Less obviously the X48 uses DDR2 memory instead of the DDR3 support we saw on the X38T-DQ6. On the face of it this is a backwards step as the X38 model supports up to 8GB of DDR3-1600 memory while the X46-DQ6 supports up to 8GB of DDR2-1200. Although 1,200MHz DDR2 sounds significantly slower than 1,600MHz DDR3 there is no apparent impact on performance if you stick with the older technology and it saves you a stack of cash. 2GB of DDR3 costs £140 for good stuff or £200 for excellent stuff yet you can buy 2GB of decent DDR2 for about £80.
The X48 chipset also adds official support for the 1,600MHz front side bus but we hit something of a snag on this front. The X38T-DQ6 performed flawlessly with both the Core 2 Extreme QX9650 on a 1,333MHz front side bus as well as the QX9770 on the faster 1,600MHz front side bus. However, although the X48-DQ6 ran properly with the QX9650 it wouldn't start up with the QX9770 installed, which is somewhat ironic.
The X38T-DQ6 had happily run the Core 2 Extreme QX9770 on an F5 BIOS and continued to do so when we updated to the latest BIOS F6a for this review. The X48-DQ6 was delivered with BIOS F6a already installed and as this motherboard wasn't listed on the Gigabyte support website at the time of the review process there was no option of an update. No doubt a BIOS release will fix this glitch in the X48-DQ6 and while it's hard to get upset when a motherboard won't run a processor that is only available to reviewers it does make you wonder. For goodness sake the X38T can do it so why can't the X48?
Both motherboards offered the same extensive overclocking options including the ability to increase the clock multiplier in an increment of half a step and they both overclocked the QX9650 from 3.00GHz to 3.66GHz.
If you already own an X38 motherboard or specifically own the Gigabyte GA-X38T-DQ6 then you won't be in the market for the GA-X48-DQ6. On the other hand if you're upgrading from a P35 board or older then we'd strongly advise you to go for the X48 instead of the X38T. Cheaper DDR2 memory is a distinct bonus and it gives you the option of buying 4GB of RAM or more so you can run 64-bit Vista. Buying 4GB of DDR3 will cost you a fortune so the DDR3 option realistically limits you to a 32-bit Operating System.
Let's gloss over the fact that the X48-DQ6 wouldn't start with a Core 2 Extreme QX9770 installed. In essence it's a DDR2 version of the X38T-DQ6 with the same admirable build quality and that makes it a highly desirable motherboard.