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Thread: 4PDA2+ REV2.0 vdimm mod

  1. #1
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    4PDA2+ REV2.0 vdimm mod?

    how can i figure out which regulator and pin to mod? i talked to an epox tech on another forum and this is what he told me.

    "It's the eight legged switch spider for non-linear vdimm reg by the left of dimm slots - needs a helping hand by higher referenced voltage or resisted current to ground"

    i couldnt find anything to left of the dimm slots. but there are two on the left side of the socket. i tried to find out the number that is next to chip but have gotten no repsonse.

    im trying to get the vdimm up in the 3.5v-3.6v range. any help would much appreciated

    heres a site that has some pics of the boards layout. if you click on the pics it will increase the resolution linkage
    Last edited by esoteradactyl; 12-02-2003 at 12:49 PM.
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  2. #2
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    Whats the part number of the chip ive circled in red?

    I am the same person that has helped before esoteradactyl (ref - PM)
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  3. #3
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    wow the writing is very small and makes it hard to see when the board is in the case. the numbers being upside down didnt help much either. heres what i got.

    SC2616
    0320
    4G393643
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  4. #4
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    Ok, this chip is MLP package so you cant see the pins, if you cant tell where to solder then ill need a very good high res ipc of the board so I can (hopefully) see myself.

    http://www.semtech.com/pdf/sc2616.pdf

    The FB mod is pretty simple, pin 1 to ground (pin13 or good ground) with a VR, im not sure on values, start high resistance (500k or 1mo) then swap to smaller VR's if there is little or no change.

    Luckily pin 1 should be fairly easily identified, then you just follow the trace to the resistor devider and the mod is simple, you may even be able to swap a SMT resistor with a suitable VR for a cleaner job.

    Im not sure if this will just alter the VDDR or also VBT and other half voltages... testing may be the easyer way to determine this.

  5. #5
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    damn those pins are really small. i dont have the greatest soldering skills, im more of a grabber type user. i was hoping it was like the p4c800 mod i wish somebody else was willing to try this before me. i dont feel like burning up my board by testing it.
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  6. #6
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    Can you see the pins?

    The trick will be to follow the trace from the pin and solder onto a resistor that its linked too, trying to get onto the pins themselves will be nigh on impossible...

  7. #7
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    I had a search for some more pics.

    This is the best I could find, Ive had to enlarge it so its blurry as hell.

    Ive put a dot where I "think" pin 1 is.

    If it is then can you see if a trace from pin 1 meets the 3 components ive circled, if it does which one and where?
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  8. #8
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    i see 2 white lines coming out of the side connecting directly to the 2nd and 3rd divider. the 1st divider being the farthest to right in your pic. pin 1 seems to be a straight line to the 2nd divider. the other comes from and angle that looks like its coming from the opposite side of the chip.
    Last edited by esoteradactyl; 12-02-2003 at 03:16 PM.
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  9. #9
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    you give up??
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  10. #10
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    Not at all.

    If ive understood you correctly the point I have drawn in the below pic is attached to pin 1 of the Vreg.

    If you can measure the resistance of the resistor on the board (or read what it says on top) then we should get a better idea of what VR to use.
    Can you also measure from the point I have drawn to ground and tell me the resistance as well.

    Then the mod is to put a VR between the point I have drawn and ground.. simple.

    EDIT - PIC REMOVED SEE BELOW FOR CORRECT VERSION
    Last edited by Holst; 12-07-2003 at 03:55 PM.

  11. #11
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    I really wonder about this part : With 3.4V max voltage, why do you actually need more?


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  12. #12
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    Bh-5 memory chips will still be increasing....it's up to you if the potenitial for electromagnetic migration is worth it.

  13. #13
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    it would be one more resistor over to the right. its says 905 on the top. now does it need to be soldered to the leg of the resistor on the divider side closest to the vreg? i want to make sure i understand your pic correctly.
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  14. #14
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    Oh sorry, ill change the pic. I didnt quite understand what you meant.

    You want to be soldering from the pin on the Vreg to ground.
    So this means you want to sodler onto the chip side of resistor 905 where I have circled in this pic.
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  15. #15
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    can i just solder to the 905 and then ground anywhere?? or do those 2 points need to be joined together??
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  16. #16
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    No,

    Solder a wire onto that end of R905.. then the VR (set high) then the other end of the VR to ground (motherboard standoff is my prefered place)

    Use a big VR to start (500k) if once you are turned down to 100 there is no change swap for a 100K VR (set high) and repeat untill the voltage changes.

    The other method would be to swap R905 with a VR set to the same value and then just drop the resistance for more voltage.
    This is a nicer method, but is harder soldering.

  17. #17
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    ok i was just confused about your pic pointing to pin1 on the vreg. . so pin1 does not need to be soldered. i will ground the vr to a nearby header. where i can check the vdimm?? i dont know if the bios will read higher than 3.36v
    Last edited by esoteradactyl; 12-08-2003 at 01:13 AM.
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  18. #18
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    We are soldering pin1 but using the resistor as its easyer.
    The result will be the same.

    I think this is the most liely test point for the VDIMM.

    You are right to want to test using a multimeter as these types of mods can often alter the measured values.
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  19. #19
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    that is the vdimm test point. i dont think i will mess with pin1. it is very small. i think soldering to the side of the resistor would be alot easier.
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  20. #20
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    Yep, thats the idea, avoid the near impossible pin soldering and go for the relatively easy resistor.

    Good luck with the mod, should be pretty easy to do with a steady hand.

  21. #21
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    i just wanted to let you know the mod was successful i used a 50k vr. it works fine but the slightest turn and it goes up quite a bit. i need to get either a 100k or 200k. i find it kind of weird though, the psu being modded isnt even needed. i had up to 4.8v available on the vdimm. i set it too 2.6v in the bios and cranked it all the way up to 3.6v
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  22. #22
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    Originally posted by esoteradactyl
    i find it kind of weird though, the psu being modded isnt even needed.
    It's being fed by the 5v line, not the 3.3v one, that's why.


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  23. #23
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    yeah that came to me after i posted its nice because you can set your voltage with the lowest bios setting and use them to set your own range. i have 3.1v-3.8v

    thanks for your help Holst
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  24. #24
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    Kick ass... glad that the mod was successfull.

    This semtech chip is used on several other boards... hopefully the mod will port over easily.

    If you can take some pics of the mod ill write a propper guide.

  25. #25
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    Any word on vref tracking with vdimm?

    3.1v is pretty useless if your vref is only 1.25v. Vref should always be half of vdimm remember?

    My guess would be that Vref comes form a separate IC - the vdimm IC doesnt look like it has enough outputs. It just depends how vref is set. if its set by register linked to vdimm in bios then were in trouble. If its set as 1/2 of vdimm on a strict input/output divider its ok.

    If you want to check vref then run 2 sticks of ram and stick a multimeter in pin1 of one of the empty dimm slots.

    Got the 4PDA2V rev 2.0 here - have taken measurements and vref is always exactly half of the PC health vdimm reading, but im not vdimm modded (dont need more than 2.6v with what im running atm). The exact half of the rail reading would suggest its on a simple divider, but I cant be sure.

    PiLsY.

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