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How to Build a Dual Prime Stable 3.2 DO @ 4.0+ GHz Guaranteed …Many PIX

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Jul 17, 2002
In a Room Heated by Electronics
OK, here the story of my quest to attain a dual prime stable 4Ghz and beyond workstation using only water cooling (no phase change) and a 3.2 Prescott (anything not DPS for 12-24 hours is not 100% stable in my book). I Originally had an Ic7-Max3 MB paired with a 3.0c. I had high hopes of one day pushing it to 4.0+ Ghz but after a few months I knew it was never going to happen. Frustrated, and stuck with my un-utilized Corsair PC-4000 Ram and a 3.0 that would not break 3.7 or so at any sane voltage I decided it was time to sell that pos on eBay (got about $190 for it) and grabbed a D0 Prescott from new egg. Slapped it in and got jammed at 3.8 (and not very stable at that). That ****ed me of real good so I decided to read like a mofo and see what the deal was. Turns out the max3 was at fault with its lame 75 amp limitation. There were people trying to make their way around this limitation tapping the max3 fets for every last ounce of power… but even then they would be out of spec at the approximately 87 Amps required to run a D0 Prescott at 4Ghz (never mind beyond that). Sinking, Doubling up the Caps and, eliminating VDroop were GREAT ideas… but in my mind I figured why take a chance with an attempt at beefing up the weak max3 (even if I did hit 4ghz, with these mods I DOUBT it would handle dual prime for 24 hours, never mind anything over 4ghz flat under a real load) so it was time to hit eBay again and sell my max3 ( $140 Cha-Ching :p lol) just the right amount to buy an IC7-G with the capacity to push 105 amps stock! (Credit to Wauterall for looking up the fet numbers) Now there was board that I would like to add the above listed mods to! A few cap values, and a pin voltage on an IC is different for some of the mods so take note. I saw someone try the droop mod on an IC7-G and nuke it on here somewhere. I kept temperature data, and voltage data at every step of this project so everything accurate.

First I got two bags (16 total) of those OCZ copper ram sinks and used the included thermal tape to attach them to all the front power supply fets. All except 2 of the smaller ones were able to be sinked from the front. I also installed an extra sink on every fet on the rear side of the board. To avoid a short at all costs here use the included thermal tape on the rear as it does not conduct electricity and has less of a chance to short on exposed via’s. I also placed a sink on the Southbridge for fun.

Here are a few tips to save you time here:

1. Do not use the thermal tape on the smaller fets, as they will sag and possibly fall off possibly causing a short. (Mine only sagged, but I did not like the looks of it) use artic silver thermal epoxy to attach to the small ones. It is not as permanent as you might think if you are careful you can freeze them a bit with an air can turned upside down and snap them off later. The included thermal tape is fine for the larger fets and the rear side of the board they will not sag even at 85c+. Dremal away any area of the base or sides that may contact a choke or another sink.

2. Do not sink the ISL6556 IC to the left of the CPU if you ever intend to the VDroop mod (I did the first time and had to snap it off later to get access to the pins) DOH

Next install the caps, the IC7-G uses 3 16v Digikey #493-1791-ND 1200UF ( I believe the max3 uses 16v 2200 which might be helpful in further cleaning the line, but I figured I would stick with the same cap values as the MB had to start with) and 8 6.3v 2200uf digikey 493-1712-ND. Solder them in place matching values and polarity with the front caps. I always use a small dab of hot glue to position the devices before I solder them, this makes for a nice neat job.

Here are some temperatures for you to reflect one 4009 MHz @ 1.55v FET / Cap Temps 20min Dual Prime.

