Hi,
I've come up with another mod for IC7 mobo's, not covered in hipro's guide.
One of the problems with vddr mod's is that most motherboards derive their ddr voltage from the 3.3v rail - this means that the maximum stable voltage you can normally get with a mod is about 3.2v.
The current solution for this is to mod the psu sense wire so that you can increase the 3.3v rail to say 3.7v - which is all well and good and does work fairly well.....but there is a problem:
The 3.3v rail supplies more than just the ddr regulators - it supplies numerous chips on the mobo; the PLL FSB chip, the southbridge, the AGP regulator etc.
Increasing the 3.3v rail tends to heat those up quite a bit (hence hipro's need to put heatsinks on the pll chip and the AGP regulator mosfets) and i've found when the 3.3v rail is above 3.6v ish it actually decreases stability (and that AGP mosfet on the ic7 turns into an inferno).
The proper way to solve this problem is to give JUST the vddr regulator mosfets a higher voltage - whilst leaving the 3.3v rail alone. The easiest (altho its hardly an easy mod) is to supply the ddr mosfets from the 5v rail.
To do this you will need to disconnect them from the 3.3v supply (which is actually supplied via another mosfet...more on that in a sec).....Pictures below are the mod i did on my ic7-g, the same mod should work on ic7 and max3 boards:
As you can see the mosfet needs to be desoldered and lifted up to disconnect the back of the mosfet from the mobo - then i simply soldered wires from them direct to the 5v connections on the ATX connector on the back of the board. Finally i added a thermally conductive insulating pad so i could push the mosfets back down, without them shorting back to the 3.3v line they were connected to.
I also added some heatsinks to the mosfets as they no longer fully dissipate thru the mobo - and also get much hotter when on the 5v supply as they have to drop more voltage (after all the w83303d ddr and agp supply is just a linear regulator, not a switching type)
This mod works very well and has made a significant improvement on my stability above 255mhz cas 2, 5-2-2 speeds with my 1gb of xms3500. Atm im rock solid at 260mhz and will be pushing for moreAll this with my 3.3v back to normal without toasting my other mobo components
Btw, for hipro and other hardcore vmod makers, i mentioned earlier that the 3.3v supplied to the DDR mosfets actually comes from another mosfet - for those with the data sheet for the w83303d who r looking at the application circuit, please note that ABIT deviated somewhat from that schematic and decided to supply many other chips from the '3.3vDual' output - which i found out when i simply tried to reroute the 5v there instead....the PLL chip and southbridge got toasty lol. Unfortunately the only safe way to do this mod is as above and disconnect both vddr mosfets from that 3.3vDual source and connect em direct to 5v.
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nice work
Originally Posted by Revv23
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