For the first article about the 790GX I decided to cover some of the basics and interpret these results.  A full, comparative review of the Gigabyte board we are using will be coming down the path at a future date, so expect a much more thorough discussion of performance when I have the chance to test in multiple CrossFire and single card configurations.  AMD is also promising some future upgrades for the 790GX platform which will be implemented in upcoming Catalyst releases, so it could be a slightly more interesting platform in the near future.

AMD's 790GX: I'm Down with ACC - Motherboards 31

At this time the ACC functionality must be accessed from the BIOS rather than AMD OverDrive.  However, users can overclock the integrated graphics portion from AOD.

    The Gigabyte 790GX board is our first experience with the platform, but the product name of GA-MA790GP-DSH4 is a bit unwieldy (to say the least).  This board currently sells online for around $139, and it can support Phenoms up to 140 watts TDP.  It is a relatively full featured motherboard which implements all of the 790GX specifications at its highest level (namely 128 MB of SidePort memory running at 1333 MHz).

    This portion is going to cover my impressions of the product, as well as some hard numbers as to its performance.  All is not roses with the 790GX, but as the platform matures and updated drivers and BIOS are available, I am sure many of the issues I have encountered will be fixed.

Test Setup

    I originally had hoped to use a set of DDR-2 1066 DIMMS from Corsair that AMD had initially provided me with their 790FX launch about 9 months ago.  Unfortunately this was not to be.  I was unable to successfully install an OS with the combination of this motherboard and that particular memory.  No matter what I tried with timings, voltage, and default settings the system was a bust.  I then decided to try a set of G-Skill DDR-2 800 DIMMS and everything went swimmingly.

    AMD also provided me with a Phenom 9950 that was fabbed in the 26th week of 2008, which means that it could very well be one of the new 125 watt 9950s that AMD is coming out with.

Gigabyte GA-MA790GP-DSH4 Motherboard
Phenom 9950 @ 2.6 GHz
G-Skill 2 x 2 GB PC6400 @ 4:4:4:12 timings and 2.1v
Samsung 750 GB SATA-II HD
Thermaltake ToughPower 750 Watt PS
Windows Vista Ultimate 64 Bit
Catalyst 8.8 Beta


    Once I figured out that the combination of motherboard/Phenom/memory did not work initially, installation went swimmingly.  Vista loaded without problems, and I was soon up and running in a very basic form.  There are no real standalone southbridge drivers that need installed in Vista.  This does not mean everything is perfect though.  The SB750 southbridge still suffers from the AHCI incompatibility with Vista unless the hotfix from MS is installed… which is problematic with this particular setup unless the user has access to a USB or Firewire hard drive chassis in which they can boot the system with to install the hotfix.  If a user tries to apply the hotfix while the SATA drive is attached to a SB750 port, it will cause Vista to fail to load.  The only workaround to successfully installing the AHCI fix is to install Vista regularly, then transfer the OS hard drive to another boot device (either another SATA controller or use a USB or Firewire hard drive connection).  Boot it from there, apply the hotfix, then restart the computer.  Once Vista has loaded successfully with the SB750 set to AHCI in the BIOS, then the user can shut down the machine and install the hard drive on the native SATA ports.  From there on out AHCI will be enabled.  This becomes increasingly troublesome when a user has a RAID array installed.

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This unwieldy mess is the 790GX board from Gigabyte attached to a 750 watt power supply, with the Thermalright XP90 covering the cooling duties.

    With this particular board and my lack of an external device to boot the system from, I left AHCI disabled in BIOS.  This is likely the situation that most users of this board will run into.

    Once all updates and drivers had been successfully installed, I started assembling the programs that I would be using to see how competent this chipset was in common applications.

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