Un-sinked Dual Prime – P1 Fet/P2 Fet/Random Cap Temp 90c/85c/58c!!!
Sinked/Double Fets DP P1 Fet/P2 Fet/Rear Cap Temp 75c/79c/42c
Sinked/Double Fets DP W/Fans P1 Fet/P2 Fet/Rear Cap Temp 44c/36c/27c

As you can see the sinks and caps do help, however I don not like ANYTHING in my comp to be 80c so I added two silent Slim Zalman 80mm fans to the right side panel to blow on the rear of the motherboard directly on the heatsinks and added caps. They tured out to fit VERY nicely :) As you can see by the temps above the fans made a world of difference. I also must note at this point that even after the initial voltage droop on the power supply there was a very slow, gradual drop in Vcore taking up to 20 minutes to flatten out (causing approximately .025 in additional V-Sag) . I later found this directly related to the fet/caps temps. Now that they are kept nice and cool the Vcore steadies in about 2 minutes with nearly no significant drop in voltage.

At this point my system was 100% stable for 24 hours of DP @ 4015, but one thing really bothered me I had to maintain an idle voltage of 1.61 in windows just to get a 30 minute loaded stable core of 1.535 (This was also before I installed the fet cooling fans… so figure in an additional .025v of “my fets are to hot” sag). This is unacceptable! So it was time to implement Master Jedi woutertal’s droop mod. http://www.ocforums.com/showthread.php?p=3212854#post3212854

WARNING! Pin 9 on the IC7-G IS76556 IC is not .5v as it is for the Max3 in woutertal’s tut, on the Ic7-G it is 2.5V, so set your 500k Vof cermet to 500k initially, then work your way down (Don’t start at 100k) or you may be in for trouble.

This mod worked like a charm, and now with that mod in place as well as the active fet cooling my total dual prime droop is .014 over any amount of time. That Sure is better then the .09 roller coaster Vcore I was getting before!! I cant say enough about this droop mod… it owns! You can FINE adjust vcore / droop on the fly with ease.

That about does it. As of now my system is peacefully at 4009Mhz 1.55 Loaded or not heh, 100% rock solid no matter what you try to do to it. I can dual prime at 4.2 with the 5/4 divider, but id rather stay at 4009 250fsb for now. I’m kind of stuck with my lame Corsair PC-4000PRO Does not do much better then 255 at any latency, and I hear it does not care much for over 1.8v so ill stay where I am for now 250 2.5-4-3-5. I am thinking of ebaying it and picking up a pair G.Skill TCCD 4400 Muhahaha ( I love eBay n00bs who pay for my upgrades) then I can really max out my CPU on this setup. I hope this guide helps some people who want 4ghz+ out of a cheap chip as bad as I did. (That is as stable as stock at ANY Stress level).

PS… As for you power supply and cooling I assume you already know not to skip in those areas with this setup.

Cooling- I’m sure you could do this with good air cooling imo Just stay below 50c and I think you will be fine. I like to stay below 40c on water

Power Supply- No need for dual power supplies in this setup! No need for an uber-expensive PC power and cooling 510 either. My secret weapon is an enermax 460 watter that is rated at 33A on the 12v rail (or so claims the white paper) I have had this mofo since my 2.66 Rig and it has never failed me. My current setup Pulls for:

10 Fans (they all run at about 6v so VERY quiet), 2 WD 36gb raptors, 2 Maxtor 300gb, 9800XT, add in cards… And my 12v Rail under full load never drops below 12.30v!

What do you do now that you have a super stable 4.0+ setup? You fold for Team 32 that’s what! :)








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sweet lookin setup you have there, after doing my first unsuccessful attempt at h2o, i have gained a lot of respect to those who get a successful run, and make it look so damn good.
Thanks for all the kind words :)

Alcoholiday said:
Very nice :thup:
The IC7-G motherboard rocks :attn:
What is your AGP voltage set to?

It is set to the max that the board allows 1.65v

dragonhunter said:
Nice!!! have you ever consider becoming a professional case modder? hehe

Lol, with the amount of time I have spent on this box (ifi had to guess from start to finish including design time 50+ hours) I can’t imagine ever building boxes to sell. I did build a sister rig for a friend of mine (exact same setup but in black aluminum… free of charge :p)
oRIDDLERo, what did you have to do to get all of your wiring on the backside of the motherboard tray? I was wanting to hide all of my wiring like that, but wasn't really sure where to start. I see one hole cut in front of the PSU on the top. I have to say that is one incredibly smooth case modding job.