DFI LanParty NF3 VDimm Mod

Author: Celemine
Date: 2005-08-20 13:56:01

Additional hardware Vdimm-Mod

Datasheet of the chip: http://www.semiconductors.philips.com/acrobat/datasheets/LMX58_A_2904_XX532_4.pdf

I already mentioned that there are unofficial, unsupported BIOS versions that feature up to 4V VDimm. Now you'll perhaps ask, "why should I do the hardware VDimm-Mod then?". The answer is simple. As I explained above the board has cold boot problems when running high Vdimm.
The only way to fix this, is doing this easy hardware mod, that makes the board start with the VDimm that you adjusted via potentiometer, even on the first boot. It let's you adjust the VDimm to your liking and most important with much more precision (BIOS only let's you choose VDimm in steps of 0.1V, while you can adjust it in steps of at least 0.01V with the help of the hardware mod). For this mod you can either use a single 100K potentiometer (precision ~6.67K per full turn), or if you wish to have a little more precision, 2x 50K potentiometers (precision ~3.33K per full turn), connected in series, which again gives you a final resistance of 100K. Both ways will work, but it's up to you, to decide which one you like more. :)

The 100K potentiometer(s) need(s) to be soldered in between pin#3 and pin#8 of the LM358 chip („U28“). Locate the pins according to the datasheet, or just have a look at my pictures and then connect the outer pin of the potentiometer(s) to pin#3 and the middle potentiometer-pin to pin#8 on the LM358 chip. Remember to have the potentiometer(s) set to maximum resistance before powering up your board.

Had to work on the board again today, as it had started to freak out after another additional mod. While fixing this issue I tried something that I had wanted to try from the beginning. I found out that using Pin#2 and Pin#4(Ground) for the Vdimm-Mod also works great. So you can choose between both methods. Either you use the poti between Pin#3 and #8, or you can also use Pin#2 and #4. The combination #2 and #4 is a little better IMHO, because its accessability is simply better. But in the end, the outcome is the same.

In case you might be irritated because you see three potentiometers connected in series on my pics, don't worry, it'll work perfectly with one or two. I only used three first and then just kept it that way, although two would have been enough.

I did the following additional/optional modifications to my board:
  • new chipset heatsink, custom made from an Alpha PAL153U 1U CPU cooler

  • additional heatsinks for several other chips (VCore-MOSFETs, Marvell PHY chip 88SR3020-TBC, ICS93742AF clock buffer etc.; especially the latter two do indeed get quite hot)

  • redid solder-joints for all the capacitors that belong to the VCore- and VDimm-circuits, because they were not perfectly soldered in
And here are the mods in all their glory:

All modifications are done at your own risk! I am not responsible for any damage caused by the modifications described above! Any hardware modification will definitely void your warranty! Keep that in mind.

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