How to volt mod IC7 Vmem

[bmg]

I don't think I've pushed Vmem high enough to where VTT made much of a difference. It makes sense that keeping VTT centered at Vmem/2 would be best, but being a little off doesn't seem to matter much. One thing I did notice is that my Vmem seemed to fluctuate quite a bit when I pushed to to around 3.0V or higher. With VTT centered at Vmem/2 the voltage seems more stable, but that's hard to quantify. If VTT is too low then low to high signal transitions will be slowed slightly. High VTT (not a problem here) would slightly slow the high to low signal transitions.

Here's basically what's involved with the VTT mod. Carefully cut the trace between pin 7 of W83303D and MC50. MC50's pad closest to W83303D pin 7 has a trace connected to it which makes a long trip around the board to the temp/voltage/fan monitoring chip. Next to this MC50 pad is a small via in the board which connects to the VTT voltage. The Vmem approach of just adding resistance between this point and pin 7 (VTT sense, or BT_sen) doesn't work, since the internal resistance to ground of the W83303D pin 7 is too large. Basically I connected small gauge wires to pin 7 and the MC50 pad closest to the W83303D (after cutting the trace connecting them). Mount a 1k pot in a convenient place and connect these wires to it. Solder a fixed resistor (approximately 8k-10k) from pin 7 to ground. I found it convenient to solder it to the pot rather than to pin 7 directly. Increasing the pot's resistance will now increase VTT. Once this pot and the Vmem pot are both set VTT and Vmem will track properly when the voltage is changed in the bios.

This mod will be difficult to do without the proper equipment. Soldering to pin 7 is especially difficult to do without a very fine tipped soldering iron and using magnification. Shorting pin 7 to adjacent pins will probably be disastrous. Obviously cutting the pc trace from pin 7 to MC50 must be done carefully. Standard disclaimers apply.

hipro5, pm or email me your email address and I'll email you the W83303D datasheets.