We tested the motherboards with a low power dual core AMD Athlon X2 4850e processor that runs at 2.5GHz and found that the 740G lost out to the 780G in every department. Graphics performance was the most obvious problem as the 780G is just about capable of playing games such as Half Life 2 while the 740G isn't up to the task.
The 740G doesn't support Shader Model 3 graphics but that's more a symptom of the problem than the problem itself as it would only encourage you to set your sights too high. More to the point is the 740G draws an additional 10 Watts of power compared to the 780G at idle which rises to 30W when the system is under load playing a Blu-ray movie. The 780G was perfectly happy operating with the small passive heatsinks on the Gigabyte but with the 740G motherboard we felt it necessary to use a case fan to cool the Northbridge as it hit 50 degrees and was continuing to rise. With the fan the temperature was stable at 40 degrees.
The real shock comes when you look at CPU load during Blu-ray playback as the 740G runs over 75 percent at all times and peaks at 100 percent load. You can see that an anti-virus update or incoming e-mail would interrupt things in those circumstances. By contrast the UVD 2.0 in the 780G chipset keeps the CPU load below 30 percent so you get the dual benefits of a CPU that is unstressed along with lower power consumption.
Plugging in a PCI Express HD 3450 graphics card sorted out Blu-ray playback on the 740G but made little difference to the 780G although it gave us the option of enabling Hybrid Graphics. This combines the 780G graphics core with the HD 3450 in CrossFire. The 780G wins this comparison in every department and makes you wonder who would buy a 740G. Yes it's slightly cheaper than 780G but it removes the option of building a Media Centre PC and takes away Blu-ray playback. It also increases the power draw of your PC, albeit by a small amount.
The AMD 740G chipset is something of a puzzle as it lacks the UVD 2.0 and cannot handle movie playback as well as the 780G yet for some reason the SB700 Southbridge delivers six ports of SATA RAID. That's a bizarre combination of features for a motherboard that is meant to be a natural choice for a Media Centre PC.