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***zebadee*** · #1 07-02-2006, 05:42 AM

Basic Guide:- PSU.

Below find definitions to help you. In the following post a couple of programs to help you decide how powerful you'll need to go. As a rule of thumb simply go for the biggest/best that you can afford. After all this is the HEART of any system. So don't cut costs here.

PSU: - An electrical system that converts AC current (typical domestic household outlet) into DC current (required by computer circuitry). Known commonly as PSU will typically generate multiple voltages. For example, 12 volts is used for drives with either 3.3 or 5 volts for the circuitry.
N.B. 12 volts often described as Power Rail. Increased demand has resulted in PSUs’ with more than one Power Rail to spread the load. Recommend looking at dual power rails for today’s needs.
New, relatively speaking are PSUs that are described as Modular. These provide detachable cables for neatness & improved airflow etc.
N.B. Make sure you have enough & the right type of connectors for your needs. Try to future proof as far as is possible. (See attachments in posts below).

Glossary of some of the terms used:

Efficiency.
Rate of output power to input power expressed as a percentage

EMI.
(ElectroMagnetic Interference) Noise generated by the switching action of the power supply & other system components. Conducted EMI is radiation reflected back into the power line, which is normally controlled with a line filter. Radiated EMI is that portion that would radiate into free space, but is suppressed by enclosing a power supply’s circuitry in a metal case.

Fan rating.
Airflow rated in cubic feet per minute. A 100% increase in airflow will reduce system operating temperatures by 50% relative to ambient temperatures. For each 18 degrees (Fahrenheit) of reduction, the life of a system is doubled (Arrhenius equation).

Hold-up time.
Time period that a power supply’s output will remain within specified limits, following power disturbances or a loss of input power. Adequate hold-up time keeps the computer running until a standby UPS takes over within a few milliseconds.

Load regulation.
Change in output voltage due to varying load. Expressed as a percent of the normal output voltage, a power supply with tight load regulation delivers optimum voltages regardless of system configuration. This is tested by measuring the difference in output voltage when applying a light load & a heavy load.

Line regulation.
Change in output voltage due to varying input voltage. Expressed as a percent of the normal output voltage, a power supply with tight line regulation delivers optimum voltages throughout the operating range. This is tested by measuring the difference in output voltages while varying the input voltage from minimum to maximum.

MTBF.
(Mean Time Between Failure) Measurement of the relative reliability of a power supply usually based on actual operating data.

Noise (loudness).
Issues include fan blade pitch & speed, hub size, venture depth. Bearing & quality of power supply components. Acoustical noise measured logarithmically; each 3db reduction represents 50% less noise.

Operating range.
Minimum & maximum input voltage limits within which a power supply will operate to specifications. A power supply with a wide range is recommended when the line voltage is subject to brownouts* & surges.

Operating temperature.
Range of ambient temperatures within which a power supply can be safely operated.

Output current.
Maximum current that can be continuously drawn from the output of a power supply. PC motherboards & expansion cards draw 5 volt current. Drive motors draw 12 volts. *

Overcurrent protection.
Circuit that shuts down the power supply from excessive current, including short circuits.

Overvoltage protection.
Circuit that shuts down the power supply if the output voltage exceeds a specified amount.

Power good signal.
Signal used to prevent the computer from starting until stabilised. The power good line switches from 0 to + 5 volts within one tenth to one half second after the power supply reaches normal voltage levels. Whenever low input voltage causes the output voltage to fall below operating levels, the power good signal goes back to zero.

Ripple.
AC voltage superimposed onto the DC output, expressed as a percent of the normal output voltage or as a peak to peak volts. A power supply with clean DC output is essential for computers with high-speed CPUs & memory.

Transient response.
Time required for the output voltage to return within the regulation envelope following a 50% load change. A power supply with a quick response will reduce the risk of read/write errors.

*A lowering of AC power voltage for some period of time. Brownouts can be very harmful to electronic equipment if sustained for long periods. Brownouts can cause flickering or a dimming on screen & the computer may experience intermittent problems as a result.
**High performance cards may exceed this. Hence additional power connector required.

Consider:- Antec, Aopen, Cooler Master, Hyper, Seasonic, Tagan, Thermaltake & Zalman.

***zebadee*** · #2 07-02-2006, 05:49 AM

Hi

Just one of the many programs around for working out how much power is required,
http://www.extreme.outervision.com/psucalculator.jsp
Plus another here.
http://journeysystems.com/power_supply_calculator.php

***zebadee*** · #3 07-08-2006, 04:50 AM

Hi

A look at just one PSU & its connectors.

***zebadee*** · #4 07-08-2006, 04:52 AM

Continued:
Note 2nd fig shows a 4 pin 8 pin combination. 4th fig shows 20 pin to 24 pin combination. For modular cables, take a look here.

**alan1476** · #5 07-08-2006, 11:49 AM

I am wondering, is my Seasonic 600W S-12 Modular? Because I have a lot of cables I do not use. Can they be taken out? Just a thought.

***zebadee*** · #6 07-08-2006, 07:27 PM

Hi

Alan, no your PSU is not modular. Your surplus cables just need tidying up with cable ties. If modular then your PSU would look like attached.

**alan1476** · #7 07-08-2006, 07:40 PM

	Quote:			Originally Posted by zebadee
	Hi Alan, no your PSU is not modular. Your surplus cables just need tidying up with cable ties. If modular then your PSU would look like attached.

Boy those PSUs really are nice, what is the best modular PSU around 600W. I know the Tagan you posted is a good one but obviously I have never seen one but I am going to do some research at Newegg.com. Thanks Zeb

***zebadee*** · #8 07-08-2006, 08:03 PM

Hi

Two schools fo thought here.
1st : - "Conventional" wired PSU's. Manufactureres of such psu's argue that having additional connectors degrades the end reslult. ie putting unnecessary resistance into the line of power transfer.
2nd : - "Modular" manufacturers of these argue that the negatives are so minute because of cable lengths, plus countered by the fact you only use the cables you need.
I've had Hiper "modular" PSU's as well as Seasonic. The Seasonic is by far the better one. In fact the S12 is probably the best in its power class.

**vinman** · #9 07-08-2006, 08:20 PM

http://www.newegg.com/Product/CustRa...agesize=&Page=

Seasonic S12 600W

Apparently the newer ones are at the top of there game last yrs dident fare as well according to these reviews at newegg but now its become one of the best out there! only con I saw was cables supplied were a little messy or not sleved

**Kipper** · #10 07-08-2006, 08:47 PM

	Quote:			Originally Posted by zebadee
	Hi Alan, no your PSU is not modular. Your surplus cables just need tidying up with cable ties. If modular then your PSU would look like attached.

That looks like it would be a CLEAN setup, I like the idea of no loose cables hanging around.

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Basic Guide: PSU