Thanks to:
bachus_anonym and bh2k for pictures (please don't take the choice of pictures personally )
Rub87 for input and ideas
The stick of 2700 Samsung TCB3 which died when 5v was put through it during the testing of the mod
Materials required:
LM358 opamp
10k variable resistor (multi-turn)
4.7k fixed resistor
15k fixed resistor
100nf capacitor
some sort of strong glue to attach the variable resistor and opamp to the DDR booster's PCB
A DDR booster!
Additional components for the more complicated mod:
5.1v zener diode (any power rating will be ok)
470ohm fixed resistor
100nf capacitor
Basic mod:
The basic mod is the easiest way to do the regulation mod on the DDR booster. This mod uses a reference voltage which is taken from the 5v rail, so could be influenced by fluctuations on the 5v rail.
1.The first step is to remove the variable resistor (VR) on the DDR booster. If you want to re-use the VR, instead of replacing it with a multi-turn VR, be careful not to damage it whilst removing it.
2.You must now set the VR to work as a voltage divider, which will be used to provide the reference voltage for the Vdimm supply. If you are using a different variable resistor to the original, use a multi-turn type. The 4.7k and 15k fixed resistors are used to make the boosters supply variable between 2.5 to 4.3v. Connect the 15k resistor to ground, and the 4.7k resistor to the 5v supply rail on the booster, as shown in the picture. Connect the variable resistor between the free ends of the 15k and 4.7k resistors. Fix the variable resistor to the boosters PCB using glue ('super glue' as it is known in the UK works well. I think it is called 'crazy glue' in the US, but its a cyanoacrylate based glue)
3.To help stabilize the reference voltage from the voltage divider, you need to connect a 100nf capacitor between the VR's wiper and ground. This also provided 'soft start' to the Vdimm supply to help reduce the inrush current at power-up.
Hi-res picture
4.Next, get your opamp, and attach it to the DDR booster PCB, using the cyanoacrylate based glue based glue. Pin 1 of the opamp will be marked with a dot, or there will be a U shaped notch at the top of the chip - pin 1 will be to the left of the notch with the notch facing upwards. Connect the opamp via pieces of wire as shown in the picture - ground on the boosters power connector to pin 4 (ground on the opamp), 12v to pin 8 on the opamp (the opamps power supply pin), the variable reference voltage from the VR to pin 5 of the opamp (the non-inverting input), the middle pin of where the original variable resistor was connected to pin 7 (the output pin) and the output of the MOSFETs on the booster to pin 6 on the opamp.
Hi-res Pic
If anyone is interested this is the circuit diagram for the basic mod.
Complicated mod:
The more complicated mod uses a regulated voltage which is taken from the 12v rail, so the reference voltage isn't affected by the fluctuation of the voltage rails as much.
1.The first step is the same as the basic mod
2. To produce a regulated voltage for the reference voltage you need to use the 470 ohm resistor and the 5.1v zener diode. Connect the 470 ohm resistor to the 12v rail. Next, connect the end of the zener diode with the bar/stripe to the free end of the 470 ohm resistor. Connect the free end of the zener diode (the free end shouldn't have a stripe on it) to ground. Connect the 100nf capacitor in parallel with the zener diode. This will produce a regulated voltage of 5.1v. Make sure you connect the diode the correct way around otherwise it will produce a 0.7v regulated voltage
Hi-res Pic
3.You must now set the VR to work as a voltage divider, which will be used to provide the reference voltage for the Vdimm supply. If you are using a different variable resistor to the original, use a multi-turn type. The 4.7k and 15k fixed resistors are used to make the boosters supply variable between 2.5 to 4.3v. Connect the 15k resistor to ground, and the 4.7k resistor to the junction between the 470 ohm resistor, zener diode and capacitor, as shown in the picture. Connect the variable resistor between the free ends of the 15k and 4.7k resistors. Fix the variable resistor to the boosters PCB using glue ('super glue' as it is known in the UK works well. I think it is called 'crazy glue' in the US, but its a cyanoacrylate based glue)
Hi-res pic
4.To help stabilize the reference voltage from the voltage divider, you need to connect a 100nf capacitor between the VR's wiper and ground. This also provided 'soft start' to the Vdimm supply to help reduce the inrush current at power-up.
5. Connect the opamp via pieces of wire as shown in the picture - ground on the boosters power connector to pin 4 (ground on the opamp), 12v to pin 8 on the opamp (the opamps power supply pin), the variable reference voltage from the VR to pin 5 of the opamp (the non-inverting input), the middle pin of where the original variable resistor was connected to pin 7 (the output pin) and the output of the MOSFETs on the booster to pin 6 on the opamp.
Hi-res pic
This is the circuit diagram for the more complicated mod.
Before you power up the booster, check all connections (as I'm sure you will all do anyway ). Power up the booster by just plugging in the Molex/ATX connector plugs and not into the motherboard dimm slot, to check that the booster is working properly. Be careful not to let it short on anything when you do this. Check that the booster is producing the required range of voltage when the variable resistor is turned, using a multimeter or the display on the booster.
This is the modded DDR booster. Under load, the droop was found to be 0.01v with 2*256mb sticks of RAM with 3.6v Vdimm on an NF7-s
There are some compatability issues between some motherboards and the modded booster.
These are boards which the modded booster has been found to work with:
Abit NF7-s v2
DFI Lanparty UT NF3
Abit AS8 (Max. displayable voltage on booster and from software is 3.5v)
These are boards which the booster has been found to not work with:
MSI Neo2 (Nf3), however the same board has been found to not work with a un-modded booster, so there could be an issue between other components, and not the modded booster.
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