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8-pin vs 4-pin CPU Power Connector

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January 9, 2011 9:41:05 AM

Hi,

I'm planning on purchasing a Gigabyte GA-880GM-UD2H mobo which will be my platform for an AMD AthlonII X4-640 CPU which is socket AM3. I've looked at various motherboards which supports this CPU and most of them uses only a 4-pin CPU power connector for said CPU. Because the Gigabyte mobo also supports the new Hexa Core X6 AMD CPU it comes with a 8-pin CPU power connector.

Question is,:
Will I damage the AMD AthlonII X4-640 processor if I use the whole 8-pin connector? So far I've managed to figured out the 8-pin power connector is actually 2 x 4-pin connectors, and that the CPU draws about 95watts.
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January 9, 2011 9:42:33 AM

If you have the 8 pin use the 8 pin, it will be fine. :) 
January 9, 2011 10:23:51 AM

Thanks,

I'm still reading up on the subject and it seems it will just create more system stability if the whole 8-pin connector is used. Now to just find a good PSU with the included connector. :) 
Related resources
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January 9, 2011 10:26:04 AM

List your system specs and I'll suggest a few, where in the world are you?
January 9, 2011 12:30:06 PM

The Gigabyte MB I just bought has an 8 pin connector but the PSU I have has a 4 pin. The 4 pin will fit into the 8 pin socket but there are some thoughts that it doesn't provide enough power (or no power at all if the 8 pin connector pins (12V and GND) aren't bridged). Since I couldn't get all 4 cores unlocked on my Phenom X2 555 I tried another PSU with an 8 pin connector but had problems. It would POST but not boot into Windows even when just the two main cores were enabled. I returned it. I bought a 4 pin to 8 pin adapter which uses the PSU's 4 pin connector and a spare 12v (HD or CDROM) connector. I still can't get a 4 cores (can get 3) unlocked but I believe I'm providing enough power to the MB now.
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January 9, 2011 12:45:15 PM

What psu are you using?

If you have a decent psu already with a 4 pin p4 then just use that.

Unlocking is a lottery, its probably nothing to do with the psu, just some cores are faulty to begin with.

My 555 needed +0.025v to be stable at 3.6ghz quad core, but I guess I was lucky.

Try CPU voltage increase up to 1.5v but watch the temps.
January 9, 2011 10:10:34 PM

Ok cool....on it ...found the PSU charts on here and with further research decided on the
SeaSonic S12II-520 Power Supply - 520W. I'm putting together a HTPC ....I've built some PC's b4 which is all about performance, yet with great performance comes great temperatures :)  which is fine for a gaming PC ...but with an HTPC one doesn't really need a dedicated graphix card and with the Gigabyte AMD 880GM chipset all sounds good for Blu-Ray and in general HD Playback. Also adding Kingston Hyper-X 1333mhz 4GB memory Kit in there.

Im sure with said PSU I will still have the option of a dedicated GFX card later on :sol: 
January 9, 2011 10:16:05 PM

beanoslim said:
List your system specs and I'll suggest a few, where in the world are you?



The SeaSonic S12II-520 PSU. I've never used Seasonic before, always stuck to known brands over here like Thermaltake, Antec and such. Taking a dive into the deep end here lol Yet from what I've read about Seasonic it seems pretty good as I don't so much want to spend $200 on a PSU....this one is gonna work me out around $70 which is all good.
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January 10, 2011 5:01:50 AM

I've always heard glowing reviews of SeaSonic. I've been told they also are the manufacturers behind the Antec EarthWatts supplies.

Somewhere else in this forum I read that 90 watts was the guideline barrier between 'needing' the 4-pin or the 8-pin 12VATX connector. I've used the 4-pin in the 8-pin socket if that's all I had. I don't think it was a high-power CPU, so it wasn't taxed. If any 12VATX connector is there... I've found it 100% necessary to put 'something' there. Like mentioned above, the 4->8 splitter doesn't really buy you anything unless you're combining different 'sources'.

Best of luck!
a b à CPUs
January 10, 2011 7:53:37 AM

Seasonic is the best one can get.
a b à CPUs
January 10, 2011 8:51:21 AM

Lourens692 said:
Ok cool....on it ...found the PSU charts on here and with further research decided on the
SeaSonic S12II-520 Power Supply - 520W. I'm putting together a HTPC ....I've built some PC's b4 which is all about performance, yet with great performance comes great temperatures :)  which is fine for a gaming PC ...but with an HTPC one doesn't really need a dedicated graphix card and with the Gigabyte AMD 880GM chipset all sounds good for Blu-Ray and in general HD Playback. Also adding Kingston Hyper-X 1333mhz 4GB memory Kit in there.

