3D rendering technology for two video accelerators providing corresponding performance gain, ATI CrossFire, was introduced in May. Yesterday there appeared official test results of such systems. But without any notice, there were also announced chipsets supporting the new technology on the motherboard level. They got a logical (though a very long) name - ATI Radeon Xpress 200 CrossFire Edition.
ATI Radeon Xpress 200 CFE
So, the name implies that we cannot expect anything new from these chipsets. Indeed, the only thing they actually add to Xpress 200 is the support for two graphics slots. As the originals didn't undergo deep changes, two PCIEx16 slots operate in the same way as in their competitor: x8+x8. In future we'll probably see chipsets with sterling x16+x16 for this mode. As for now, ATI engineers also limited themselves to a small update, as in the products of the direct competitor — NVIDIA nForce4 SLI differs from nForce4 Ultra only in its capability to switch between one (x16)/two(x8+x8) video cards.
This time we have an opportunity to examine Xpress 200 CFE for AMD
platform (RD480), based on the Xpress
200P chipset (RX480). But the company is going to launch a similar
couple (RD400) for the Xpress
200 IE chipset (RS400). What concerns additional differences of
our today's product under review from its predecessor, we should note
that our engineering sample is equipped with the IXP450 (SB450) south
bridge. It didn't require overhauling the north bridge, as the IXP450
and the IXP400 have compatible bus interfaces (their layouts are also
compatible, so the present south bridges from ATI are interchangeable
even on the level of a given motherboard). Differences between the
SB400 and the SB450 are minimal. The only difference, noticeable by
eye, is the High Definition Audio support in the latter instead of
outdated AC’97. Moreover, we should wait for production-line
motherboards before speaking of ATI Xpress 200 CFE functionality -
the significantly improved SB500 south bridge is expected soon (SATA
II support, etc). This component of ATI chipsets used to be often
replaced with the compatible ULi bridge (M1573). There will be probably
no modification with integrated video and CrossFire support (at least
for the AMD platform).
So, CrossFire obviously requires two graphics slots (PCIEx16). But does it mean a certain CrossFire Edition chipset? Formally no. Theoretically, NVIDIA nForce4 SLI chipsets as well as modern Intel chipsets (which allow two PCIEx16 slots on a motherboard with due efforts of enthusiasts) and some products from Taiwanese chipset manufacturers must allow CrossFire. Unfortunately, in practice we had no time to analyze this issue thoroughly. But according to early info, two ATI video cards failed to work in tandem on nForce4 SLI. ATI specialists assert that [video] drivers do not contain checks for [admissible] chipsets. That's quite logical for marketing as well as purely technical reasons. Nevertheless, we'll have to wait for the production-line samples in order to find out the applicability limits of CrossFire. Here is the current state of affairs: according to ATI, the Xpress 200P CFE chipset is an ordinary product with unassuming functionality and obscure availability (the first samples had been presented as far back as in spring); but according to practical results, it's a unique chipset. Motherboards on this chipset must generate queues of numerous (?) CrossFire fans. The time will act as an arbiter, as usual.
In conclusion, a few words about our engineering sample of a motherboard on ATI Xpress 200P CFE. Unlike similar motherboard samples on RX480/RS480, this model looks imposing, even though it's manufactured by ATI. It has an expert layout and a lot of modern integrated periphery — it's ready for retail at once. But what impresses you the most at first sight is three large heatsinks: we have an impression that RD480 is a three-bridge chipset :). But in fact, the third heatsink (the largest, by the way) covers an impressive group of field-effect transistors in the circuit of the CPU voltage regulator with a thermal diode at the surface of the heatsink. A huge number of settings in BIOS Setup allow system optimizations. In particular, we had no problems with setting all the main memory timings to minimum and enabling 1T DRAM Command Rate.
