Many members here are very keen to get the most performance out of their rigs.and many have started to take a keen interest in o/cing too.
one of the most important component of a m/c is the psu.it can make or break ur rig.
sadly this is neglected by many people when they plan to purchase a new m/c or upgrade the existing one. They purchase high-end m/b's and Graphic cards with 1GB rams spending about 25K to 30K on it but hesitate to spend even 1/10th of it to purchase a quality psu forgetting that ultimately it is the psu which is going to make them work with stability and without any problems.
recently many members must have read on various websites about the new dual 12V output psu's which have started appearing in the market. here i will attempt , to the best of my ability, what is it ?, and why is it important for "currently avialable" rigs.
here are some of the important points to consider.
1) nearly all the currently avialable m/b's as well as graphics cards get their supply from the 12V line from the psu.
2) effect of temperature on the efficiency of the psu. Translated= the degradation of actual outputs of the psu with rise in temperature.
3) What is printed on the label of the psu is ambiguous. it depends upon how you interpret it. the values are correct and incorrect depending upon theory or practical day to day use.
4) calculation of actual loads (watts) of ur m/c. in brief what ever total you actually get, multiply that by 1.5 to get true requirements.
for e.g. if you total up the rated power consumption of all the components in ur rig. and say it comes to 300 watts. then the actual requirement will be 300 x 1.5 = 450 watts (peak) for a stable and problem free operation of ur m/c.
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Now you see many psu 's with rated output of 17A or 18A on the 12V line. let us consider 17A for our analysis.
1) This 17A is actually calculated at 70 ~ 80 % efficiency of the psu at 25 C temperature. however with rise in temperature the efficiency of the psu reduces drastically. here in our homeland India, the average temperatures are around 32 C and in summers it can reach 38 ~ 40 C easily. plus the components inside the psu also give out a lot of heat hence you must have noticed that there are 2 massive heatsinks inside nearly every psu. it would be safe to assume that the temps inside the psu here in india would be around 45 C to 50C. considering the high ambient temperatures, now at 45 C ~ 50C the efficiency of the psu will decrease and the rated maximum output of 17A on the 12V line will fall about 15 ~ 20 % i.e. to around 14 A.
nb: There are some reputed psu mfg's who give these ratings at 45C or 50C. generally their products are very expensive but thier outputs will not fluctuate no matter how much you load it. (within their rated max specifications obviously)
also consider the loss due to cables and connectors. the conectors (20 pin ATX , 4 pin 12V etc ) and cables do have a small resistance.although this small resistance will seem insignificant to many of you but if you consider the amount of current passing through them (6 to 8 amps per wire) then the loss is quite substantial. I (current) = V (voltge) / R (resistance). in real life situations there is a drop of 250mv to 450 mv. so lets say that 17A maximum output has been reduced to 13A ~ 13.5A maximum output on actual basis.
now lets assume a modern day cpu (average of intel + amd) consumes about 85 to 100 watts (Peak) power. this translates to 7A to 8 A out of the max 13.5A avialable from the psu. ( (W)atts = (V)oltage X Current (I) ) . (note: we have assumed the peak loads. the actual running load will be less , depending upon the programs being used i.e. the cpu load.)
An average graphic card consumes about 35 to 75 watts total (including 5V , 12V , etc...) , so thats 3A to 4A approx. of 12V rail. so our total comes to 10 to 11A.
ps: future cards from Nvidia and ATI will consume about 150 watts !!!! Their power consumption will equal or surpass that of the cpu itself.
now a single HDD + optical drive are rated to consume 1 + 1.5 A = 2.5A of 12V. (optical drives = assuming there is read /write operations. @ idle it consumes very less power ) so our total comes to around 13A
if we consider the floppy, case + psu fans, the cpu cooling fans etc.... Then it is clearly seen that we are already consuming the maximum output of 12V from the psu and even surpassing it momentarily on peak loads.
ps: we have assumed peak loads of all the components . in actual the power consumed by the devices will be lower as not all the components will be using their peak loads simultaneously and continously for a long time. its the reason even a generic 300 watts psu (having 10 to 12A on 12V) will power on and run most of the current systems.
now you, the enthusiast, will wonder why dont the psu mfgr's simply raise the 12V output capability of the psu.....???
for this you have to consider this.
it is generally accepted by the worldwide psu mfgr's that a peak load of 200 watts (+ 10 %) per rail (12v , 5V , 3.3V are the individual rails) is "safe". meaning in case there is a major short circuit in any of the rails then it would not literally catch fire due to the high wattage (current) in them.
it is the reason that most of the psu are limited to 40 ~ 45 amps (5 x 45 = 225 watts) on the 5V line and 17amps (12 x17 = 204 watts) on the 12V line.
kindly note that this 200 ~ 225 watts limitation per rail is not a safety standard per se. but it is "accepted" by most of the psu mfgr's.
