Introduction

ATI may be having some issues at the very top of the graphics scale, at least until the company answers the NVIDIA GeForce 8800-based challenge, but their performance in the lucrative mainstream market is even more troubling. Here, NVIDIA offers up the very popular GeForce 7600 GS and GT 256MB cards, catering to the entry-level and high-end of this $100-$199 buying range. ATI initially countered with the Radeon X1600 Pro and XT cards, and while competent, these did not have the innate speed to match the GeForce 7600 GT. ATI has since gone back to the drawing board, and emerged with a new mainstream core that effectively doubles the base architecture of the Radeon X1600 XT, and makes it a far more dangerous competitor. The result is the improved Radeon X1650 XT, which powers the ASUS EAX1650XT 256MB card, and is a GPU that just might give the GeForce 7600-based line some problems.

The Radeon X1650 XT

First off, it's important to clear up any misconceptions about the ATI Radeon X1650 line of cards, which includes both the Pro and XT models. These are two very different animals, and while the Radeon X1650 Pro is simply a renamed Radeon X1600 XT on an 80nm (down from 90nm) core, with a slight jump in clock speeds, the Radeon X1650 XT represents a quantum shift for ATI's mainstream line. Why ATI chose to go this route is anyone's guess, but while the Radeon X1650 Pro is really an 80nm Radeon X1600 XT, the Radeon X1650 XT uses the new RV560 core, which probably has more in common with an X1800 GTO.

The initial Radeon X1600 Pro/XT and X1650 Pro cards featured the RV530/535 core, which includes 4 pixel pipelines (a quad), 4 texture units, 5 vertex shaders, and 4 ROPs. This is pretty low-scale even for a mainstream card, but the addition of 3 pixel shaders per pipeline, for a total of 12, helped make up the difference, especially in SM3.0 games. The Radeon X1650 XT uses a more powerful 80nm RV560 core, which effectively doubles the base specification of the RV35X, and sports 8 pixel pipes, 8 texture units, 8 vertex pipelines, and 8 ROPs. There are also 3 pixel shaders per pipeline, which translates into a total of 24 under this architecture. Unfortunately, the basic memory architecture remains the same, with a 128-bit link to 256MB of GDDR3 through a 256-bit internal ring bus.

The clock speeds of the Radeon X1650 XT have stayed very close to the Radeon X1600 XT, and when combined with the doubling of the internal GP architecture, results in some very impressive performance specifications. The default Radeon X1650 XT core speed is 575 MHz and the memory is clocked at 1.35 GHz, which provides theoretical fill rates of 4.6 GPixels/s, 4.6 GTexels/s (standard) and 13.8 GTexels/s (shaded). This last figure gives us an idea of how powerful the Radeon X1650 XT can be in pixel shading exercises, which are prevalent in high-end SM3.0 games. The memory clock speed is a more sedate 1.35 GHz, which translates into a memory bandwidth of 22.1 GB/s, or about on par with the Radeon X1650 Pro and GeForce 7600 GT. The Radeon X1650 XT also includes support for AVIVO, up to 6X AA & 16X AF modes, 3Dc+ texture compression, and ATI's CrossFire multi-GPU technology.

The ASUS EAX1650XT 256MB Card

The design of the EAX1650XT 256MB is quite different from the ATI reference format, and ASUS has definitely gone with its own take on the Radeon X1650 XT. The card's PCB is the same physical size, but while the heatsink-fan is smaller in terms of coverage, it has a bigger fan and its copper fins are also larger. This fan is also a slightly louder than a standard ATI unit, but the ASUS EAX1650XT 256MB is extremely stable, so we're not going to second-guess the decision. The ASUS card is still a single-slot design, but the higher profile of the heatsink-fan means a tighter fit for adjacent PCIe or PCI cards. The other main difference is the presence of an external power connector, something that is not required on the ATI reference design, but is needed for the ASUS EAX1650XT.

The ASUS EAX1650XT 256MB is a single-slot PCI Express card that features a range of connectivity options. The card's backplate includes dual DVI ports, an S-Video/HDTV-out port, and it offers display resolutions up to 2048x1536 (DVI). HD output is handled through a bundled breakout cable, and dual VGA is available using the included VGA-to-DVI adapters. The card's clock speeds have remained on par with the reference specifications, and have been set at 574 MHz core and 1.35 GHz memory.

The retail EAX1650XT 256MB package has a selection of hardware and software, including the card itself, a PCIe power cable, two VGA-DVI adapters, one HDTV composite breakout cable, a SpeedSetUP Guide, a user manual CD, a driver/utility CD, a CD wallet, dual CrossFire Bridges, and a full copy of GTI Racing. ASUS also offers a selection of gaming utilities like GameLiveShow, GameFace Messenger, and GameReplay. There is a CrossFire edition of the EAX1650XT 256MB that sells for slightly more than the standard model, and allows for dual card setups.

To give a better idea of the architecture of the various mainstream and high-end cards we see competing directly against the ASUS EAX1650XT 256MB, here is a small chart outlining the key architectural features of each GPU:

The next chart provides the base clock speed, bandwidth and performance specifications that go along with the above chart, and helps paint a better picture of the individual cards and their capabilities.