G86.. 64 bit/128 bit?

Can someone confirm whether the G86 core, in the 8400M GS has a physical 64 bit memory bus, or is it a 128 bit bus physically, with half of it disabled? I am asking this because if I enable every masked bit through RivaTuner, it shows me a 320 bit memory bus, with 16 shaders. Now, the 16 shaders is very much true, but the 320 bit mem bus clearly isn't. RivaTuner is somewhat buggy with dx10/Vista, so I can't trust it completely. Yet, if it is even partly correct, then it should be possible to turn the 8400GS into a 8400GT. I will be running some tests to find out if it can be done. Rigt now, the bits I enabled to get a reading of a 128 bit bus, turned out to be useless, since it gave me the same score I got at stock, i.e. 1281.

 

my guess would be that its disabled and not architecturally different.

however, even if that is the case, don't expect it to work... if i am right - the 8400m gs and gt come off of the same assembly line. the ones that have a malfunction get the malfunctioned part disabled and packaged as a different chip to keep yields high...

 

If that is the case, I think it might be possible to unlock the bandwidth, albeit with some arifacting, or possible crashes. Certainly worth a try. With some conservative clocks, I can reduce the risks of frying the card...