When I reviewed the Intel DX38BT in January I raised a quizzical eyebrow about its lack of support for the Core 2 Extreme QX9770 processor, which runs on a 1,600MHz front side bus. At the time it seemed like a double whammy as the Taiwanese motherboard manufacturers had added unofficial 1,600MHz support to their X38 designs and as an added kick in the teeth we knew full well that the X48 chipset was just around the corner.
We had already had a look at the MSI X48 Platinum and then reviewed the Gigabyte GA-X48-DQ6 http://www.trustedreviews.com/motherboards/review/2008/02/07/Gigabyte-GA-X48-DQ6/p1 and Asus Rampage. So it seemed fair to have every expectation that the new 1,600MHz front side bus was the next development for Core 2 and the Core 2 Extreme QX9770 was a very encouraging CPU. All told X48 seemed like a big deal and the natural successor to X38.
Well, the time has finally come for Intel to wade in with its DX48BT2 motherboard which in essence is a DX38BT with the addition of support for 1,600MHz DDR3 memory and that all important 1,600MHz front side bus. The obvious comment here is ‘about time too' but things aren't quite that simple. Over the past few months it has become clear that Intel has no plans to release any more Core 2 processors on the faster front side bus before the arrival of Nehalem in Q4. This means that the QX9770 wasn't the start of something wonderful but is to all intents and purposes a reviewer's special - well would you spend £1,000 on one? - so the processors that you are interested in supporting should be a 45nm Penryn Core 2 Duo or Core 2 Quad running on a 1,333MHz front side bus.
Placing the DX38BT and DX48BT2 side-by-side I cannot see a single difference between the two motherboards. Of course you'd expect the two models would be very similar and in many ways that's no bad thing as the layout of the DX38BT is pretty good but there are more oddities yet to come. Take the five passive coolers on the voltage regulators as an example. Intel picks them out on the product brief as having new and improved designs but they look the spitting image of the coolers used on the DX38BT. It's possible that Intel has changed the material that it used for the coolers but I'm prepared to go out on a limb and say that they are the same.
The current BIOS versions for the two models are the same, at 1521, and the various driver versions are also identical so you can read the DX38BT review to get the low-down on the layout of the DX48BT2. The short version is that it's very neat and tidy with support for DDR3 memory and triple PCI Express 2.0 graphics slots with CrossFire but you don't get legacy connectors such as PS/2 ports or a connector for a floppy drive.
As the single new feature with the DX48BT2 is the 1600MHz support for memory and front side bus that's what we'll concentrate on, starting with the Core 2 Extreme QX9650 processor.
This is a quad-core that runs at 3.00GHz on a 1,333MHz front side bus. With most makes of motherboards you can set the memory speed independently of the front side bus but Intel doesn't make life so easy. By default our OCZ PC3-1600 Titanium ran at 1,066MHz and once we fed it the extra voltage that it needed we could run it at 1,333MHz without any problem. The performance varied slightly from previous tests that we ran on the DX38BT when the memory speed had been limited to 1,066MHz but the differences were relatively tiny.