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How to Power the Memory - Linear Regulator

Just for fun whilst playing around with the H61 MB. The ram was powered by a linear Reg. LT1083, and the power taken from the 3.3V rail of the motherboard.

The MB is H61M-S2V. Its front end is short, therefore, the reg. can be soldered directly to the board (the choke powering the ram needs to be removed). Output pin to the output of choke, Adj pin to Gnd of Cap and Input soldered by a wire to P24 3.3V. Yes, the ram is drawing more than 2.1A of current, the heat sink in the photo is minimum size.

To improve quality of the power source, a choke (those found around the CPU) can be added in series to both the input and output of the reg. respectively. In addition, quality caps should be added in parallel to the both input and output pins. This would greatly reduce switching noise of the 3.3V rail and moderately reduce dissipation of the reg.
Under this config, the reg. output 1.25V which is sufficient for most ram to be used in H61 boards (my Kingston ValueRam will start up at 1.1V). For H55M-UD2H, 2 resistors should be added to adjust the voltage of reg. to 1.3V.


The 3.3V rail has a low usage. Most ATX PS can supply the additional 2.1A for the ram w/o problem. Just try it out as an experiment to hear the difference.






As an aside, have you ever think of a hybrid ATX to linear reg. config. i.e. The ATX 12V powering a 5V reg.(e.g. LT series) for the MB P24, the ATX 5V powering the 3.3V rail of the P24. And more, the P24 3.3V powering a 1.3V reg. for the ram! Then add supplies for the P4 12V and the HDD. With this, you are done with linear Power supply with a bonus of linear PS for the ram. Of course, filtering chokes and caps should be added as mentioned above. This config should be easier to build than conventional linear supply and is cheaper too. You only need to deal with PCBs, probably 2, 4 regulators with heat sink, 8 resistors, some caps and chokes. Just cut off the red, orange and yellow wires, leaving all wire on the P24 plug intact. The multiple Gnd wires need not be cut, just connect the Gnd of regulators to the Gnd of P24 in the MB. No issue of powering sequence or any start up problem whatsoever.

If anyone is interested in building this Hybrid Reg., I can explain in details.




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