, I heard that somewhere, but I haven't ever had an SLI board so I can't say for sure. Anyway, since DVI is a digital signle, using DVI in/out seems about as good as the SLI bridge - at least in theory. Now we just need to wait and see how theories pan out. :)Jalf - Tuesday, May 31, 2005 - link
I was under the impression they were going to use the PCI-E bus for transferring data between the cards. Is the external dongle going to handle that instead?Murst - Tuesday, May 31, 2005 - link
I really don't see how the xfire is better than sli based on hardware compatibility. Sure, you don't need the exact same cards, but you will likely buy only one x850 type card per x850 xfire. It would be extremely unlikely that someone upgrades from x850 xt pro -> x850 xt pe.Basically, in the end, you will buy a specific xfire tailored to your gfx card, and throw it away with the next generation of cards.
gxsaurav - Tuesday, May 31, 2005 - link
Great this just means more heat, man, even a single 6800 nU playes everygame fine, while running coolViRGE - Tuesday, May 31, 2005 - link
#21, yes it is. This is what hurts ATI the most, Nvidia already had 4 release cycles of experience with motherboards(2 of those being highly popular, highly recommended boards) before attempting SLI. ATI has a previous launch for a board almost universally ignored. I would not use an ATI board at this time, so I would also not consider CrossFire. ATI needs to get CrossFire working on Nvidia's boards to have a fighting chance this round.