Consolidated 8RDA+ vDD mod thread.
Well having rooted through that huge thread Jeff started several times over now I got sick and tired of it and compiled it all into one thread to make for easier reading. The words are my own, the pictures are nicked from various sources. Full credit to the guys who figured the mod out - I didnt even have the board at the time. Anyway, on with the show.
The Vdd(chipset) mod described in this thread will VOID YOUR WARRANTY!!! Only attempt the mod if you understand this and are willing to risk damaging your board. PROCEED AT YOUR OWN RISK!!!
First of all make sure you improve drastically on the rather crappy cooling thats provided with the board. Theres plenty of room round the northbridge, and id recommend utilising that even if you decide not to do the vdd mod.
You dont need anything massive, something like an old cheap aluminium heatsink and a nice quiet 60mm fan will do nicely. At 2v the northbridge @ 250mhz (max available but unlikely to get there
OK, on to the modding
Locate the chip in question from the piccys provided. Its the closest 8 pin chip to the dimm slots at the middle of the board side. The pins you need to mod are the ones facing away from the dimm slots, so its nice and easy to solder or use grabbers on them. The VDD (voltage to the nForce2 chipset) is controlled by the IRU3037A chip which is supplying around 1.55-1.6V default on the 8RDA+ board. Pin 1 Fb is connected directly to the output of the switching regulator via resistor divider to provide feedback to the Error amplifier. Therefore if we connect a resistor across Pin 1 Fb to Pin 4 Gnd, we can decrease the resistance and increase the VDD. These pins are the first and last pins on that side.
Id recommend using about 1.88v. In my tests this prooved the most gain from the least voltage. Over this diminishing returns kick in and you see ever smaller fsb increases from using larger steps in voltage. 1.88v gave me a no bullsh*t 100% stable increase of 20mhz on the FSB. From 196mhz dual channel and 202mhz single channel to 216mhz dual channel and 222mhz single channel.
Further mods which I personally figured out include heatsinking the cpu vreg (large chip located behind the PS2 ports) and the 6 voltage mosfets (a strip of 6 chips just behind the serial ports running parallel to the cpu socket) and v+ mosfet (smaller mosfet than the voltage mosfets just behind the ps2 port but infront of the vreg) gained me another 6 - 8mhz stable. This was mostly due to smoothing current out across the voltage lines rather than improving the pure hardware clocking ability of the board. Before this mod I could not use over 2v vcore without random freezes at over 2ghz. After it I am now able to use 2.2v right up to 2.45ghz with no voltage related freezes at all. Below is the area of the board which must be heatsinked up.
Back to the vDD mod.
Heres a rough guide on resistance to voltage increase. I would recommend using a fixed resistor and not an adjustable pot. POTs never give as much signal clarity and tend to have a higher waver of resistance than fixed resistor. Youll get small voltage fluctuations due to their larger inaccuracy.
Default = 1.58v
1k resistor = 1.625v
850ohm resistor = 1.68v
750 ohm resistor = 1.75v
640 ohm resistor = 1.81v
540 ohm resistor = 1.88v
400ohm resistor = 2.0v
120 ohm resistor = 2.2v
As stated in my pm to you I would not suggest going over 1.9v so as to keep the circuit within manufactured tolerances (20%). I am certain that running over 2v will shorten the life of the board, but if this does not concern you go for it
1.58v = 196mhz DC / 202mhz SC
1.625v = 200mhz DC / 207mhz SC
1.68v = 206mhz DC / 212mhz SC
1.75v = 210mhz DC / 216mhz SC
1.81 = 213mhz DC / 220mhz SC
1.88v = 216mhz DC / 222mhz SC (222 I believe is the limit of the corsair stick I was using to test @ 2.9v. This stick does 226mhz at the same volts in an intel system)
2.0v = 218mhz DC / 222mhz SC (and a fairly warm northbridge heatsink)
2.2v = 220mhz DC / 222mhz SC (base of the NB heatsink was BURNING hot).
Your board seems to have a similar initial limit to mine at stock VDD, so id say your results will be pretty similar to mine if not identical.
I would recommend lapping the northbridge and the heatsink youre going to use before fitting. The northbridge is convex as standard (the black surround on mine was a full mm above the metal centre). If you lap the northbridge id recommend going on until you start seeing copper through the tinned surface. This will give you the optimum contact depth. 2mms below that copper is the core itself, so dont go too deep. This is also a good way of checking you have a nice level northbridge. an even spread of copper on the core indicates a nice flat chip. I lap heatsinks as a matter of course anyway. Depending on what heatsink you use it may not be necessary, but 20 minutes of elbow grease always puts my mind at ease that im getting good contact, so I see it as a small price to pay.
To fit the heatsink to the northbridge you can either mark out the heatsink to drill holes to accept the mobo hole spacing, or simply use AS adhesive. I decided to use AS adhesive seeing as im lazy and couldnt be bothered to take the board out of the case
I would also recommend using the stock northbridge heatsink on the southbridge. This thing gets VERY hot (cant touch it for more than a second without burning my finger). the standard northbridge fits the holes around the SB, so its easy to do. The only mod you will have to do is to snap a couple of fins off the stock heatsink (dead easy, just use a pair of grips and move them side to side until they come off) to clear the clock crystal which is right next to the SB.
PiLsY.
[EDIT] Sorry guys - you killed my hosting
[Edit #2] Pics are now hosted courtesy of CTGilles further down the page - thanks m8
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Just hope my soldering skills are up to par! I used to mod playstations and such but i dont know how good I am now.
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