Original Link: http://www.anandtech.com/show/1863

ATI RD580: Dual x16 Crossfire Preview

It took a very long time for ATI's Rx480/482 chipset to make it from Engineering Samples to motherboards an AMD enthusiast would actually buy. However, enthusiast boards are finally in the marketplace from DFI, and we have ATI Crossfire review samples from Asus, MSI, and Gigabyte that indicate boards from Tier 1 makers are finally on the way.

We think you will be particularly interested in a review that will appear in the next few days of the Asus A8R-MVP. It's a mainstream board with mainstream pricing, but the features and OC capabilities will probably surprise many - and it is also the first production board which uses the ULi M1575 South Bridge with SATA2 and fixed USB. Abit also tells us they will have review samples of their ATI Rx482/ULi M1575 available within the next 2 weeks. Abit blames their launch delays on constrained shipments of the same ULi M1575 south bridge.

All of this is good news for those looking for an alternative chipset in the AMD Athlon64 market. You will finally be able to choose Socket 939 motherboards from major manufacturers, targeted at the AMD enthusiast, and based on the ATI Rx480/482 chipset.

The ATI Story on the X1800XT Delays

We took the opportunity while talking with ATI to ask about the crippling delays of the ATI X1800XT and the X1xxx family. There are so many rumors in the market place; we wanted to hear ATI's explanation of why it took so long for X1800XT to make it to market. Was the problem the 90nm die-shrink as many had speculated?

ATI told us emphatically the delays with X1800XT were NOT the result of the die-shrink to 90nm. We were told the issue was a defect in a third-party IP (Intellectual Property) that was used in the x1800XT GPU die. It took ATI quite a while to find and correct this design flaw. Why does this matter? Since this flaw was specifically related to the X1xxx family, design work continued on future video cards, and there were no delays on that front. Development continued on introductions that will follow R520, which means the R580 GPU is still scheduled for launch in January.

Looking Ahead - RD580 & Manta

Even though ATI RD482 chipset Crossfire boards are just appearing in the market, ATI is already far along in the development of their next chipset, called ATI RD580. We recently had an opportunity to spend two days testing the new RD580 Crossfire motherboard, code-named Manta, and to directly compare the RD580 Dual X16 chipset with the recently reviewed Asus A8N32-SLI Deluxe featuring the nVidia Dual x16 chipset. The comparison included both single and dual video card head-to-head testing with 7800GTX SLI (running 81.87 drivers) and X1800XT Crossfire (running Catalyst 5.11).

Because X1800XT Crossfire and The RD580 chipset have not yet officially launched, ATI has asked that we not publish hard benchmarks of our results, since they will likely change in final release versions. We can, however, talk in general terms about performance. Those of you who believe ATI is far behind nVidia are in for a surprise.


ATI's AMD Athlon64 chipsets began with a bang almost a year ago with the "Bullhead" Reference Board. In our review of the first Radeon Xpress 200 Reference board, ATI was clearly aiming for the AMD Enthusiast. This continued with the all-white "Grouper" this past July, and the black "Halibut" which was reviewed as the Crossfire AMD in late September. Despite three generations of capable Enthusiast chipsets based on the Radeon Xpress 200 core, we only began seeing ATI AMD chipsets used in Enthusiast motherboards with the launch of Crossfire. The first ATI enthusiast board was the DFI LANParty UT RDX300 reviewed less than a month ago. Now we are finally seeing Tier 1 manufacturers like Asus, MSI, and Gigabyte with ATI Crossfire AMD boards starting to ship.

Click to enlarge.

The Manta Reference board is a distinctive clear blue with Red slots and peripheral connectors. ATI seems to have no lack of Fish names or unique board color schemes, so Manta carries on a tradition that could soon stock an aquarium. Some love the fish internal development names, some hate them, but they are definitely unique.

When we recently reviewed the nVidia Dual x16 board we saw a dual chip setup with PCIe channels split between two multipurpose chips.

