lehpron
Posts: 6846
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Any Know About Computer Power Supplies?

Sat Mar 24, 2007 5:20 pm

Yes I have tried searching for this, every site I stumble upon seems to follow the only axiom "people don't buy drills, they buy holes."

I actually asked this question on a techie specific forum, the answers I got were watered down and were not what I asked:

What on/connected to the motherboard uses the power from the +3.3v, +5v, +12v, -12v, and 5vsb lines?

Like, I hear the CPU runs off of the 12volt line, correct? etc.
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gkirk
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RE: Any Know About Computer Power Supplies?

Sat Mar 24, 2007 6:08 pm

+3.3V = Chipsets, DIMMS, PCI/AGP cards misc chips
+5v = Disk drive logic, SIMMs, PCI/AGP cards, ISA cards, voltage regulators, misc chips
+12v = Motors, High output voltage regulators


Also you get negative voltage (-5v and -12v).
-5v is routed to the ISA bus on pin B5, thus allowing any ISA card to use the -5v supply. Also, on older floppy controllers, the analog data separator circuits use -5v supply.
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lehpron
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RE: Any Know About Computer Power Supplies?

Sat Mar 24, 2007 6:48 pm

wow, a straight answer, thank you.

Quoting Gkirk (Reply 1):
+3.3V = Chipsets

North and south bridge? Power usage then highly dependant on bandwidth or bus speed?

Quoting Gkirk (Reply 1):
+3.3V = ..., DIMMS

Type of or speed of memory relevant?

Would you happen to know what is the maximum number of watts that can be drawn from the PCI2.0+ slots?
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
TedTAce
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RE: Any Know About Computer Power Supplies?

Sat Mar 24, 2007 7:31 pm

Quoting Gkirk (Reply 1):
+3.3V = Chipsets, DIMMS, PCI/AGP cards misc chips
+5v = Disk drive logic, SIMMs, PCI/AGP cards, ISA cards, voltage regulators, misc chips
+12v = Motors, High output voltage regulators


Also you get negative voltage (-5v and -12v).
-5v is routed to the ISA bus on pin B5, thus allowing any ISA card to use the -5v supply. Also, on older floppy controllers, the analog data separator circuits use -5v supply.

Woah, check out the big brains on Kirkie!!!  thumbsup 
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gkirk
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RE: Any Know About Computer Power Supplies?

Sat Mar 24, 2007 7:37 pm

Quoting TedTAce (Reply 3):
Woah, check out the big brains on Kirkie!!! thumbsup

It helps when you have a degree in Computing  Wink

Quoting Lehpron (Reply 2):

North and south bridge?

Both.

Quoting Lehpron (Reply 2):
Power usage then highly dependant on bandwidth or bus speed?

Yup

Quoting Lehpron (Reply 2):
Type of or speed of memory relevant?

Makes no difference IIRC.

Quoting Lehpron (Reply 2):
Would you happen to know what is the maximum number of watts that can be drawn from the PCI2.0+ slots?

Not off the top of my head  Wink
When you hear the noise of the Tartan Army Boys, we'll be coming down the road!
 
WSOY
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RE: Any Know About Computer Power Supplies?

Mon Mar 26, 2007 2:08 am

Quoting Lehpron (Thread starter):
What on/connected to the motherboard uses the power from the +3.3v, +5v, +12v, -12v, and 5vsb lines?

+3.3V: CPU (re-regulated on-board, CPU can also draw from other supplies), logic (depending on the age of the board), semimodern RAM, earlier AGP versions, modern PCI bus;
+5V, logic (depending on the age of the board), RAM (ending in old SDRAM types) older PCI bus versions;
+12V: used to be needed for RS-232, also required for Intel-standard motherboards (with the additional 4-pin connector.);
-12V: used to needed for RS-232;
5Vsb: required for startup logic (startup button, keyboard/mouse start-up, if any).

There's also a -5V line, but that was dropped from the latest spec, and was in any case a leftover from the very earliest generation of DRAM, and therefore also present on the spec of the ISA bus.

[Edited 2007-03-25 19:33:20]
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WSOY
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RE: Any Know About Computer Power Supplies?

Mon Mar 26, 2007 4:38 am

Quoting Lehpron (Reply 2):
Would you happen to know what is the maximum number of watts that can be drawn from the PCI2.0+ slots?

I take you're asking this purely out of academic interest? I guess you'll find the answer in this document.
http://focus.ti.com/lit/ds/symlink/tps2342.pdf
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lehpron
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RE: Any Know About Computer Power Supplies?

Mon Mar 26, 2007 11:55 am

First off, no TedTAce, this isn't about a TEC. After careful analysis, maintaining a thermoelectric cooler is not worth the delta temperatures.

Quoting WSOY (Reply 6):
I take you're asking this purely out of academic interest?

Just trying to figure out what I'm using, and then, what I can go up to.

My current psu specs say "quoting manual":

max's: +5Vdc@36A, +12Vdc1@20A, +12Vdc2@18A, -12Vdc@0.8A, +5VSB@2.5A, +3.3Vdc@30A;
Total +5V/+3.3V shall be less than 240W
Total +12V1/12V2 shall be less than 360W
Total +5V/+12V/+3.3V shall be less than 560W
MAX power shall be less than 630W

Voltages measured by the EMC6D103 chip on the motherboard reads:
+2.5V: 1.55V
Vcore: 1.22V
+3.3V: 3.32V
+5V: 5.20V
+12V: 12.38V

I want to know how to calculate the maximum processor overclock I can achieve without having to get a bigger power supply. I can't do that without some of the information you folks provided.

All I have is a 95W TDP Intel Pentium D, single optical combo drive, single video card (GeForce 7950GT OC'd 610/840, est. 90W), single PCI sound card (SB Audigy SE), 2 sticks of DDR2 memory, single HDD SATA.

My estimates for power so far is 280 watts, but which rails and how many amps doe I have left?
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
WSOY
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Joined: Tue Jun 13, 2006 10:24 pm

RE: Any Know About Computer Power Supplies?

Mon Mar 26, 2007 8:08 pm

Quoting Lehpron (Reply 7):
I want to know how to calculate the maximum processor overclock I can achieve without having to get a bigger power supply.

Your CPU will shut down due to thermal overload well before your PS runs out of power. Rest assured about it.
"Nukkuessa tulee nälkä" (Nipsu)
 
lehpron
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Joined: Tue Jul 10, 2001 3:42 am

RE: Any Know About Computer Power Supplies?

Tue Mar 27, 2007 1:06 am

Quoting WSOY (Reply 8):
Your CPU will shut down due to thermal overload well before your PS runs out of power. Rest assured about it.

This isn't my first barbeque, just I cannot do anything with my current motherboard. Rather than spend first and complain later, I am informing myself before I drop a dime. I'm a researcher, it's what I do.
The meaning of life is curiosity; we were put on this planet to explore opportunities.

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