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I'm going to describe 2 Vdimm mods for the Shuttle, AN35/N motherboard. The BIOS Vdimm adjust is limited to 2.6 or 2.7V which is not nearly enough for serious overclocking.
The first mod jumps the 3.3V PSU rail to the Vdimm voltage line. The voltage the memory then will see, will be 3.3V This mod has been around for a while, and came from another forum, as did the pictures.
The second mod will set the Vdimm to 3.0V and hasn't been described anywhere that I know of.
The FET that is the focus of attention is shown in this photo:
There are other parts in the circuit, but the basic circuit must look like:
Traced out the circuit somewhat and this is what I get. Some of the value codes don't make sense. Only the 2.6Vdimm computes correctly, but it's hard not having the complete schematic...
Here's a detail of the FET so there's no confusion. Sometimes the center leg that is the Drain, is cut short. As the metal backside of the FET is also the Drain terminal, this doesn't matter. They are connected inside...
The first Vdimm mod is to attach the 3.3V rail to the Vdimm bus. GEIL memory just loves 3.3V. The FET near the DIMM sockets has the legs pointing up, assuming the board is in the normal "cased" position. In this picture, the "Source" lead of the FET is lifted from the PC Board, but it is not necessary to do this.
Here's a picture of the 3.3V Vdimm Mod for the Shuttle AN35/N:
The second Vdimm Mod, sets the Vdimm to 3.0V and may be closer to values that is safe for all memory.
The Mod is accomplished by connecting the Drain and the Source of the Vdimm regulator FET. Here's a picture showing just where to connect. I actually used a set of Mini-Grabber clip test leads to make the connection. They are available at Radio Shack, called "Precision Micro Clip Test Jumpers":
Once again, there is no need to lift any of the leads of any components as both mods are perfectly safe if implemented as shown.... I have tried both mods and measured the Vdimm with a multimeter.... Good luck overclocking...
-------------------- Too Many Computers,... Too Little Time ..... Damn Phenoms! Posts: 24294 | From: Fire Island, NY | Registered: Feb 2003
posted
Thans for the info, and didn't know about that 2nd mod. Knew about the one from the pin 8 on the IC next to the first dimm slot. Your 3volt mod looks easier to do. Bigger connections to work with. What wire size do you reccommend? Looks like you're using about a 16 gauge.
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Polygon, just so I understand the second mod, you're running a jumper fron source to drain correct? Also, does anyone know if Micron Ram can handle 3.0 Vdimm?
posted
Thanks for the help!! Now one other question, could you post a pic of how you connected to the 3.3 rail.I wanna make sure I connect to the right one without having to dig through all my junk, to find my dvm.Think I'm gonna soldier that junmper connection,haven't done any soldiering in awhile, and I'm getting outta practice.
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O.K.,I see where the white wire goes through the hole in the pc board, and is soldiered to the trace of the FET on the bottom but where does the wire connect on the other end, I guess is what I'm asking.
Edit: Nevermind!! I must really need more coffee this morning!!!The second blue pic is showing where the wire is soldered on the bottom of the ATX connector!! dohhhhhhhh
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The "mini alligator" clip, while small enough to fit over just 1 of the FET leads, is impossible to grab the correct 2 because of the bend in the Souce lead...
Turned sideways, the 2 can be grabbed, but then shorting the Gate in the process.....
Now, if I have the circuit correct and there is no "active" pull-up on the gate, shorting all 3 is not a problem... Trouble is I don't have a schematic and don't want to take a chance, even though very small, at joining all 3, and blowing the board...
Anyone want to try shorting all 3...? There is a 95% chance it's no problem.....
-------------------- Too Many Computers,... Too Little Time ..... Damn Phenoms! Posts: 24294 | From: Fire Island, NY | Registered: Feb 2003
posted
Donno about the rest of you, but the 3.0v mod for me is more like 2.83v. When the two pins are connected together, it can only manage around 2.83v. I guess this will help during boot, but it still doesnt get me above 2.8v that 8rdavcore can reach. Gonna try some different settings. More later.
-Plack
-------------------- Lap: Dell Vostro 1500/1.6GHz C2D/4GB RAM/Nvidia 8400GS 128MB/15.4" Desk: E8400 9x433(3.9GHz)@1.35v/Gigabyte G33M-DSR2/4GB RAM/ATi 3850 256MB/37" Westinghouse 1920x1080 My Photo works on Deviant Art Posts: 1313 | From: Hephzibah, GA | Registered: Jan 2004