The nVidia dual x16 design provides one x16 PCIe off the "north bridge" or SPP and one x16 PCIe off the "south bridge" or MCP. On the AMD side the North chip is the MCP51 which communicates with the CK8 south chip over 16-bit HTT connections. The Intel dual x16 uses the same CK08 SLI south bridge as the AMD chipset, but the North chip is C19. C19 forces communications between the North and South chips to 8-bits.

The ATI RD580 also uses a North Bridge/South Bridge configuration, but all PCIe channels reside in the North Bridge and both PCIe x16 slots are driven by the North Bridge Chip. The new RD580 north supports 44 lanes and can be combined with any of the south bridges than can be used with the Rx480 chipset. This includes the ATI SB450, the revised pin-out SB460, the upcoming SB600 with SATA2 and revised USB, and the ULi 1573/1575.


While ATI has used the current SB450 South Bridge in the Manta we evaluated, we expect the shipping Manta Reference Board will use the new SB460. SB460 is identical in function to SB450, with the same fast feature performance, but limited USB and no SATA2 or NCQ. It is important because it is pin-compatible with the upcoming SB600. This means boards designed with SB460 will be able to drop in SB600, with revised USB, SATA2, and NCQ as soon as this new South Bridge is available - possibly as early as January. Manufacturers can also combine the RD580 Dual x16 North Bridge with the ULi M1573, or more likely the ULi M1575, which supports SATA2, NCQ and competitive USB.

HD Audio

ULi was actually the first to annonce HD Audio on the AMD chipset in April of 2004. However, ATI was the first major manufacturer to bring High Quality HD audio to their AMD product line with the introduction of the SB450 South Bridge for the Xpress 200 chipset in the late 2004. HD support continued with the Crossfire AMD chipset. This advantage continues with RD580, which features the Realtek ALC882D HD audio codec on the Reference board.

Overclocking and Integrated Graphics

For the past year we have watched ATI evolve as a chipset maker for the AMD Enthusiast. Each subsequent chipset seems to get better and offer more options and features AMD hobbyists have asked for. So what's new for the Enthusiast on the RD580?

First and foremost, the RD580 breaks the HTT barrier in overclocking. Overclockers are used to having to drop HTT to 3X or 600HTT for their highest overclocks because the limit on current AMD HTT is 1000. RD580 requires no drop in HTT for even the highest overclocks. We were able to achieve overclocks in excess of 300 with HTT set at 5X. Utilities which showed HTT frequency indicated we were actually running at greater than 1600 HTT at these settings.

It is clear ATI has found a way around the current AMD limitation of 1000HTT, which will be a breath of fresh air to those trying to squeeze the most performance from their Athlon 64 processor. So how well does RD580 overclock? We can't quote exact numbers, but we can tell you the RD580 BIOS has not yet been tweaked for memory compatibility or top memory performance. We also used our own known OCZ PC3200 Platinum Rev. 2 dimms in testing since we are very familiar with how they perform. Even with the untweaked BIOS, we still reached overclocks even higher than the excellent performance of the Crossfire AMD Reference board! We can only speculate where this board might end up, but it is already a very exciting overclocker.

Integrated Graphics

Some may have noticed there is no small x in RD580, and they would rightly guess it means there is no Integrated Graphics version of the 580 chipset. RD580 will only exist as a Dual X16 chipset for discrete graphics.

ATI will soon launch the RS485 for Integrated Graphics. RS485 is a die-shrink of the RS480 chipset to .11-micron. This has allowed ATI to raise the graphics clock from the 300 used for RS480 to 400MHz on RS485. RS485 is expected to compete very well with the nVidia high-end GeForce 6150 chipset.

Performance: X1800XT Crossfire vs. nVidia 7800GTX SLI

We were pretty excited as we ran a head-to-head of ATI X1800XT Crossfire (5.11 Drivers) on the ATI RD580 Dual x16 to nVidia 7800GTX SLI (81.87 drivers) on the Asus A8N32-SLI Deluxe Dual x16. This is, after all, the comparison everyone would like to make if all the parts were available. Unfortunately ATI asked us not to publish specific benchmarks since RD580 and Crossfire x1800XT have not been officially released and there may be more changes before the products launch. However, we will talk about relative performance after detailing the setup and some new findings.