There are some psu's from major brands like antec and ocz etc.... which exceed this limit of 200 ~ 225 W , especially on the 12V line. but i guess they must be taking extra precaution and regulations to limit the damage in case of "catastrophic" short or failure.
keeping in view the above two points
1) high consumption of 12V rails.
2) limitation of current carrying capability per rail
the psu mfgr's decided to split the increased 12V load in two seperate rails 12V1 and 12V2. this will increase the output of 12V rail without sacrificing the "safety" limitations. keen observers from amongst the members will also note that even these split dual rails are bound by 17A max load, individually. hence in most of the output ratings you will observe the 12v1 and 12v2 are rated near about 17A each on their top of the line 500~ 600 watts models.
BTW: by dual 12V rail psu's i mean those psu's which have seperate and independent source for the 12V supply. meaning their own diodes, coils and caps and regulation circuitry inside the psu.
There is another reason and benifit of splitting the 12V rails.
the cpu 12V line (12V1) is kept seperate from the other line (12V2) powering the other devices. so any heavy fluctuation in the load or the voltage in one line will not adversely affect other line. this translates to better stability.
deejay's comments:
1) I have purposely omitted giving in-depth technical details.
2) the values i have mentioned above are approximate values. they are used as examples only for the purpose of explaining the workings of the power rails. they are not to be taken literally.
3) E. & O.E. (Errors and Ommissions Expected) : since i am not an electronics student / engineer ..... (whatever). hence kindly do not ask me any technical queries pertaining to above. for that we have many electronics students / engineers on our site who will help you out.
4) inputs and additions from other members to the above is eagerly awaited.
one of the most important component of a m/c is the psu.it can make or break ur rig.
sadly this is neglected by many people when they plan to purchase a new m/c or upgrade the existing one. They purchase high-end m/b's and Graphic cards with 1GB rams spending about 25K to 30K on it but hesitate to spend even 1/10th of it to purchase a quality psu forgetting that ultimately it is the psu which is going to make them work with stability and without any problems.
recently many members must have read on various websites about the new dual 12V output psu's which have started appearing in the market. here i will attempt , to the best of my ability, what is it ?, and why is it important for "currently avialable" rigs.
here are some of the important points to consider.
1) nearly all the currently avialable m/b's as well as graphics cards get their supply from the 12V line from the psu.
2) effect of temperature on the efficiency of the psu. Translated= the degradation of actual outputs of the psu with rise in temperature.
3) What is printed on the label of the psu is ambiguous. it depends upon how you interpret it. the values are correct and incorrect depending upon theory or practical day to day use.
4) calculation of actual loads (watts) of ur m/c. in brief what ever total you actually get, multiply that by 1.5 to get true requirements.
for e.g. if you total up the rated power consumption of all the components in ur rig. and say it comes to 300 watts. then the actual requirement will be 300 x 1.5 = 450 watts (peak) for a stable and problem free operation of ur m/c.
----------------------------------------------------------------------------------------------------------
Now you see many psu 's with rated output of 17A or 18A on the 12V line. let us consider 17A for our analysis.
1) This 17A is actually calculated at 70 ~ 80 % efficiency of the psu at 25 C temperature. however with rise in temperature the efficiency of the psu reduces drastically. here in our homeland India, the average temperatures are around 32 C and in summers it can reach 38 ~ 40 C easily. plus the components inside the psu also give out a lot of heat hence you must have noticed that there are 2 massive heatsinks inside nearly every psu. it would be safe to assume that the temps inside the psu here in india would be around 45 C to 50C. considering the high ambient temperatures, now at 45 C ~ 50C the efficiency of the psu will decrease and the rated maximum output of 17A on the 12V line will fall about 15 ~ 20 % i.e. to around 14 A.