Im sure with said PSU I will still have the option of a dedicated GFX card later on :sol: 


Good choice, make sure you get the modular version, it will help in your HTPC.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
January 10, 2011 2:37:39 PM

jpmucha said:
I've always heard glowing reviews of SeaSonic. I've been told they also are the manufacturers behind the Antec EarthWatts supplies.

Somewhere else in this forum I read that 90 watts was the guideline barrier between 'needing' the 4-pin or the 8-pin 12VATX connector. I've used the 4-pin in the 8-pin socket if that's all I had. I don't think it was a high-power CPU, so it wasn't taxed. If any 12VATX connector is there... I've found it 100% necessary to put 'something' there. Like mentioned above, the 4->8 splitter doesn't really buy you anything unless you're combining different 'sources'.

Best of luck!



Thanks jpmucha, I agree if it's got a 8-pin connector ...USE IT! :)  with the cpu drawing 95watts as is I'm sure it will only be beneficial to the system to use the proper rail/plug from the PSU. The 4 to 8 pin splitter doesnt make sense to me either as it only fills all the holes, where the 8-pin or 2x4pin connector has its own dedicated supply through all 8 connector pins.
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January 10, 2011 4:18:06 PM

seasonic is a very good quality powersupply, up there with corsair, thermaltake, nzxt, ect.
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January 10, 2011 5:18:06 PM

Lourens692 said:
Thanks jpmucha, I agree if it's got a 8-pin connector ...USE IT! :)  with the cpu drawing 95watts as is I'm sure it will only be beneficial to the system to use the proper rail/plug from the PSU. The 4 to 8 pin splitter doesnt make sense to me either as it only fills all the holes, where the 8-pin or 2x4pin connector has its own dedicated supply through all 8 connector pins.

I re-read my sentence and I just want to clarify it since it wasn't worded very well...
The other post suggested that 90W was the line that you crossed to need the 8-pin 12VATX instead of the 4-pin being good enough.

From coworkers talking about all the computer issues... quality power supplies are becoming more and more important in a stable working system... Too many stories about $200 CPUs and GPUs becoming fuses for $30 supplies... Build quality over wattage in my book!
a c 99 à CPUs
January 10, 2011 5:39:00 PM

jpmucha said:
I re-read my sentence and I just want to clarify it since it wasn't worded very well...
The other post suggested that 90W was the line that you crossed to need the 8-pin 12VATX instead of the 4-pin being good enough.

From coworkers talking about all the computer issues... quality power supplies are becoming more and more important in a stable working system... Too many stories about $200 CPUs and GPUs becoming fuses for $30 supplies... Build quality over wattage in my book!


AMD Athlon 64 and later CPUs draw all of the CPU power through the +12V auxiliary connector. The 4-pin ATX12V connector is rated to carry 192 watts, not 90. The 8-pin EPS12V adapter is rated for 336 watts. A 95-watt stock Athlon II X4 is not going to overwhelm a 4-pin connection, but a heavily overclocked Phenom II X6 might once you figure in VRM losses, which is why some AM3 boards have an 8-pin connector.

A 4-to-8-pin adapter actually does make sense in some situations. Some motherboards will not boot if you only put a 4-pin plug in an 8-pin socket. If you have a PSU with only a 4-pin adapter and a power consumption under 192 watts, such as in the OP's situation, using an adapter makes perfect sense.
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January 10, 2011 6:59:41 PM

^What MU said. In specifics even if your CPU will work with just 4 pins, 8 pins is preferred since it provides more power and from my experience also is much more stable.

Its like a PSU. Even if you don't need a 800W PSU, it will use less power than getting a PSU thats near the top power usage your system will use.
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January 10, 2011 9:00:42 PM

@MU_Engineer - You sound like you're more in the know. We know that the 95W TDP is more of a CPU cooler thermal dissapation requirement. Of the 192/336W provided by the 4/8-pin aux 12V connectors (respectively), what does a CPU typically draw typically/loaded? I think the post I was referring to was using the 90W TDP as being proportional the actual wattage used at the 12V connector.

