A Big Chipset in a Small Package

Early this month, AMD released the first of their 800-Series motherboard chipsets – 890GX. The intention is to replace their previous high-end 790GX chipset, which is showing its age. Since then, quite a few middle-range and high-end models have arrived from all the major motherboard manufacturers. Today we take a look at one of the few Micro-ATX versions available today – the 890GXM-G65 from MSI.

The 890GXM-G65 is small, but makes for a good gaming SFF system thanks to its Crossfire support with a pair of full-length PCI-E ports (which run in x8 mode when Crossfire is enabled). The first thing I thought of when I heard we were receiving this board was how sweet it would be in the Silverstone Sugo SG04 case we reviewed a while back, with a pair of Radeon 5970′s running… Yum!

One of the main reasons we’re looking at this board though, is for the introduction of the 890GX chipset. So we’ll take a quick look at what that entails.

The 890GX Chipset

First of all, let’s get this out of the way: The Northbridge component of this new chipset is virtually identical to the 785G (the “mainstream” chipset AMD released last year). The only difference is that the GPU runs at 700 MHz instead of 500. The silicon is identical; they are separated during manufacturing using the familiar binning technique. So the 890GX enjoys the same 40 stream processors and hardware video decoding that made the 785G so great. One tweak that was made is the ability to split the x16 PCI-E graphics lane to a pair of x8 lanes for better Crossfire support. 785G boards with dual graphics support usually only had 4 lanes going to the second port.

So we have to focus mainly on the SB850 Southbridge, which replaces the SB7x0 found on the 700-series chipsets. Let’s take a look at AMD’s nifty diagram:

As you can see (you can click for higher res), the SB850 adds native SATA 3.0 (they hate it when you call it that) 6Gbps support, and 14 USB 2.0 ports (SB710 had 12), and an optional Gigabit Ethernet controller (though every board I’ve seen so far uses an auxiliary controller). They have also added a pair of PCI-E lanes to the Southbridge, which allows for more flexibility with motherboards. One thing that can probably be considered a glaring omission is the lack of USB 3.0 support. I’m not sure why there were able to include SATA 3.0 and not USB 3.0, considering they had plenty of time to do so. However, pretty much every 890GX board makes use of the abundant PCI-E lanes by adding an auxiliary USB 3.0 controller. Considering it’s a Japanese NEC chip though, these can’t be cheap.

This brings up one major advantage SB850 has over its Intel counterparts: The PCI-E lanes are all “true” full bandwidth 2.0 lanes. Those found on all current Intel Southbridges are 2.0 “compliant” but only run at half bandwidth. This was fine for the longest time, but with the addition of SATA 3.0 and USB 3.0 controllers, 250 MB/s just doesn’t cut it any more. Motherboard manufacturers wanting to add such connectivity to their Intel motherboards have had to come up with some interesting solutions to this. We’ll talk about that more, when we review a P55 board from Gigabyte in the near future.

Out of the two, I think USB 3.0 is far more important (that probably explains why it’s present even on the mATX boards such as the one we’re looking at today). SATA 3.0 just doesn’t make a difference with today’s hard drives (such as the Barracuda XT we reviewed a while back). And if you look, you’ll find that the only drives that do make use of it are ridiculously expensive SSD’s.

So now that we’re familiar with the 890GX chipset, let’s take a closer look at the MSI 890GXM-G65.