You may read about CrossFire system performance proper in the corresponding article. Our objective for today is smaller — to determine the contribution of the chipset/motherboard to the overall performance level. The answer to this question is evident for all our constant readers: as the memory controller is removed from AMD64 chipsets (it's built into a CPU now), ATI Xpress 200P CFE will be no different from other competitors in terms of memory operations performance. Thus, you shouldn't be bothered by a relatively short list of contenders. Especially as we compare the new product with its direct competitor — NVIDIA nForce4 chipset (in this case — Ultra, but Ultra is no different from SLI in a configuration with a single video card).
A little difference between the chipsets for AMD64 is possible only in terms of operation speed with the graphics interface. Periphery performance is an individual question, of course. This question is all the more vital, as the IXP400 seemed to have performance drops in USB operations. Unfortunately, the deadline and the lack of high-performance USB devices at hand (the difference is negligible in case of regular card readers/memory cards or USB drives) prevented us from finding out whether the IXP450 made progress in this direction. Anyway, we should wait for production samples in view of the above-mentioned pendency with the south bridges in retail products.
Low level analysis of memory performance in our RightMark Memory Analyzer demonstrates that these chipsets are identical almost in all parameters. Only the maximum real memory write rate in ATI Xpress 200P CFE is a tad higher (that's probably the effect of different timings and other low level parameters in BIOS Setup).
Small doubts are allayed by the archiving performance test, the most sensitive test to memory performance in real applications, when set to maximum compression ratio. The results are absolutely identical.
Furthermore, we shouldn't expect any difference in another popular test — encoding video from MPEG2 (DVD) into MPEG4: as a rule, there may be only slight performance fluctuations depending on the real CPU clock. Today's test is not an exception.
As some time ago our 3D application tests revealed interesting deviations in NVIDIA chipsets, it would be very interesting to compare nForce4 with the competing chipset, tested with optimal memory configuration. The SPECviewperf results are surprising: even though ATI Xpress 200P CFE slightly outperforms motherboards on ATI Xpress 200P and VIA K8T890 (they were represented in our lab only by engineering samples, which didn't allow setting the important parameter "DRAM Command Rate" to 1T), the new product is defeated by the NVIDIA chipset, like all the others. A substantial group of tests from this package runs on Xpress 200P CFE and nForce4 Ultra with similar speed. But the difference in two tests exceeds 30%! Thus, we can be sure that NVIDIA chipsets provide low level settings for graphics interface operations, which leads to the above mentioned difference in particular. However, nForce4 does not demonstrate noticeable advantage over its competitors in games, sometimes even lags behind, though it looks impressive in some SPECviewperf tests.
Indeed, ATI Xpress 200P CFE outperforms its competitor in Doom 3 by approximately 5% at low resolution and graphics quality. The difference disappears, as the graphics level increases.
Advantage of the ATI chipset in Unreal Tournament 2004 is steady but minimal — about 2-3%.
nForce4 shoots forward a little in FarCry at maximum resolution, as it did before. But in easier modes its defeat is impressive — up to 15% depending on a demo scene.
Our conclusions on the Radeon Xpress 200 CrossFire Edition are not final yet. It's an average product with moderate functionality on the AMD chipsets market. While the Xpress 200 series chipsets surpassed its competitors at least with PCI Express at the time of the announcement (ATI managed to announce this product earlier than other manufacturers), this formally new product has no advantages. It cannot oppose anything to nForce4 (remember that integrated Xpress 200 is not expected to have CrossFire Edition). However, it holds true only if two video cards from ATI can form CrossFire with a motherboard on any chipset with two PCIEx16 slots. If we raise a query about compatibility of CrossFire solutions with non-ATI chipsets (that seems to be the case for now), the unique nature of Xpress 200 CFE becomes evident.
Add the ambiguity with the functionality [and model] of the south bridge, which will be used in production-line motherboards on RD480, and you will get uncertain prospects of the chipset and even of the CrossFire technology on the whole. What we cannot deny to Xpress 200 CFE is its performance. Of course, it's nothing special compared to other products in 2D mode. But some strange nForce4 optimizations put the ATI chipset to advantage in 3D applications. Unfortunately, our article on ATI chipsets again ends in anticipation for production-line motherboards (and video cards). Shall we see them, that is the question, the Xpress 200 experience is not encouraging.
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