nb: There are some reputed psu mfg's who give these ratings at 45C or 50C. generally their products are very expensive but thier outputs will not fluctuate no matter how much you load it. (within their rated max specifications obviously)
also consider the loss due to cables and connectors. the conectors (20 pin ATX , 4 pin 12V etc ) and cables do have a small resistance.although this small resistance will seem insignificant to many of you but if you consider the amount of current passing through them (6 to 8 amps per wire) then the loss is quite substantial. I (current) = V (voltge) / R (resistance). in real life situations there is a drop of 250mv to 450 mv. so lets say that 17A maximum output has been reduced to 13A ~ 13.5A maximum output on actual basis.
now lets assume a modern day cpu (average of intel + amd) consumes about 85 to 100 watts (Peak) power. this translates to 7A to 8 A out of the max 13.5A avialable from the psu. ( (W)atts = (V)oltage X Current (I) ) . (note: we have assumed the peak loads. the actual running load will be less , depending upon the programs being used i.e. the cpu load.)
An average graphic card consumes about 35 to 75 watts total (including 5V , 12V , etc...) , so thats 3A to 4A approx. of 12V rail. so our total comes to 10 to 11A.
ps: future cards from Nvidia and ATI will consume about 150 watts !!!! Their power consumption will equal or surpass that of the cpu itself.
now a single HDD + optical drive are rated to consume 1 + 1.5 A = 2.5A of 12V. (optical drives = assuming there is read /write operations. @ idle it consumes very less power ) so our total comes to around 13A
if we consider the floppy, case + psu fans, the cpu cooling fans etc.... Then it is clearly seen that we are already consuming the maximum output of 12V from the psu and even surpassing it momentarily on peak loads.
ps: we have assumed peak loads of all the components . in actual the power consumed by the devices will be lower as not all the components will be using their peak loads simultaneously and continously for a long time. its the reason even a generic 300 watts psu (having 10 to 12A on 12V) will power on and run most of the current systems.
now you, the enthusiast, will wonder why dont the psu mfgr's simply raise the 12V output capability of the psu.....???
for this you have to consider this.
it is generally accepted by the worldwide psu mfgr's that a peak load of 200 watts (+ 10 %) per rail (12v , 5V , 3.3V are the individual rails) is "safe". meaning in case there is a major short circuit in any of the rails then it would not literally catch fire due to the high wattage (current) in them.
it is the reason that most of the psu are limited to 40 ~ 45 amps (5 x 45 = 225 watts) on the 5V line and 17amps (12 x17 = 204 watts) on the 12V line.
kindly note that this 200 ~ 225 watts limitation per rail is not a safety standard per se. but it is "accepted" by most of the psu mfgr's.
There are some psu's from major brands like antec and ocz etc.... which exceed this limit of 200 ~ 225 W , especially on the 12V line. but i guess they must be taking extra precaution and regulations to limit the damage in case of "catastrophic" short or failure.
keeping in view the above two points
1) high consumption of 12V rails.
2) limitation of current carrying capability per rail
the psu mfgr's decided to split the increased 12V load in two seperate rails 12V1 and 12V2. this will increase the output of 12V rail without sacrificing the "safety" limitations. keen observers from amongst the members will also note that even these split dual rails are bound by 17A max load, individually. hence in most of the output ratings you will observe the 12v1 and 12v2 are rated near about 17A each on their top of the line 500~ 600 watts models.
BTW: by dual 12V rail psu's i mean those psu's which have seperate and independent source for the 12V supply. meaning their own diodes, coils and caps and regulation circuitry inside the psu.
There is another reason and benifit of splitting the 12V rails.
the cpu 12V line (12V1) is kept seperate from the other line (12V2) powering the other devices. so any heavy fluctuation in the load or the voltage in one line will not adversely affect other line. this translates to better stability.
deejay's comments:
1) I have purposely omitted giving in-depth technical details.
2) the values i have mentioned above are approximate values. they are used as examples only for the purpose of explaining the workings of the power rails. they are not to be taken literally.
3) E. & O.E. (Errors and Ommissions Expected) : since i am not an electronics student / engineer ..... (whatever). hence kindly do not ask me any technical queries pertaining to above. for that we have many electronics students / engineers on our site who will help you out.
4) inputs and additions from other members to the above is eagerly awaited.
