Thread: In theory (Electrical)

Originally Posted by homchz

I had a very small fanless 500mhz board that ran only on 5v and a ground. Two wires, that is it.

Now I have this AXT board with 20 wires and I wonder why all the mess.

THe board takes 5v? Correct

I have two 5v devices and a 12 volt fan. Nothing that I know of is 3.

In theory can I power just the 5v and 12v lines and have everything work?

How about you give more information about the new board. Also, did you search Google to see if you can figure out what voltages the MB needs.

Michael

I have tired to find the operating voltage on-line but have had no luck as of yet. Though my meter reads 4V at the power switch so I am thinking 5 is right.

Board is a BIOSTAR M7V7IZ

Originally Posted by homchz

I have tired to find the operating voltage on-line but have had no luck as of yet. Though my meter reads 4V at the power switch so I am thinking 5 is right.

Board is a BIOSTAR M7V7IZ

Are you sure that is the board number. I can't find ANYTHING about it.

Michael

My mistake
M7VIZ one less 7

Originally Posted by homchz

I had a very small fanless 500mhz board that ran only on 5v and a ground. Two wires, that is it.

Now I have this AXT board with 20 wires and I wonder why all the mess.

THe board takes 5v? Correct

I have two 5v devices and a 12 volt fan. Nothing that I know of is 3.

In theory can I power just the 5v and 12v lines and have everything work?

you want to hook only 5v and 12v up the atx on the motherboard???

If that is what you are looking to do then no, it will not work. you also need 3.3v -5, and -12 as well as grounds connected to all of the ground connections on the motherboard and a atx power supply has one wire (i beleive the purple one, but you wuold have to look it up) that triggers the power suppply on and off.

sorry if i misunderstood what you were asking.

Nope no misundertanding. Thanks for the info. It is what I figured, just curious as to what the 3V is even for. I appear not to have any 3V accesories.

Originally Posted by homchz

Nope no misundertanding. Thanks for the info. It is what I figured, just curious as to what the 3V is even for. I appear not to have any 3V accesories.

most logic circuits use it.

only since the pentium iii did the processor pull form the 12v rail. and even though it does it still steps the voltage way down. (for instance the athlon 64 venice i have in my desktop is slightly over volted right now at about 1.53v)

3 volt accessories? you do realize that your MOTHERBOARD needs power as well, right? not just your accessories...

plenty of things on the mobo run on 3.3v, and the -5v and -12v rails, although not used all that much, are still required by some parts of the mobo... (the -12v doesn't get used much anymore though)

if you are really curious what rails you can eliminate, try unplugging those wires from the ATX connector. see if it can run without -12v... see if it can run without -5v... then unplug the 3.3v and watch it not run

either way, you're going to end up with at least 3, probably 4 power rails you NEED to use, so a single ATX supply is the best way to go. that 5v motherboard you had probably had on-board DC-DC to generate other voltages as needed.

Or Better yet

http://www.biostar-usa.com/mbdetails.asp?model=m7viz

And I quote

• Hardware Monitor:
CPU Fan Speed
System Voltage
CPU Temperature
System Temperature (Optional)
Vcore,+3.3V,+5V,+12V

Why would it monitor something it does not need.

Also, SDRAM uses 3.3 volts, and Believe DDR does as well. Since that baord only accepts SD or DDR ram, it must use 3.3 volts.

Michael