@jimmysmitty - I've heard from the effiency curves for 80Plus type requirments that PSUs typically have poor efficiency at low percent utilization. Having a kilowatt PSU running an 100W system might waste more power (overhead circuitry becomes a significant factor for example) than a 400W supply running at 25% load. Too high a load probably starts having heat build-up eat efficiency, so the 800W supply you suggest might be a good idea for a system loading 500-600W.
I'd imagine that looking at the 80Plus curves suggests a 'butter zone' where the supply is allowed to operate loaded where its most efficient, but idles (state where the computer probably is most of the time) above the threshold where its wasteful.
a c 99 à CPUs
January 10, 2011 11:02:05 PM

jpmucha said:
@MU_Engineer - You sound like you're more in the know. We know that the 95W TDP is more of a CPU cooler thermal dissapation requirement. Of the 192/336W provided by the 4/8-pin aux 12V connectors (respectively), what does a CPU typically draw typically/loaded? I think the post I was referring to was using the 90W TDP as being proportional the actual wattage used at the 12V connector.


Maximum power draw from the +12V connector for the Athlon II X4 640 at stock is likely something around 55 watts or so. LostCircuits' testing methodology actually clamps an ammeter to the +12V auxiliary connector, which is exactly what we're talking about here. AMD CPUs draw all of their power through the +12V connector, as does everything else with a 4-pin or 8-pin connector except for Intel LGA115x/1366 parts. They don't test the Athlon II X4 640, but the 645 draws 56 watts and the 630 draws 54.8 watts in their test, so I'd expect the 640 to fall right between there. They do say that their test may not lead to the absolute highest current draw, but it is likely relatively close.
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January 11, 2011 1:21:42 AM

Quote:
A Psu runs its maximum efficiency when its running at 50 percent load. A Psu that have a high rated power can't damage your motherboard because it won't supply power more than needed.

On the other hand a bad psu doesn't matter what power rating its got can damage your hardware

A '2 times what you need' rule feels good as a safety margin... You get good efficiency to start with (under load...let alone idle)... and headroom for when the capacitors begin degrading with time...
And yes... I agree... supply build quality is king.

MU_Engineer said:
Maximum power draw from the +12V connector for the Athlon II X4 640 at stock is likely something around 55 watts or so. LostCircuits' testing methodology actually clamps an ammeter to the +12V auxiliary connector, which is exactly what we're talking about here. AMD CPUs draw all of their power through the +12V connector, as does everything else with a 4-pin or 8-pin connector except for Intel LGA115x/1366 parts. They don't test the Athlon II X4 640, but the 645 draws 56 watts and the 630 draws 54.8 watts in their test, so I'd expect the 640 to fall right between there. They do say that their test may not lead to the absolute highest current draw, but it is likely relatively close.

Good numbers. That's the kind of info I was thinking about. Thanks!
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January 11, 2011 11:11:13 AM

I'd say 2x is a bti overkill... i usually say 50% over load.. my system should run fine on a 500 watt psu so i put a 750 watt corsair on it (up from the corsair tx650w when i only had one gts 450, nwo that 2 sli'd it was best to be safe and bump to the 750)
January 11, 2011 2:19:31 PM

Hey all,

Thanks for all the replies, u've helped alot in my search for my final specs for the HTPC posted below, :

Remote : Compro K300 Remote Control for MCE (Media Center Edition)
PSU : Sea Sonic S12II-520 Power Supply
Motherboard : Gigabyte GA-880GM-USB3
CPU : AMD AthlonII X4-640 Processor- 3.0GHz
HDD : Western Digital Caviar Green - 2TB SATA 3 Gb/s 64 MB Cache
RAM : Kingston Hyper-X Blu KHX1333C9D3B1K2/4G 2x2GB Kit DDR3-1333 1.5v CL9
Optical Drive : LG GH24LS50 DVD Writer SATA
Case : SilverStone Grandia GD05 HTPC Case

Only other thing I ended up not sure of is memory as u get 1,25V (I think) up to 1,65V memory. I ended up downloading the mobo manual and checking the memory intended for the mobo's voltage on there. As we say in the pub ...this is my ABF (absolutely bloody final) specs ...not going for a blu-ray optical drive as Ive got a PS3 and currently doesn't have a need for one.

Thanks again! :) 
!