ASRock 939Dual-SATA2 VCore & VDimm Voltmods

Author: W1zzard
Date: 2005-11-04 11:24:14

VDimm Mod

Depending on your needs there are several ways to increase the memory voltage.


The red solder pad carries about 3.20V. If you bridge this solder pad to the VDIMM solder pad with a wire, you will directly feed the 3.20V into your memory.


If you need more voltage, you can route an orange wire (3.3V) from your ATX Power Connector and connect it directly to the solder pad.
This mod is even more useful if you have a PSU with adjustable 3.3V rail, because changing the 3.3V rail will also change your memory voltage. With two memory modules about 3.5A will run through your wire during load, so make sure you do not use a too thin wire.

Variable Voltage

The BIOS setting VDimm controls the transistor "1". If the voltage in the BIOS is set to Normal, the transistor is closed. When set to High, the transistor is open and will drop the voltage seen on Pin 9 of the LM324. The resistance of resistor "2" will determine how big the dropout is.
The smaller the resistance, the higher the dropout, the higher the resulting memory voltage.
What we are going to do now is solder a trimmer to Pin 9 so we create a second dropout which we can manually control. Connect one pin of the variable resistor to Pin 9 and the other pin to Ground (Pin 11 works good, but any ground is fine).
I found a variable resistor of 500 Ohm works best. At 500 Ohm it will increase the memory voltage by 0.25V, this takes the BIOS setting into account.
Resistor at 500 Ohm: BIOS set to Normal results in 2.85V. BIOS set to High results in 2.95V.
The highest memory voltage you can reach with this mod is 3.05V, at 248 Ohm (BIOS Normal) or 316 Ohm (BIOS High).

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