ATI was roundly criticized for the inability of X850XT Crossfire to run at resolutions above 1600x1200, even though most end-users are not actually able to run at higher resolutions with today's most common 19" and 20" flat-panel displays. We confirmed that the new compositor chips used in X1800XT Crossfire do indeed run fine in Crossfire mode at 2048x1536. ATI tells us there is no limitation in the X1800XT compositor that would prevent even higher resolutions from working as they should.

While the exact performance results achieved comparing X1800XT Crossfire with 7800GTX SLI can not yet be published, we can tell you we benchmarked with F.E.A.R., Quake 4, Splinter Cell - Chaos Theory, Doom 3, Far Cry, and 3DMark05 at 1600x1200 resolution with 4X AA and 8X AF enabled. ATI X1800XT Crossfire won every benchmark over nVidia 7800GTX SLI in these tests.

We also ran standard scores (1024x768) for Aquamark 3, 3Dmark03, and 3Dmark05. Once again Crossfire X1800XT outperformed nVidia 7800GTX SLI in every benchmark.

We then ran all the same tests in single video mode, comparing a single X1800XT on the ATI RD580 to a single 7800GTX on the Asus A8N32-SLI. Benchmarks were run under the same conditions as Crossfire/SLI - 1600x1200/4xAA/8xAF in games and "standard" scores in 3Dmarks and Aquamark 3. Once again the ATI X1800XT on the RD580 was the winner in every benchmark. It is clear the new 5.11 drivers do make a difference in Open GL games like Quake 4 and Doom 3. Even more exciting, the RD580/X1800XT Crossfire will be a potent graphics combination.

There is no doubt that the nVidia 7800GTX 512MB, which everyone expected would launch 2 days ago as a 7800GTX Ultra, would likely win a head-to-head performance test as single or SLI when compared with the single X1800XT or Crossfire. However, ATI clearly believes the competitor for X1800XT is the $499 7800GTX and not the $700 7800GTX 512MB. ATI was quite clear they will be introducing a "PE version" of X1800XT to compete with 7800GTX 512.

Our Take

ATI's chipset Engineering team seem determined to take ATI chipsets to new levels to grab the attention of AMD hobbyists. They seem right on target, since the AMD market has been, and continues to be, driven by the computer enthusiast. Our preview of RD580 on the ATI Manta Reference board showed us some exciting developments are on the way from ATI. Dual x16 video capabilities in a single chip 44 PCIe lane package certainly performed extremely well compared to the just released Dual x16 from nVidia.

The possibility of HTT ratio-free overclocking will also interest the real overclockers out there. Running over 300FSB with a 5X HTT multiplier with current Athlon64 chips seemed an impossibility until we saw it working for ourselves in RD580. We are also glad to see ATI continue their commitment to quality audio on the AMD platform with continued support for High Definition audio codecs. Audio is one area where ATI is clearly outperforming nVidia.

In the comparison of the RD580 Dual x16 motherboard with X1800XT Crossfire to Asus A8N32-SLI with 7800GTX Crossfire, X1800XT Crossfire won every benchmark. That means if RD580 and X1800XT Crossfire were shipping today the graphics war would be on and plenty hot. The reality, however, is that X1800XT Crossfire and X1800XT PE are "coming soon", while nVidia's offerings are available today. ATI RD580 will likely land in early to mid January. We also expect the nest generation ATI R580 GPU to land about the same time. ATI is also hard at work on Socket M2 offerings to be launched with that AMD socket.

Based on what we have seen in this RD580 preview, the worries at ATI right now are more about the present than the future. Future solutions look very competitive and exciting to the market. ATI seems to be caught in a release "Twilight Zone", but as they work their way through current release nightmares, the future looks as if it could be very bright again for ATI. Certainly the upcoming RD580 Dual x16 chipset, X1800XT Crossfire, and X1800XT PE look more than competitive. Add to that R580 is just around the corner and it looks as if ATI has the goods coming to erase the last nine months of disappointment

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