The 890GX Chipset

As we just mentioned on the previous page, the 890GX chipset doesn’t offer next-gen graphics. In fact, the Radeon 4290 IGP is simply a higher-clocked derivative of AMD’s 785G chipset. Core clock is 700MHz.

If you recall the relationship between 780G and 790GX, you’ll remember that AMD followed the same strategy with these platforms as well. The 790GX was based on the same graphics core found in the 780G, only AMD bumped the clock up to 700MHz.

All four IGPs are largely based on ATI’s RV620 GPU. This is the same GPU found in the Radeon 3450/3470 launched in January 2008 – two years ago. And don’t forget that RV620 was merely a die shrink of the RV610 chip used in the Radeon 2400 from 2007. Clearly this isn’t cutting-edge technology.

To AMD’s credit though, the Radeon 4200 IGP found in the 785G was updated to include DirectX 10.1, HDMI 1.3, and UVD 2 support. UVD 2 includes support for hardware-accelerated picture-in-picture for watching Blu-ray movies, and video enhancement features like dynamic contrast, HD color enhancement (including flesh tones and color vibrance), and post-processing effects like noise reduction, de-interlacing and HD pulldown detection. The 42xx series IGPs also supports video transcoding on the GPU, freeing the CPU up from performing this task.

Unfortunately, HTPC users will be disappointed to hear that the chipset lacks support for bitstreaming HD audio, and LPCM audio over HDMI is limited to just two channels.

AMD’s IGPs all feature 40 stream processors, with the 780G and 785G relying on a 500MHz core clock, while the graphics core on the 790GX and 890GX run at 700MHz. Besides higher clock speeds, one neat feature AMD adds to the GX series chipsets is Sideport memory. This is a pool of memory that’s dedicated just for the IGP, enhancing performance. In order to reduce costs, the G chipsets lack Sideport memory.

Because the 790GX and 890GX chipsets are outfitted with the same number of shaders and identical clocks, the only differentiator as far as 3D gaming performance is concerned is the 890GX’s addition of DirectX 10.1. Only in games that utilize DX10.1 to provide enhanced performance for lighting effects like screen space ambient occlusion (SSAO) will the 890GX be able to pull away from the 790GX.

As anyone that’s run STALKER: Clear Sky or Call of Pripyat can tell you though, SSAO is a very graphically-intensive effect, it’s possible that the Radeon 4290 IGP doesn’t have the shading horsepower to run this and still deliver playable performance. We’ll be testing this theory out with Tom Clancy’s HAWX later in this review.

Like other AMD chipsets, the 890GX retains support for ATI SurroundView, and the IGP itself can drive up to two displays. Hybrid Graphics support is also provided, with support limited to the Radeon 5450 GPU. With this feature you can pair the Radeon 4290 IGP with a Radeon 5450 graphics card to improve 3D performance (similar to CrossFire). Hybrid Graphics support is limited to just five titles (Battleforge, Bioshock, Company of Heroes, HAWX, World in Conflict) with the Catalyst 10.3 beta we used for testing though, and AA/AF isn’t supported yet either, so we skipped testing this feature.

For enthusiasts who may want to run two graphics cards at some point down the road, 890GX also offers CrossFire support. When two cards are installed for CrossFire, the PCIe lanes will be split evenly between the cards, with 8 lanes for each graphics slot (vs all 16 lanes when one card is used).

While the IGP is pretty familiar, AMD has made a couple of improvements with 890GX however. AMD has doubled the bandwith linking the North Bridge to the South Bridge. The most significant addition to 890GX is without a doubt, its SB850 South Bridge.

SB850 is a brand new chip that’s been designed to address SB750’s shortcomings. It offers more USB support (14 USB 2.0 ports in SB850 versus SB750’s 12), a native Gigabit Ethernet MAC, and two additional x1 PCIe 2.0 lanes.

Its most notable feature though is its 6Gbps SATA support, a first for any chipset. SB850 supports up to six 6Gbps SATA drives.

One additional feature you’ll see many motherboard manufacturers pushing with their 890GX motherboards is USB 3.0 support, but this isn’t natively provided by the chipset, instead it’s provided by an external USB 3.0 controller. NEC’s USB 3.0 controller is the popular one at the moment, as it was the first to receive certification, but the downside is that NEC’s controller is limited to supporting just 2 USB 3.0 ports. A native solution would’ve provided USB 3.0 to all of the motherboard’s ports. Oh well.

Thankfully, to facilitate full-speed USB 3.0 transfers, AMD’s chipset team did think ahead and provides an x1 PCIe 2.0 link that hangs off the 890GX North Bridge. More specifically, six x1 PCIe 2.0 lanes are provided. AMD tells us that besides USB 3.0, motherboard manufacturers could use this to provide added features like additional SATA controllers, LAN, x4 PCIe slots, etc.





Going back to USB 3.0 though, the significance of integrating PCIe 2.0 lanes on 890GX instead of PCIe 1.0 should give them an advantage over competing H55 chipsets from Intel, which still rely on PCIe 1.0. This could lead to bottlenecks on H55 boards with USB 3.0 and 6Gbps SATA, as you’re limited to just 250MB/sec bandwidth. USB 3.0 alone tops out at 480MB/sec.